LM3444MA/NOPB [TI]
交流/直流离线式 LED 驱动器 | D | 8 | -40 to 125;
| 型号： | LM3444MA/NOPB |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | 交流/直流离线式 LED 驱动器 | D | 8 | -40 to 125 驱动 驱动器 |
| 文件： | 总95页 (文件大小：9636K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LM3444
LM3444 AC-DC Offline LED Driver
Literature Number: SNVS682B
November 17, 2011
LM3444
AC-DC Offline LED Driver
General Description
Features
The LM3444 is an adaptive constant off-time AC/DC buck
(step-down) constant current controller that provides a con-
stant current for illuminating high power LEDs. The high fre-
quency capable architecture allows the use of small external
passive components. A passive PFC circuit ensures good
power factor by drawing current directly from the line for most
of the cycle, and provides a constant positive voltage to the
buck regulator. Additional features include thermal shutdown,
current limit and VCC under-voltage lockout. The LM3444 is
available in a low profile MSOP-10 package or an 8 lead SOIC
package.
Application voltage range 80VAC – 277VAC
Capable of controlling LED currents greater than 1A
Adjustable switching frequency
■
■
■
■
■
Low quiescent current
Adaptive programmable off-time allows for constant ripple
current
Thermal shutdown
■
■
■
■
No 120Hz flicker
Low profile 10 pin MSOP package or 8 lead SOIC package
Patent pending drive architecture
Applications
Solid State Lighting
■
■
■
Industrial and Commercial Lighting
Residential Lighting
Typical LM3444 LED Driver Application Circuit
30127505
30127501
© 2011 Texas Instruments Incorporated
301275
www.ti.com
Connection Diagrams
Top View
Top View
30127503
8-Pin SOIC
NS Package Number M08A
30127573
10-Pin MSOP
NS Package Number MUB10A
Ordering Information
NSC Package
Drawing
Order Number
Spec.
Package Type
Top Mark
Supplied As
LM3444MM
LM3444MMX
LM3444MA
LM3444MAX
NOPB
NOPB
NOPB
NOPB
MSOP-10
MSOP-10
SOIC-8
MUB10A
MUB10A
M08A
SZTB
SZTB
1000 Units, Tape and Reel
3500 Units, Tape and Reel
LM3444MA 95 Units, Rail
SOIC-8
M08A
LM3444MA 2500 Units, Tape and Reel
Pin Descriptions
MSOP
SOIC
Name
NC
Description
1
2
3
4
1
No internal connection. Leave this pin open.
No internal connection. Leave this pin open.
No internal connection. Leave this pin open.
NC
NC
8
2
COFF
OFF time setting pin. A user set current and capacitor connected from the output to this pin sets
the constant OFF time of the switching controller.
5
FILTER
Filter input. A low pass filter tied to this pin can filter a PWM dimming signal to supply a DC
voltage to control the LED current. Can also be used as an analog dimming input. If not used for
dimming connect a 0.1µF capacitor from this pin to ground.
6
7
3
4
GND
ISNS
Circuit ground connection.
LED current sense pin. Connect a resistor from main switching MOSFET source, ISNS to GND
to set the maximum LED current.
8
5
GATE
Power MOSFET driver pin. This output provides the gate drive for the power switching MOSFET
of the buck controller.
9
6
7
VCC
NC
Input voltage pin. This pin provides the power for the internal control circuitry and gate driver.
No internal connection. Leave this pin open.
10
www.ti.com
2
ESD Susceptibility
HBM (Note 3)
Junction Temperature (TJ-MAX
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the Texas Instruments Sales Office/
Distributors for availability and specifications.
2 kV
150°C
)
Storage Temperature Range
-65°C to +150°C
Maximum Lead Temp.
Range (Soldering)
VCC and GATE to GND
ISNS to GND
FILTER and COFF to GND
COFF Input Current
Continuous Power Dissipation
(Note 2)
-0.3V to +14V
-0.3V to +2.5V
-0.3V to +7.0V
60mA
260°C
Operating Conditions
VCC
8.0V to 13V
Internally Limited
Junction Temperature
−40°C to +125°C
Electrical Characteristics Limits in standard type face are for TJ = 25°C and those with boldface type apply
over the full Operating Temperature Range ( TJ = −40°C to +125°C). Minimum and Maximum limits are guaranteed through test,
design, or statistical correlation. Typical values represent the most likely parametric norm at TJ = +25ºC, and are provided for
reference purposes only. Unless otherwise stated the following conditions apply: VCC = 12V.
Symbol
VCC SUPPLY
IVCC
Parameter
Conditions
Min Typ
Max Units
Operating supply current
Rising threshold
Falling threshold
Hysterisis
1.58
7.4
2.25
7.7
mA
V
VCC-UVLO
6.0
6.4
1
COFF
VCOFF
Time out threshold
Off timer sinking impedance
Restart timer
1.225 1.276 1.327
V
RCOFF
33
60
Ω
µs
tCOFF
180
CURRENT LIMIT
VISNS
ISNS limit threshold
1.174 1.269 1.364
V
tISNS
Leading edge blanking time
Current limit reset delay
ISNS limit to GATE delay
125
180
33
ns
µs
ns
ISNS = 0 to 1.75V step
CURRENT SENSE COMPARATOR
VFILTER
RFILTER
VOS
FILTER open circuit voltage
720
-4.0
750
1.12
0.1
780
4.0
mV
FILTER impedance
MΩ
mV
Current sense comparator offset voltage
GATE DRIVE OUTPUT
VDRVH
VDRVL
IDRV
GATE high saturation
IGATE = 50 mA
IGATE = 100 mA
GATE = VCC/2
GATE = VCC/2
Cload = 1 nF
0.24
0.22
-0.77
0.88
15
0.50
0.50
V
A
GATE low saturation
Peak souce current
Peak sink current
Rise time
tDV
ns
Fall time
Cload = 1 nF
15
THERMAL SHUTDOWN
TSD Thermal shutdown temperature
Thermal shutdown hysteresis
THERMAL SPECIFICATION
(Note 4)
165
20
°C
RθJA
RθJC
MSOP-10 junction to ambient
MSOP-10 junction to case
124
76
°C/W
Note 1: Absolute maximum ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions for which the device is intended
to be functional, but device parameter specifications may not be guaranteed. For guaranteed specifications and test conditions, see the Electrical Characteristics.
All voltages are with respect to the potential at the GND pin, unless otherwise specified.
Note 2: Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ = 165°C (typ.) and disengages at TJ
= 145°C (typ).
Note 3: Human Body Model, applicable std. JESD22-A114-C.
3
www.ti.com
Note 4: Junction-to-ambient thermal resistance is highly application and board-layout dependent. In applications where high maximum power dissipation exists,
special care must be paid to thermal dissipation issues in board design. In applications where high power dissipation and/or poor package thermal resistance is
present, the maximum ambient temperature may have to be derated. Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction
temperature (TJ-MAX-OP = 125°C), the maximum power dissipation of the device in the application (PD-MAX), and the junction-to ambient thermal resistance of the
part/package in the application (RθJA), as given by the following equation: TA-MAX = TJ-MAX-OP – (RθJA × PD-MAX).
Typical Performance Characteristics
fSW vs Input Line Voltage
Efficiency vs Input Line Voltage
30127504
30127505
VCC UVLO vs Temperature
Min On-Time (tON) vs Temperature
30127507
30127508
www.ti.com
4
Off Threshold (C11) vs Temperature
1.29
Normalized Variation in fSW over VBUCK Voltage
1.28
1.27
1.26
1.25
OFF Threshold at C11
-50 -30 -10 10 30 50 70 90 110130150
TEMPERATURE (°C)
30127510
30127574
Leading Edge Blanking Variation Over Temperature
30127572
5
www.ti.com
Simplified Internal Block Diagram
30127511
FIGURE 1. Simplified Block Diagram
www.ti.com
6
Application Information
Theory of Operation
Refer to Figure 2 below which shows the LM3444 along with
FUNCTIONAL DESCRIPTION
basic external circuitry.
The LM3444 contains all the necessary circuitry to build a line-
powered (mains powered) constant current LED driver.
30127501
FIGURE 2. LM3444 Schematic
7
www.ti.com
VALLEY-FILL CIRCUIT
charged. However, the network of diodes and capacitors
shown between D3 and C10 make up a "valley-fill" circuit. The
valley-fill circuit can be configured with two or three stages.
The most common configuration is two stages. Figure 3 illus-
trates a two and three stage valley-fill circuit.
VBUCK supplies the power which drives the LED string. Diode
D3 allows VBUCK to remain high while V+ cycles on and off.
VBUCK has a relatively small hold capacitor C10 which reduces
the voltage ripple when the valley fill capacitors are being
30127518
FIGURE 3. Two and Three Stage Valley Fill Circuit
The valley-fill circuit allows the buck regulator to draw power
throughout a larger portion of the AC line. This allows the ca-
pacitance needed at VBUCK to be lower than if there were no
valley-fill circuit, and adds passive power factor correction
(PFC) to the application.
pacitors are placed in parallel to each other (Figure 5), and
VBUCK equals the capacitor voltage.
VALLEY-FILL OPERATION
When the “input line is high”, power is derived directly through
D3. The term “input line is high” can be explained as follows.
The valley-fill circuit charges capacitors C7 and C9 in series
(Figure 4) when the input line is high.
30127521
FIGURE 5. Two stage Valley-Fill Circuit when AC Line is
Low
A three stage valley-fill circuit performs exactly the same as
two-stage valley-fill circuit except now three capacitors are
now charged in series, and when the line voltage decreases
to:
30127519
FIGURE 4. Two stage Valley-Fill Circuit when AC Line is
High
The peak voltage of a two stage valley-fill capacitor is:
Diode D3 is reversed biased and three capacitors are in par-
allel to each other.
The valley-fill circuit can be optimized for power factor, volt-
age hold up and overall application size and cost. The
LM3444 will operate with a single stage or a three stage val-
ley-fill circuit as well. Resistor R8 functions as a current
limiting resistor during start-up, and during the transition from
series to parallel connection. Resistors R6 and R7 are 1 MΩ
bleeder resistors, and may or may not be necessary for each
application.
As the AC line decreases from its peak value every cycle,
there will be a point where the voltage magnitude of the AC
line is equal to the voltage that each capacitor is charged. At
this point diode D3 becomes reversed biased, and the ca-
www.ti.com
8
BUCK CONVERTER
voltage, transistor Q2 is turned off and diode D10 conducts
the current through the inductor and LEDs. Capacitor C12
eliminates most of the ripple current seen in the inductor. Re-
sistor R4, capacitor C11, and transistor Q3 provide a linear
current ramp that sets the constant off-time for a given output
voltage.
The LM3444 is a buck controller that uses a proprietary con-
stant off-time method to maintain constant current through a
string of LEDs. While transistor Q2 is on, current ramps up
through the inductor and LED string. A resistor R3 senses this
current and this voltage is compared to the reference voltage
at FILTER. When this sensed voltage is equal to the reference
30127523
FIGURE 6. LM3444 Buck Regulation Circuit
OVERVIEW OF CONSTANT OFF-TIME CONTROL
the ISNS pin. This sensed voltage across R3 is compared
against the voltage of FILTER, at which point Q2 is turned off
by the controller.
A buck converter’s conversion ratio is defined as:
Constant off-time control architecture operates by simply
defining the off-time and allowing the on-time, and therefore
the switching frequency, to vary as either VIN or VO changes.
The output voltage is equal to the LED string voltage (VLED),
and should not change significantly for a given application.
The input voltage or VBUCK in this analysis will vary as the
input line varies. The length of the on-time is determined by
the sensed inductor current through a resistor to a voltage
reference at a comparator. During the on-time, denoted by
tON, MOSFET switch Q2 is on causing the inductor current to
30127525
increase. During the on-time, current flows from VBUCK
,
through the LEDs, through L2, Q2, and finally through R3 to
ground. At some point in time, the inductor current reaches a
maximum (IL2-PK) determined by the voltage sensed at R3 and
FIGURE 7. Inductor Current Waveform in CCM
9
www.ti.com
During the off-period denoted by tOFF, the current through L2
continues to flow through the LEDs via D10.
THERMAL SHUTDOWN
With efficiency of the buck converter in mind:
Substitute equations and rearrange:
Thermal shutdown limits total power dissipation by turning off
the output switch when the IC junction temperature exceeds
165°C. After thermal shutdown occurs, the output switch
doesn’t turn on until the junction temperature drops to ap-
proximately 145°C.
Design Guide
DETERMINING DUTY-CYCLE (D)
Duty cycle (D) approximately equals:
Off-time, and switching frequency can now be calculated us-
ing the equations above.
With efficiency considered:
SETTING THE SWITCHING FREQUENCY
Selecting the switching frequency for nominal operating con-
ditions is based on tradeoffs between efficiency (better at low
frequency) and solution size/cost (smaller at high frequency).
The input voltage to the buck converter (VBUCK) changes with
both line variations and over the course of each half-cycle of
the input line voltage. The voltage across the LED string will,
however, remain constant, and therefore the off-time remains
constant.
For simplicity, choose efficiency between 75% and 85%.
CALCULATING OFF-TIME
The “Off-Time” of the LM3444 is set by the user and remains
fairly constant as long as the voltage of the LED stack remains
constant. Calculating the off-time is the first step in determin-
ing the switching frequency of the converter, which is integral
in determining some external component values.
The on-time, and therefore the switching frequency, will vary
as the VBUCK voltage changes with line voltage. A good design
practice is to choose a desired nominal switching frequency
knowing that the switching frequency will decrease as the line
voltage drops and increase as the line voltage increases
(Figure 8).
PNP transistor Q3, resistor R4, and the LED string voltage
define a charging current into capacitor C11. A constant cur-
rent into a capacitor creates a linear charging characteristic.
Resistor R4, capacitor C11 and the current through resistor
R4 (iCOLL), which is approximately equal to VLED/R4, are all
fixed. Therefore, dv is fixed and linear, and dt (tOFF) can now
be calculated.
Common equations for determining duty cycle and switching
frequency in any buck converter:
30127510
FIGURE 8. Graphical Illustration of Switching Frequency
vs VBUCK
The off-time of the LM3444 can be programmed for switching
frequencies ranging from 30 kHz to over 1 MHz. A trade-off
between efficiency and solution size must be considered
when designing the LM3444 application.
The maximum switching frequency attainable is limited only
by the minimum on-time requirement (200 ns).
Therefore:
www.ti.com
10
Worst case scenario for minimum on time is when VBUCK is at
its maximum voltage (AC high line) and the LED string voltage
(VLED) is at its minimum value.
VL(ON-TIME) = VBUCK - VLED
During the off-time, the voltage seen by the inductor is ap-
proximately:
VL(OFF-TIME) = VLED
The value of VL(OFF-TIME) will be relatively constant, because
the LED stack voltage will remain constant. If we rewrite the
equation for an inductor inserting what we know about the
circuit during the off-time, we get:
The maximum voltage seen by the Buck Converter is:
INDUCTOR SELECTION
The controlled off-time architecture of the LM3444 regulates
the average current through the inductor (L2), and therefore
the LED string current. The input voltage to the buck converter
(VBUCK) changes with line variations and over the course of
each half-cycle of the input line voltage. The voltage across
the LED string is relatively constant, and therefore the current
through R4 is constant. This current sets the off-time of the
converter and therefore the output volt-second product
(VLED x off-time) remains constant. A constant volt-second
product makes it possible to keep the ripple through the in-
ductor constant as the voltage at VBUCK varies.
Re-arranging this gives:
From this we can see that the ripple current (Δi) is proportional
to off-time (tOFF) multiplied by a voltage which is dominated
by VLED divided by a constant (L2).
These equations can be rearranged to calculate the desired
value for inductor L2.
Where:
Finally:
30127540
Refer to “Design Example” section of the datasheet to better
understand the design process.
FIGURE 9. LM3444 External Components of the Buck
Converter
SETTING THE LED CURRENT
The equation for an ideal inductor is:
The LM3444 constant off-time control loop regulates the peak
inductor current (IL2). The average inductor current equals the
average LED current (IAVE). Therefore the average LED cur-
rent is regulated by regulating the peak inductor current.
Given a fixed inductor value, L, this equation states that the
change in the inductor current over time is proportional to the
voltage applied across the inductor.
During the on-time, the voltage applied across the inductor is,
VL(ON-TIME) = VBUCK - (VLED + VDS(Q2) + IL2 x R3)
Since the voltage across the MOSFET switch (Q2) is rela-
tively small, as is the voltage across sense resistor R3, we
can simplify this to approximately,
11
www.ti.com
The valley fill capacitors should be sized to supply energy to
the buck converter (VBUCK) when the input line is less than its
peak divided by the number of stages used in the valley fill
(tX). The capacitance value should be calculated for the max-
imum LED current.
30127525
FIGURE 10. Inductor Current Waveform in CCM
Knowing the desired average LED current, IAVE and the nom-
inal inductor current ripple, ΔiL, the peak current for an appli-
cation running in continuous conduction mode (CCM) is
defined as follows:
30127552
FIGURE 11. Two Stage Valley-Ffill VBUCK Voltage
From the above illustration and the equation for current in a
capacitor, i = C x dV/dt, the amount of capacitance needed at
VBUCK will be calculated as follows:
Or the LED current would then be,
At 60Hz, and a valley-fill circuit of two stages, the hold up time
(tX) required at VBUCK is calculated as follows. The total angle
of an AC half cycle is 180° and the total time of a half AC line
cycle is 8.33 ms. When the angle of the AC waveform is at
30° and 150°, the voltage of the AC line is exactly ½ of its
peak. With a two stage valley-fill circuit, this is the point where
the LED string switches from power being derived from AC
line to power being derived from the hold up capacitors (C7
and C9). 60° out of 180° of the cycle or 1/3 of the cycle the
power is derived from the hold up capacitors (1/3 x 8.33 ms
= 2.78 ms). This is equal to the hold up time (dt) from the
above equation, and dv is the amount of voltage the circuit is
allowed to droop. From the next section (“Determining Maxi-
mum Number of Series Connected LEDs Allowed”) we know
the minimum VBUCK voltage will be about 45V for a 90VAC to
135VAC line. At 90VAC low line operating condition input, ½ of
the peak voltage is 64V. Therefore with some margin the volt-
age at VBUCK can not droop more than about 15V (dv). (i) is
equal to (POUT/VBUCK), where POUT is equal to (VLED x ILED).
Total capacitance (C7 in parallel with C9) can now be calcu-
lated. See “ Design Example" section for further calculations
of the valley-fill capacitors.
This is important to calculate because this peak current mul-
tiplied by the sense resistor R3 will determine when the
internal comparator is tripped. The internal comparator turns
the control MOSFET off once the peak sensed voltage reach-
es 750 mV.
Current Limit: The trip voltage on the PWM comparator is
750 mV. However, if there is a short circuit or an excessive
load on the output, higher than normal switch currents will
cause a voltage above 1.27V on the ISNS pin which will trip
the I-LIM comparator. The I-LIM comparator will reset the RS
latch, turning off Q2. It will also inhibit the Start Pulse Gener-
ator and the COFF comparator by holding the COFF pin low.
A delay circuit will prevent the start of another cycle for 180
µs.
Determining Maximum Number of Series Connected
LEDs Allowed:
The LM3444 is an off-line buck topology LED driver. A buck
converter topology requires that the input voltage (VBUCK) of
the output circuit must be greater than the voltage of the LED
stack (VLED) for proper regulation. One must determine what
the minimum voltage observed by the buck converter will be
before the maximum number of LEDs allowed can be deter-
mined. Two variables will have to be determined in order to
accomplish this.
VALLEY FILL CAPACITORS
Determining voltage rating and capacitance value of the val-
ley-fill capacitors:
The maximum voltage seen by the valley-fill capacitors is:
1. AC line operating voltage. This is usually 90VAC to
135VAC for North America. Although the LM3444 can
operate at much lower and higher input voltages a range
is needed to illustrate the design process.
This is, of course, if the capacitors chosen have identical ca-
pacitance values and split the line voltage equally. Often a
20% difference in capacitance could be observed between
like capacitors. Therefore a voltage rating margin of 25% to
50% should be considered.
2. How many stages are implemented in the valley-fill circuit
(1, 2 or 3).
In this example the most common valley-fill circuit will be used
(two stages).
Determining the capacitance value of the valley-fill ca-
pacitors:
www.ti.com
12
that all of the ripple will be seen by the capacitor, and not the
LEDs. One must ensure that the capacitor you choose can
handle the RMS current of the inductor. Refer to
manufacture’s datasheets to ensure compliance. Usually an
X5R or X7R capacitor between 1 µF and 10 µF of the proper
voltage rating will be sufficient.
SWITCHING MOSFET
The main switching MOSFET should be chosen with efficien-
cy and robustness in mind. The maximum voltage across the
switching MOSFET will equal:
30127554
The average current rating should be greater than:
FIGURE 12. AC Line
IDS-MAX = ILED(-AVE)(DMAX
)
Figure 12 shows the AC waveform. One can easily see that
the peak voltage (VPEAK) will always be:
RE-CIRCULATING DIODE
The LM3444 Buck converter requires a re-circulating diode
D10 (see the Typical Application circuit Figure 2) to carry the
inductor current during the MOSFET Q2 off-time. The most
efficient choice for D10 is a diode with a low forward drop and
near-zero reverse recovery time that can withstand a reverse
voltage of the maximum voltage seen at VBUCK. For a common
110VAC ± 20% line, the reverse voltage could be as high as
190V.
The voltage at VBUCK with a valley fill stage of two will look
similar to the waveforms of Figure 11.
The purpose of the valley fill circuit is to allow the buck con-
verter to pull power directly off of the AC line when the line
voltage is greater than its peak voltage divided by two (two
stage valley fill circuit). During this time, the capacitors within
the valley fill circuit (C7 and C8) are charged up to the peak
of the AC line voltage. Once the line drops below its peak
divided by two, the two capacitors are placed in parallel and
deliver power to the buck converter. One can now see that if
the peak of the AC line voltage is lowered due to variations in
the line voltage the DC offset (VDC) will lower. VDC is the low-
est value that voltage VBUCK will encounter.
The current rating must be at least:
ID = 1 - (DMIN) x ILED(AVE)
Or:
Design Example
Example:
The following design example illustrates the process of cal-
culating external component values.
Line voltage = 90VAC to 135VAC
Valley-Fill = two stage
Known:
1. Input voltage range (90VAC – 135VAC
2. Number of LEDs in series = 7
)
3. Forward voltage drop of a single LED = 3.6V
4. LED stack voltage = (7 x 3.6V) = 25.2V
Choose:
1. Nominal switching frequency, fSW-TARGET = 250 kHz
2. ILED(AVE) = 400 mA
Depending on what type and value of capacitors are used,
some derating should be used for voltage droop when the
capacitors are delivering power to the buck converter. With
this derating, the lowest voltage the buck converter will see is
about 42.5V in this example.
3.
Δi (usually 15% - 30% of ILED(AVE)) = (0.30 x 400 mA) =
120 mA
To determine how many LEDs can be driven, take the mini-
mum voltage the buck converter will see (42.5V) and divide it
by the worst case forward voltage drop of a single LED.
4. Valley fill stages (1,2, or 3) = 2
5. Assumed minimum efficiency = 80%
Calculate:
Example: 42.5V/3.7V = 11.5 LEDs (11 LEDs with margin)
1. Calculate minimum voltage VBUCK equals:
OUTPUT CAPACITOR
A capacitor placed in parallel with the LED or array of LEDs
can be used to reduce the LED current ripple while keeping
the same average current through both the inductor and the
LED array. With a buck topology the output inductance (L2)
can now be lowered, making the magnetics smaller and less
expensive. With a well designed converter, you can assume
2. Calculate maximum voltage VBUCK equals:
13
www.ti.com
8. Calculate C11:
9.
3. Calculate tOFF at VBUCK nominal line voltage:
10. Use standard value of 120 pF
11. Calculate ripple current: 400 mA X 0.30 = 120 mA
12. Calculate inductor value at tOFF = 3 µs:
4. Calculate tON(MIN) at high line to ensure that
tON(MIN) > 200 ns:
13. Choose C10: 1.0 µF 200V
14. Calculate valley-fill capacitor values: VAC low line =
90VAC, VBUCK minimum equals 60V. Set droop for 20V
maximum at full load and low line.
5. Calculate C11 and R4:
6. Choose current through R4: (between 50 µA and 100 µA)
70 µA
i) equals POUT/VBUCK (270 mA), dV equals 20V, dt equals
2.77 ms, and then CTOTAL equals 37 µF. Therefore C7 =
C9 = 22 µF
7. Use a standard value of 365 kΩ
www.ti.com
14
LM3444 Design Example 1
Input = 90VAC to 135VAC, VLED = 7 x HB LED String Application @ 400 mA
30127569
15
www.ti.com
Bill of Materials
Qty
1
Ref Des
U1
Description
Mfr
Mfr PN
LM3444MM
HD04-T
IC, CTRLR, DRVR-LED, MSOP10
Bridge Rectifiier, SMT, 400V, 800 mA
NSC
1
BR1
L1
DiodesInc
Panasonic
1
Common mode filter DIP4NS, 900 mA, 700
µH
ELF-11090E
1
2
1
3
L2
L3, L4
Inductor, SHLD, SMT, 1A, 470 µH
Diff mode inductor, 500 mA 1 mH
Coilcraft
Coilcraft
MSS1260-474-KLB
MSS1260-105KL-KLB
HI1206T161R-10
L5
Steward
Bead Inductor, 160Ω, 6A
Cap, Film, X2Y2, 12.5MM, 250VAC, 20%, 10
nF
C1, C2, C15
Panasonic
ECQ-U2A103ML
1
2
2
1
1
1
1
2
4
1
1
1
1
1
2
2
1
1
2
1
1
1
C4
C5, C6
C7, C9
C10
Cap, X7R, 0603, 16V, 10%, 100 nF
Cap, X5R, 1210, 25V, 10%, 22 µF
Cap, AL, 200V, 105C, 20%, 33 µF
Cap, Film, 250V, 5%, 10 nF
Cap, X7R, 1206, 50V, 10%, 1.0 uF
Cap, C0G, 0603, 100V, 5%, 120 pF
Diode, ZNR, SOT23, 15V, 5%
Diode, SCH, SOD123, 40V, 120 mA
Diode, FR, SOD123, 200V, 1A
Diode, FR, SMB, 400V, 1A
MuRata
MuRata
UCC
GRM188R71C104KA01D
GRM32ER61E226KE15L
EKXG201ELL330MK20S
B32521C3103J
Epcos
C12
Kemet
C1206F105K5RACTU
GRM1885C2A121JA01D
BZX84C15LT1G
BAS40H
C11
MuRata
OnSemi
NXP
D1
D2, D13
D3, D4, D8, D9
D10
Rohm
RF071M2S
OnSemi
Fairchild
Panasonic
Panasonic
Panasonic
Rohm
MURS140T3G
D12
TVS, VBR = 144V
SMBJ130CA
R2
ERJ-8ENF1003V
ERJ-14RQJ1R8U
ERJ-3EKF5763V
MCR10EZHF1004
RC1206JR-070RL
Resistor, 1206, 1%, 100 kΩ
Resistor, 1210, 5%, 1.8Ω
Resistor, 0603, 1%, 576 kΩ
Resistor, 0805, 1%, 1.00 MΩ
Resistor, 1206, 0.0Ω
R3
R4
R6, R7
R8, R10
R9
Yageo
Resistor, 1812, 0.0Ω
RT1
Thermometrics
Fairchild
CL-140
FQD7N30TF
MMBTA92
1715721
Thermistor, 120V, 1.1A, 50Ω @ 25°C
XSTR, NFET, DPAK, 300V, 4A
XSTR, PNP, SOT23, 300V, 500 mA
Terminal Block 2 pos
Q1, Q2
Q3
Fairchild
J1
Phoenix Contact
bel
F1
Fuse, 125V, 1,25A
SSQ 1.25
www.ti.com
16
Physical Dimensions inches (millimeters) unless otherwise noted
MSOP-10 Pin Package (MM)
For Ordering, Refer to Ordering Information Table
NS Package Number MUB10A
SOIC-8 Pin Package (M)
For Ordering, Refer to Ordering Information Table
NS Package Number M08A
17
www.ti.com
Notes
TI/NATIONAL INTERIM IMPORTANT NOTICE
Texas Instruments has purchased National Semiconductor. As of Monday, September 26th, and until further notice, products sold or
advertised under the National Semiconductor name or logo, and information, support and interactions concerning such products, remain
subject to the preexisting National Semiconductor standard terms and conditions of sale, terms of use of website, and Notices (and/or
terms previously agreed in writing with National Semiconductor, where applicable) and are not subject to any differing terms and notices
applicable to other TI components, sales or websites. To the extent information on official TI and National websites and business social
networking media, etc., pertains to both TI and National-branded products, both companies' instructions, warnings and limitations in the
above-referenced terms of use apply.
Following are URLs where you can obtain information on other Texas Instruments products and application solutions:
Products
Applications
Communications and Telecom
Computers and Peripherals
Audio
www.ti.com/audio
amplifier.ti.com
www.ti.com/communications
www.ti.com/computers
www.ti.com/consumer-apps
www.ti.com/energy
Amplifiers
Data Converters
DLP® Products
DSP
dataconverter.ti.com Consumer Electronics
www.dlp.com
dsp.ti.com
Energy and Lighting
Industrial
www.ti.com/industrial
www.ti.com/medical
Clocks and Timers
Interface
www.ti.com/clocks
interface.ti.com
logic.ti.com
Medical
Security
www.ti.com/security
Logic
Space, Avionics and Defense
www.ti.com/space-avionics-
defense
Power Mgmt
Microcontrollers
RFID
power.ti.com
Transportation and Automotive www.ti.com/automotive
microcontroller.ti.com Video and Imaging
www.ti-rfid.com Wireless
www.ti.com/video
www.ti.com/wireless-apps
RF/IF and ZigBee® Solutions www.ti.com/lprf
TI E2E Community Home Page e2e.ti.com
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright© 2011 Texas Instruments Incorporated
www.ti.com
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements,
and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should
obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are
sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard
warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where
mandated by government requirements, testing of all parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and
applications using TI components. To minimize the risks associated with customer products and applications, customers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right,
or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information
published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a
warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual
property of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied
by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive
business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional
restrictions.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all
express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not
responsible or liable for any such statements.
TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably
be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing
such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products
and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be
provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in
such safety-critical applications.
TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are
specifically designated by TI as military-grade or "enhanced plastic." Only products designated by TI as military-grade meet military
specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at
the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use.
TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are
designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated
products in automotive applications, TI will not be responsible for any failure to meet such requirements.
Following are URLs where you can obtain information on other Texas Instruments products and application solutions:
Products
Audio
Applications
www.ti.com/audio
amplifier.ti.com
dataconverter.ti.com
www.dlp.com
Communications and Telecom www.ti.com/communications
Amplifiers
Data Converters
DLP® Products
DSP
Computers and Peripherals
Consumer Electronics
Energy and Lighting
Industrial
www.ti.com/computers
www.ti.com/consumer-apps
www.ti.com/energy
dsp.ti.com
www.ti.com/industrial
www.ti.com/medical
www.ti.com/security
Clocks and Timers
Interface
www.ti.com/clocks
interface.ti.com
logic.ti.com
Medical
Security
Logic
Space, Avionics and Defense www.ti.com/space-avionics-defense
Transportation and Automotive www.ti.com/automotive
Power Mgmt
Microcontrollers
RFID
power.ti.com
microcontroller.ti.com
www.ti-rfid.com
Video and Imaging
www.ti.com/video
OMAP Mobile Processors www.ti.com/omap
Wireless Connectivity www.ti.com/wirelessconnectivity
TI E2E Community Home Page
e2e.ti.com
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2011, Texas Instruments Incorporated
LM3444
Application Note 2097 LM3444 - 230VAC, 8W Isolated Flyback LED Driver
Literature Number: SNVA462E
National Semiconductor
Application Note 2097
Clinton Jensen
LM3444 - 230VAC, 8W
Isolated Flyback LED Driver
May 3, 2011
Introduction
Key Features
This demonstration board highlights the performance of a
LM3444 based Flyback LED driver solution that can be used
to power a single LED string consisting of 4 to 10 series con-
nected LEDs from an 180 VRMS to 265 VRMS, 50 Hz input
power supply. The key performance characteristics under
typical operating conditions are summarized in this applica-
tion note.
•
Line injection circuitry enables PFC values greater than
0.98
•
•
Adjustable LED current and switching frequency
Flicker free operation
Applications
•
•
•
Solid State Lighting
Industrial and Commercial Lighting
Residential Lighting
This is a four-layer board using the bottom and top layer for
component placement. The demonstration board can be
modified to adjust the LED forward current, the number of se-
ries connected LEDs that are driven and the switching fre-
quency. Refer to the LM3444 datasheet for detailed instruc-
tions.
A bill of materials is included that describes the parts used on
this demonstration board. A schematic and layout have also
been included along with measured performance character-
istics.
Performance Specifications
Based on an LED Vf = 3.6V
Symbol
VIN
Parameter
Input voltage
Min
Typ
230 VRMS
21.5 V
Max
180 VRMS
265 VRMS
VOUT
ILED
POUT
fsw
LED string voltage
LED string average current
Output power
13 V
36 V
-
-
-
350 mA
7.5 W
-
-
-
Switching frequency
67 kHz
Demo Board
30139704
© 2011 National Semiconductor Corporation
301397
www.national.com
LM3444 230VAC, 8W Isolated Flyback LED Driver Demo Board Schematic
30139701
Warning:
Warning:
The LM3444 evaluation board has exposed high voltage components that present a shock hazard. Caution must be taken when handling the evaluation
board. Avoid touching the evaluation board and removing any cables while the evaluation board is operating.
The ground connection on the evaluation board is NOT referenced to earth ground. If an oscilloscope ground lead is connected to the evaluation
board ground test point for analysis and the mains AC power is applied (without any isolation), the fuse (F1) will fail open. For bench evaluation, either
the input AC power source or the bench measurement equipment should be isolated from the earth ground connection. Isolating the evaliation board
(using 1:1 line isolation transformer) rather than the oscilloscope is highly recommended.
Warning:
The LM3444 evaluation board should not be powered with an open load. For proper operation, ensure that the desired number of LEDs are connected
at the output before applying power to the evaluation board.
www.national.com
2
LM3444 Device Pin-Out
30139702
Pin Descriptions – 10 Pin MSOP
Pin #
Name
NC
Description
1
2
3
4
No internal connection.
No internal connection.
No internal connection.
NC
NC
COFF
OFF time setting pin. A user set current and capacitor connected from the output to this pin sets the constant OFF
time of the switching controller.
5
6
7
FILTER Filter input. A capacitor tied to this pin filters the error amplifier. Could also be used as an analog dimming input.
GND
ISNS
Circuit ground connection.
LED current sense pin. Connect a resistor from main switching MOSFET source, ISNS to GND to set the maximum
LED current.
8
GATE
Power MOSFET driver pin. This output provides the gate drive for the power switching MOSFET of the buck
controller.
9
VCC
NC
Input voltage pin. This pin provides the power for the internal control circuitry and gate driver.
No internal connection.
10
3
www.national.com
Bill of Materials
Designator
Description
Manufacturer
National
Semiconductor
Part Number
LM3444MM
RoHS
U1
C1
Offline LED Driver, PowerWise
Ceramic, X7R, 250VAC, 10%
Y
Murata Electronics
North America
DE1E3KX332MA5BA01
Y
C2
C3
C4
Ceramic, Polypropylene, 400VDC, 10%
CAP, CERM, 330pF, 630V, +/-5%, C0G/NP0, 1206
Ceramic, X7R, 250V, X2, 10%, 2220
WIMA
TDK
MKP10-.033/400/5P10
C3216C0G2J331J
Y
Y
Y
Murata Electronics
North America
GA355DR7GF472KW01L
C5
C9, C11
C10
CAP, Film, 0.033µF, 630V, +/-10%, TH
EPCOS Inc
MuRata
B32921C3333K
Y
Y
Y
Y
Y
Y
Y
CAP, CERM, 1µF, 50V, +/-10%, X7R, 1210
CAP, CERM, 0.47µF, 50V, +/-10%, X7R, 0805
Aluminium Electrolytic, 680uF, 35V, 20%,
CAP, CERM, 1µF, 35V, +/-10%, X7R, 0805
CAP, CERM, 0.1µF, 25V, +/-10%, X7R, 0603
GRM32RR71H105KA01L
GRM21BR71H474KA88L
UHE1V681MHD6
MuRata
C12
Nichicon
Taiyo Yuden
MuRata
C13
GMK212B7105KG-T
GRM188R71E104KA01D
TPSC476K016R0350
C14
C15
CAP, TANT, 47uF, 16V, +/-10%, 0.35 ohm, 6032-28 AVX
SMD
C18
C20
CAP, CERM, 2200pF, 50V, +/-10%, X7R, 0603
CAP, CERM, 330pF, 50V, +/-5%, C0G/NP0, 0603
DIODE TVS 250V 600W UNI 5% SMD
Diode, Switching-Bridge, 600V, 0.8A, MiniDIP
Diode, Silicon, 1000V, 1A, SOD-123
MuRata
GRM188R71H222KA01D
GRM1885C1H331JA01D
P6SMB250A
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
MuRata
D1
Littelfuse
Diodes Inc.
D2
HD06-T
D3
Comchip Technology CGRM4007-G
STMicroelectronics STPS1H100A
D4
Diode, Schottky, 100V, 1A, SMA
D5, D10
D6
Diode, Zener, 13V, 200mW, SOD-323
Diode, Zener, 36V, 550mW, SMB
Diodes Inc
DDZ13BS-7
ON Semiconductor
1SMB5938BT3G
D7, D8, D9
F1
Diode, Schottky, 100V, 150 mA, SOD-323
Fuse, 500mA, 250V, Time-Lag, SMT
STMicroelectronics BAT46JFILM
Littelfuse Inc
Keystone
0443.500DR
1902C
H1, H2, H5, H6 Standoff, Hex, 0.5"L #4-40 Nylon
H3, H4, H7, H8 Machine Screw, Round, #4-40 x 1/4, Nylon, Philips
panhead
B&F Fastener Supply NY PMS 440 0025 PH
J1, J2
L1, L2
Conn Term Block, 2POS, 5.08mm PCB
Phoenix Contact
TDK Corporation
1715721
Y
Y
Inductor, Radial Lead Inductors, Shielded, 4.7mH,
130mA, 12.20ohm, 7.5mm Radial,
TSL080RA-472JR13-PF
LED+, LED-, Terminal, 22 Gauge Wire, Terminal, 22 Guage Wire 3M
TP7, TP8
923345-02-C
Y
Y
Q1
MOSFET, N-CH, 600V, 200mA, SOT-223
Fairchild
FQT1N60CTF_WS
Semiconductor
Q2
Q3
Transistor, NPN, 300V, 500mA, SOT-23
MOSFET, N-CH, 650V, 800mA, IPAK
Diodes Inc.
MMBTA42-7-F
SPU01N60C3
Y
Y
Infineon
Technologies
R1
R2, R7
R3, R8
R4, R12
R13
RES, 221 ohm, 1%, 0.25W, 1206
RES, 200k ohm, 1%, 0.25W, 1206
RES, 309k ohm, 1%, 0.25W, 1206
RES, 10k ohm, 5%, 0.25W, 1206
RES, 33.0 ohm, 1%, 0.25W, 1206
RES, 10 ohm, 5%, 0.125W, 0805
RES, 10.0k ohm, 1%, 0.1W, 0603
RES, 10 ohm, 5%, 0.1W, 0603
RES, 1.91k ohm, 1%, 0.1W, 0603
RES, 2.70 ohm, 1%, 0.25W, 1206
Vishay-Dale
Vishay-Dale
Vishay-Dale
Vishay-Dale
Vishay-Dale
Vishay-Dale
Vishay-Dale
Vishay-Dale
Vishay-Dale
Panasonic
CRCW1206221RFKEA
CRCW1206200KFKEA
CRCW1206309KFKEA
CRCW120610K0JNEA
CRCW120633R0FKEA
CRCW080510R0JNEA
CRCW060310K0FKEA
CRCW060310R0JNEA
CRCW06031K91FKEA
ERJ-8RQF2R7V
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
R14
R15
R19
R20
R21
www.national.com
4
Designator
R22
Description
Manufacturer
Vishay-Dale
Part Number
CRCW080510R7FKEA
CRCW0603324KFKEA
MF72-060D5
RoHS
RES, 10.7 ohm, 1%, 0.125W, 0805
RES, 324k ohm, 1%, 0.1W, 0603
Y
Y
Y
Y
Y
Y
R23
Vishay-Dale
Cantherm
RT1
Current Limitor Inrush, 60Ohm, 20%, 5mm Raidal
FLBK TFR, 2.07 mH, Np=140T, Ns=26T, Na= 20T
Terminal, Turret, TH, Double
T1
Wurth Elektornik
750815040 REV 1
TP9, TP10
VR1
Keystone Electronics 1502-2
EPCOS Inc S10K275E2
Varistor 275V 55J 10mm DISC
5
www.national.com
Transformer Design
Mfg: Wurth Electronics, Part #: 750815040 Rev. 01
30139709
Parameter
Test Conditions
20°C
Value
D.C. Resistance (3-1)
D.C. Resistance (6-4)
D.C. Resistance (10-13)
Inductance (3-1)
1.91 Ω ± 10%
0.36 Ω ± 10%
20°C
20°C
0.12 Ω ± 10%
10 kHz, 100 mVAC
10 kHz, 100 mVAC
10 kHz, 100 mVAC
2.12 mH ± 10%
46.50 µH ± 10%
74.00 µH ± 10%
18.0 µH Typ., 22.60 µH Max.
4500 VAC, 1 minute
7:1 ± 1%
Inductance (6-4)
Inductance (10-13)
Leakage Inductance (3-1)
Dielectric (1-13)
Turns Ratio
100 kHz, 100 mAVAC (tie 6+4, 10+13)
tie (3+4), 4500 VAC, 1 second
(3-1):(6-4)
Turns Ratio
(3-1):(10:13)
5.384:1 ± 1%
www.national.com
6
Demo Board Wiring Overview
30139703
Wiring Connection Diagram
Test Point
Name
I/O
Description
LED Constant Current Supply
TP10, J2-1
LED +
Output
Supplies voltage and constant-current to anode of LED string.
TP9, J2-2
J1-1
LED -
LINE
Output
Input
LED Return Connection (not GND)
Connects to cathode of LED string. Do NOT connect to GND.
AC Line Voltage
Connects directly to AC line of a 230VAC system.
J1-2
NEUTRAL
Input
AC Neutral
Connects directly to AC neutral of a 230VAC system.
Demo Board Assembly
30139705
Top View
30139706
Bottom View
7
www.national.com
Typical Performance Characteristics (Note 1, Note 2, Note 3)
Efficiency vs. Line Voltage
Original Circuit
Efficiency vs. Line Voltage
Modified Circuits
0.97
0.93
0.89
0.85
0.81
0.77
0.73
0.68
0.64
0.60
Mod C (10 LEDs)
10 LEDs
8 LEDs
0.87
0.85
0.82
0.80
0.78
Mod B (8 LEDs)
6 LEDs
4 LEDs
Original (6 LEDs)
Mod A (4 LEDs)
180 190 200 210 220 230 240 250 260
INPUT VOLTAGE (V
180 190 200 210 220 230 240 250 260
INPUT VOLTAGE (V
)
)
RMS
RMS
30139710
30139714
LED Current vs. Line Voltage
Original Circuit
LED Current vs. Line Voltage
Modified Circuits
650
550
450
350
250
150
50
600
550
500
450
400
350
300
250
200
150
100
Mod C (10 LEDs)
Mod B (8 LEDs)
4 LEDs
6 LEDs
Original (6 LEDs)
Mod A (4 LEDs)
8 LEDs
10 LEDs
180 190 200 210 220 230 240 250 260
INPUT VOLTAGE (V
180 190 200 210 220 230 240 250 260
INPUT VOLTAGE (V
)
)
RMS
RMS
30139711
30139715
www.national.com
8
Power Factor vs. Line Voltage
Output Power vs. Line Voltage
Original Circuit
1.000
0.995
0.990
0.985
0.980
0.975
0.970
0.965
0.960
0.955
0.950
12
11
10
9
10 LEDs
8 LEDs
4 LEDs
8
7
6 LEDs
6
5
4
3
2
180 190 200 210 220 230 240 250 260
180 190 200 210 220 230 240 250 260
LINE VOLTAGE (V
)
RMS
INPUT VOLTAGE (V
)
RMS
30139713
30139712
Output Power vs. Line Voltage
Modified Circuits
Line Voltage and Line Current
(VIN = 230VRMS, 6 LEDs, ILED = 350mA)
25.0
22.5
20.0
17.5
Mod B (8 LEDs)
15.0 Mod C (10 LEDs)
12.5
10.0
7.5
5.0
2.5
Mod A (4 LEDs)
Original (6 LEDs)
0.0
Ch1: Line Voltage (100 V/div); Ch3: Line C3u01r3r9e71n8t
(20 mA/div); Time (4 ms/div)
180 190 200 210 220 230 240 250 260
INPUT VOLTAGE (V
RMS
)
30139717
Output Voltage and LED Current
(VIN = 230VRMS, 6 LEDs, ILED = 350mA)
Power MOSFET Drain and ISNS (Pin-7) Voltage
(VIN = 230VRMS, 6 LEDs, ILED = 350mA)
30139720
30139721
Ch1: Output Voltage (10 V/div); Ch3: LED Current
(100 mA/div); Time (4 ms/div)
Ch1: Drain Voltage (100V/div); Ch4: ISNS Voltage
(500 mV/div); Time (4 µs/div)
9
www.national.com
FILTER (Pin-5) and ISNS (Pin-7) Voltage
(VIN=230VRMS, 6 LEDs, ILED = 350mA
30139722
Ch1: FILTER Voltage (200 mV/div); ISNS Voltage
(200 mV/div); Time (4 µs/div)
Note 1: Original Circuit (6 LEDs operating at 350mA): R21 = 2.7Ω; Modification A (10 LEDs operating at 375mA): R21 = 1.8Ω; Modification B (8 LEDs operating
at 350mA): R21 = 2.2Ω; Modification C (4 LEDs operating at 315mA): R21 = 3.9Ω
Note 2: The output power can be varied to achieve desired LED current by interpolating R21 values between the maximum of 3.9 Ω and minimum of 1.8 Ω
Note 3: The maximum output voltage is clamped to 36 V. For operating LED string voltage > 36 V, replace D6 with suitable alternative
PCB Layout
30139707
Top Layer
www.national.com
10
30139740
Top Middle Layer
30139741
Bottom Middle Layer
11
www.national.com
30139708
Bottom Layer
www.national.com
12
mA. The 100 Hz current ripple flowing through the LED string
was measured to be 194 mApk-pk at full load. The magnitude
of the ripple is a function of the value of energy storage ca-
pacitors connected across the output. The ripple current can
be reduced by increasing the value of energy storage capac-
itor or by increasing the LED string voltage.
Experimental Results
The LED driver is designed to accurately emulate an incan-
descent light bulb and therefore behave as an emulated
resistor. The resistor value is determined based on the LED
string configuration and the desired output power. The circuit
then operates in open-loop, with a fixed duty cycle based on
a constant on-time and constant off-time that is set by select-
ing appropriate circuit components.
The LED driver switching frequency is measured to be close
to the specified 67 kHz. The circuit operates with a constant
duty cycle of 0.21 and consumes near 9W of input power. The
driver steady state performance for an LED string consisting
of 6 series LEDs is summarized in the following table.
PERFORMANCE
In steady state, the LED string voltage is measured to be
21.55 V and the average LED current is measured as 347.5
MEASURED EFFICIENCY AND LINE REGULATION (6 LEDS)
PIN(W) VOUT (V) ILED (mA) POUT (W)
5.42 20.59 219.40 4.52
VIN (VRMS
180
)
IIN (mARMS
30.65
)
Efficiency (%) Power Factor
83.3
83.3
83.2
83.2
83.3
83.6
83.6
83.5
83.3
0.9867
0.9869
0.9870
0.9871
0.9872
0.9873
0.9874
0.9875
0.9877
190
32.35
6.06
6.75
7.47
8.20
8.96
9.76
10.62
11.57
20.80
21.00
21.18
21.37
21.55
21.72
21.90
22.07
242.55
267.37
293.39
320.18
347.51
375.52
404.82
436.75
5.05
5.62
6.21
6.84
7.49
8.15
8.86
9.64
200
34.21
210
36.01
220
37.74
230
39.44
240
41.22
250
43..29
45.06
260
CURRENT THD
the fundamental current (as shown in the following table) and
therefore meets the requirements of the IEC 61000-3-2
Class-3 standard. Total harmonic distortion was measured to
be less than 1.2%.
The LED driver is able to achieve close to unity power factor
(PF ~ 0.98) which meets Energy Star requirements. This de-
sign also exhibits low current harmonics as a percentage of
MEASURED HARMONIC CURRENT
Harmonic
Class C Limit (mA)
Measured (mA)
0.022
0.125
0.11
2
0.78
11.61
3.90
2.73
1.95
1.73
1.73
1.73
1.73
1.73
1.73
1.73
1.73
1.73
1.73
1.73
3
5
7
0.105
0.11
9
11
13
15
17
19
21
23
25
27
29
31
0.15
0.093
0.071
0.154
0.165
0.065
0.065
0.08
0.084
0.065
0.07
13
www.national.com
Electromagnetic Interference (EMI)
The EMI input filter of this evaluation board is configured as
shown in the following circuit diagram.
30139731
FIGURE 1. Input EMI Filter and Rectifier Circuit
In order to get a quick estimate of the EMI filter performance,
only the PEAK conductive EMI scan was measured and the
data was compared to the Class B conducted EMI limits pub-
lished in FCC – 47, section 15.(Note 4)
30139732
FIGURE 2. Peak Conductive EMI scan per CISPR-22, Class B Limits
Note 4: CISPR 15 compliance pending
www.national.com
14
ILED = 348 mA
Thermal Analysis
The board temperature was measured using an IR camera
(HIS-3000, Wahl) while running under the following condi-
tions:
# of LEDs = 6
POUT = 7.2 W
The results are shown in the following figures.
VIN = 230 VRMS
30139733
FIGURE 3. Top Side Thermal Scan
30139734
FIGURE 4. Bottom Side Thermal Scan
15
www.national.com
TER pin, the on-time can be made to be constant. With a DCM
Flyback, Δi needs to increase as the input voltage line in-
creases. Therefore a constant on-time (since inductor L is
constant) can be obtained.
Circuit Analysis and Explanations
INJECTING LINE VOLTAGE INTO FILTER (ACHIEVING
PFC > 0.98)
By using the line voltage injection technique, the FILTER pin
has the voltage wave shape shown in Figure 6 on it. Voltage
at VFILTER peak should be kept below 1.25V. At 1.25V current
limit is tripped. C11 is small enough not to distort the AC signal
but adds a little filtering.
If a small portion (750mV to 1.00V) of line voltage is injected
at FILTER of the LM3444, the circuit is essentially turned into
a constant power flyback as shown in Figure 5.
Although the on-time is probably never truly constant, it can
be observed in Figure 7 how (by adding the rectified voltage)
the on-time is adjusted.
30139737
FIGURE 6. FILTER Waveform
For this evaluation board, the following resistor values are
used:
R3 = R8 = 309 kΩ
R20 = 1.91 kΩ
Therefore the voltages observed on the FILTER pin will be as
follows for listed input voltages:
For VIN = 180VRMS, VFILTER, Pk = 0.78V
For VIN = 230VRMS, VFILTER, Pk = 1.00V
For VIN = 265VRMS, VFILTER, Pk = 1.15V
30139735
FIGURE 5. Line Voltage Injection Circuit
Using this technique, a power factor greater than 0.98 can be
achieved without additional passive active power factor con-
trol (PFC) circuitry.
The LM3444 works as a constant off-time controller normally,
but by injecting the 1.0VPk rectified AC voltage into the FIL-
30139736
FIGURE 7. Typical Operation of FILTER Pin
www.national.com
16
Notes
17
www.national.com
Notes
For more National Semiconductor product information and proven design tools, visit the following Web sites at:
www.national.com
Products
www.national.com/amplifiers
Design Support
www.national.com/webench
Amplifiers
WEBENCH® Tools
App Notes
Audio
www.national.com/audio
www.national.com/timing
www.national.com/adc
www.national.com/interface
www.national.com/lvds
www.national.com/power
www.national.com/appnotes
www.national.com/refdesigns
www.national.com/samples
www.national.com/evalboards
www.national.com/packaging
www.national.com/quality/green
www.national.com/contacts
www.national.com/quality
www.national.com/feedback
www.national.com/easy
Clock and Timing
Data Converters
Interface
Reference Designs
Samples
Eval Boards
LVDS
Packaging
Power Management
Green Compliance
Distributors
Switching Regulators www.national.com/switchers
LDOs
www.national.com/ldo
www.national.com/led
www.national.com/vref
www.national.com/powerwise
Quality and Reliability
Feedback/Support
Design Made Easy
Applications & Markets
Mil/Aero
LED Lighting
Voltage References
PowerWise® Solutions
www.national.com/solutions
www.national.com/milaero
www.national.com/solarmagic
www.national.com/training
Serial Digital Interface (SDI) www.national.com/sdi
Temperature Sensors
PLL/VCO
www.national.com/tempsensors SolarMagic™
www.national.com/wireless
PowerWise® Design
University
THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION
(“NATIONAL”) PRODUCTS. NATIONAL MAKES NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY
OR COMPLETENESS OF THE CONTENTS OF THIS PUBLICATION AND RESERVES THE RIGHT TO MAKE CHANGES TO
SPECIFICATIONS AND PRODUCT DESCRIPTIONS AT ANY TIME WITHOUT NOTICE. NO LICENSE, WHETHER EXPRESS,
IMPLIED, ARISING BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL PROPERTY RIGHTS IS GRANTED BY THIS
DOCUMENT.
TESTING AND OTHER QUALITY CONTROLS ARE USED TO THE EXTENT NATIONAL DEEMS NECESSARY TO SUPPORT
NATIONAL’S PRODUCT WARRANTY. EXCEPT WHERE MANDATED BY GOVERNMENT REQUIREMENTS, TESTING OF ALL
PARAMETERS OF EACH PRODUCT IS NOT NECESSARILY PERFORMED. NATIONAL ASSUMES NO LIABILITY FOR
APPLICATIONS ASSISTANCE OR BUYER PRODUCT DESIGN. BUYERS ARE RESPONSIBLE FOR THEIR PRODUCTS AND
APPLICATIONS USING NATIONAL COMPONENTS. PRIOR TO USING OR DISTRIBUTING ANY PRODUCTS THAT INCLUDE
NATIONAL COMPONENTS, BUYERS SHOULD PROVIDE ADEQUATE DESIGN, TESTING AND OPERATING SAFEGUARDS.
EXCEPT AS PROVIDED IN NATIONAL’S TERMS AND CONDITIONS OF SALE FOR SUCH PRODUCTS, NATIONAL ASSUMES NO
LIABILITY WHATSOEVER, AND NATIONAL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY RELATING TO THE SALE
AND/OR USE OF NATIONAL PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR
PURPOSE, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY
RIGHT.
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR
SYSTEMS WITHOUT THE EXPRESS PRIOR WRITTEN APPROVAL OF THE CHIEF EXECUTIVE OFFICER AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
Life support devices or systems are devices which (a) are intended for surgical implant into the body, or (b) support or sustain life and
whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected
to result in a significant injury to the user. A critical component is any component in a life support device or system whose failure to perform
can be reasonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness.
National Semiconductor and the National Semiconductor logo are registered trademarks of National Semiconductor Corporation. All other
brand or product names may be trademarks or registered trademarks of their respective holders.
Copyright© 2011 National Semiconductor Corporation
For the most current product information visit us at www.national.com
National Semiconductor
Americas Technical
Support Center
National Semiconductor Europe
Technical Support Center
Email: europe.support@nsc.com
National Semiconductor Asia
Pacific Technical Support Center
Email: ap.support@nsc.com
National Semiconductor Japan
Technical Support Center
Email: jpn.feedback@nsc.com
Email: support@nsc.com
Tel: 1-800-272-9959
www.national.com
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements,
and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should
obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are
sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard
warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where
mandated by government requirements, testing of all parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and
applications using TI components. To minimize the risks associated with customer products and applications, customers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right,
or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information
published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a
warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual
property of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied
by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive
business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional
restrictions.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all
express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not
responsible or liable for any such statements.
TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably
be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing
such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products
and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be
provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in
such safety-critical applications.
TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are
specifically designated by TI as military-grade or "enhanced plastic." Only products designated by TI as military-grade meet military
specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at
the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use.
TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are
designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated
products in automotive applications, TI will not be responsible for any failure to meet such requirements.
Following are URLs where you can obtain information on other Texas Instruments products and application solutions:
Products
Audio
Applications
www.ti.com/audio
amplifier.ti.com
dataconverter.ti.com
www.dlp.com
Communications and Telecom www.ti.com/communications
Amplifiers
Data Converters
DLP® Products
DSP
Computers and Peripherals
Consumer Electronics
Energy and Lighting
Industrial
www.ti.com/computers
www.ti.com/consumer-apps
www.ti.com/energy
dsp.ti.com
www.ti.com/industrial
www.ti.com/medical
www.ti.com/security
Clocks and Timers
Interface
www.ti.com/clocks
interface.ti.com
logic.ti.com
Medical
Security
Logic
Space, Avionics and Defense www.ti.com/space-avionics-defense
Transportation and Automotive www.ti.com/automotive
Power Mgmt
Microcontrollers
RFID
power.ti.com
microcontroller.ti.com
www.ti-rfid.com
Video and Imaging
www.ti.com/video
OMAP Mobile Processors www.ti.com/omap
Wireless Connectivity www.ti.com/wirelessconnectivity
TI E2E Community Home Page
e2e.ti.com
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2011, Texas Instruments Incorporated
LM3444
Application Note 2083 LM3444 A19 Edison Retrofit Evaluation Board
Literature Number: SNVA455B
National Semiconductor
Application Note 2083
Clinton Jensen
LM3444 A19 Edison Retrofit
Evaluation Board
December 2, 2010
input voltage are valid only for the demonstration board as
shipped with the schematic below. Please refer to the LM3444
data sheet for detailed information regarding the LM3444 de-
vice. The board is currently set up to drive five to thirteen
series connected LEDs, but the evaluation board may be
modified to accept more series LEDs. Refer to the tables in
this document for modifying the board to accept more LEDs
and/or adjust for different current levels.
Introduction
The evaluation board included in this shipment converts
85VAC to 135VAC input and drives five to thirteen series con-
nected LED’s at the currents listed in the Evaluation Board
Operating Conditions section. This is a two-layer board using
the bottom and top layer for component placement. The board
is surrounded by a larger area allowing for extra test points
and connectors for ease of evaluation. The actual board size
is contained inside the larger outer area and can be cut out
for the smallest size possible. The evaluation board can be
modified to adjust the LED forward current and the number of
series connected LEDs. The topology used for this evaluation
board eliminates the need for passive power factor correction
and results in high efficiency and power factor with minimal
component count which results in a size that can fit in a stan-
dard A19 Edison socket. Output current is regulated within
±15% of nominal from circuit to circuit and over line voltage
variation. Refer to the LM3444 datasheet for details on the
LM3444 IC.
Evalution Board Operating
Conditions
VIN = 85VAC to 135VAC
5 to 13 series connected LEDs as configured with the currents
listed below
Can drive up to 18 series LEDs (see table)
ILED = 340 mA (5 LEDs)
ILED = 300 mA (7 LEDs)
ILED = 260 mA (9 LEDs)
A bill of materials below describes the parts used on this
demonstration board. A schematic and layout have also been
included below along with measured performance character-
istics including EMI/EMC data. The above restrictions for the
ILED = 230 mA (11 LEDs)
ILED = 205 mA (13 LEDs)
Simplified LM3444 Schematic
30131201
Warning:
Warning:
The LM3444 evaluation boards have no isolation or any type of protection from shock. Caution must be taken when handling evaluation board.
Avoid touching evaluation board, and removing any cables while evaluation board is operating. Isolating the evaluation board rather than the
oscilloscope is highly recommended.
This LM3444 evaluation PCB is a non-isolated design. The ground connection on the evaluation board is NOT referenced to earth ground. If an
oscilloscope ground lead is connected to the evaluation board ground test point for analysis, and AC power is applied, the fuse (F1) will fail open.
The oscilloscope should be powered via an isolation transformer before an oscilloscope ground lead is connected to the evaluation board.
© 2010 National Semiconductor Corporation
301312
www.national.com
Pin-Out
30131203
10-Pin MSOP
Pin Description 10 Pin MSOP
Pin #
Name
Description
1
2
3
4
NC
NC
No internal connection.
No internal connection.
No internal connection.
NC
COFF
OFF time setting pin. A user set current and capacitor connected from the output to this pin sets the constant
OFF time of the switching controller.
5
FILTER
Filter input. A capacitor tied to this pin filters the error amplifier. Could also be used as an analog dimming
input.
6
7
GND
ISNS
Circuit ground connection.
LED current sense pin. Connect a resistor from main switching MOSFET source, ISNS to GND to set the
maximum LED current.
8
GATE
Power MOSFET driver pin. This output provides the gate drive for the power switching MOSFET of the buck
controller.
9
VCC
NC
Input voltage pin. This pin provides the power for the internal control circuitry and gate driver.
No internal connection.
10
www.national.com
2
30131207
A N - 2 0 8
Bill of Materials LM3444 Evaluation Board
REF DES
Description
IC DRIVER LED 10MSOP
MFG
MFG Part Number
LM3444MM
U1
National Semiconductor
Johanson Dielectrics
Vishay/BC Components
Nichicon
C1, C10
Ceramic, 47000pF, 500V, X7R, 1210
CAP FILM MKP .0047µF 310VAC X2
CAP 470µF 50V ELECT PW RADIAL
DNP
501S41W473KV4E
BFC233820472
UPW1H471MHD
C2
C3
C4/RBLDR (Note 1)
C5
Ceramic, .33µF, 250V, X7R, 1812
CAP .10µF 305VAC EMI SUPPRESSION
Ceramic, 47µF, X5R, 16V, 1210
Ceramic, 470pF, 50V, X7R, 0603
Ceramic, 0.1µF, 16V, X7R, 0603
Ceramic, 0.47µF, 16V, X7R, 0603
DIODE SCHOTTKY 1A 200V PWRDI 123
Bridge Rectifier, Vr = 400V, Io = 0.8A, Vf = 1V
DIODE FAST 1A 300V SMA
TDK Corporation
EPCOS
C4532X7R2E334K
B32921C3104M
GRM32ER61C476ME15L
GRM188R71H471KA01D
GRM188R71C104KA01D
GRM188R71C474KA88D
DFLS1200-7
C6
C8
MuRata
C12
MuRata
C15
MuRata
C14
MuRata
D1
Diodes Inc.
D2
Diodes Inc.
HD04-T
D4
Fairchild Semi conductor
Fairchild Semi conductor
Diodes Inc.
ES1F
D7
DIODE ZENER 15V 500MW SOD-123
DIODE SCHOTTKY 1A 200V PWRDI 123
FUSE 1A 125V FAST
MMSZ5245B
D8
DFLS1200-7
F1
Cooper/Bussman
Tyco Electronics
J.W. Miller/Bourns
Coilcraft Inc.
3M
6125FA1A
J5, J10
CONN HEADER .312 VERT 2POS TIN
INDUCTOR 3900µH .12A RADIAL
820µH, Shielded Drum Core
1-1318301-2
L1, L2
RL875S-392K-RC
MSS1038-824KL
923345-03-C
L3
M1
JUMPER WIRE 0.3" J6 TO J1
JUMPER WIRE 0.3" J7 to J4
JUMPER WIRE 0.3" J2 TO J8
JUMPER WIRE 0.3" J3 TO J9
MOSFET N-CH 240V 260MA SOT-89
MOSFET N-CH 250V 4.4A DPAK
RES 200kΩ, 0.25W, 1%, 1206
RES 274kΩ, 0.25W, 1%, 1206
RES 430Ω, 1/2W, 5%, 2010
M2
3M
923345-03-C
M3
3M
923345-03-C
M4
3M
923345-03-C
Q1
Infineon Technologies
Fairchild Semi conductor
Vishay-Dale
Vishay-Dale
Vishay-Dale
Vishay-Dale
BSS87 L6327
Q2
FDD6N25TM
R1, R3
CRCW1206200kFKEA
CRCW1206274kFKEA
CRCW2010430RJNEF
CRCW120630k1FKEA
R2, R7
R4
R6, R24
RES 30.1kΩ, 0.25W, 1%, 1206
DNP
R10
R12
Vishay-Dale
Vishay-Dale
CRCW06034R70JNEA
CRCW12083R54FNEA
CRCW06033K16FKEA
CRCW0603255KFKEA
CRCW080540R2FKEA
MF72-060D5
RES 4.7Ω, 0.1W, 5%, 0603
R14
RES 1.54Ω, 1/4W, 1%, 1206
RES 3.16kΩ, 0.1w, 1%, 0603
RES 255kΩ, 0.1W, 1%, 0603
RES 40.2Ω, 0.125W, 1%, 0805
CURRENT LIMITOR INRUSH 60Ω 20%
Terminal, Turret, TH, Double
R15
Vishay-Dale
R16
Vishay-Dale
R22
RT1
Vishay-Dale
Cantherm
TP1, TP2, TP3, TP4
Keystone Electronics
1502-2
Note 1: C4/RBLDR is a dual purpose pad which is unpopulated by default. A ceramic capacitor (C4) may be used here if extra high frequency bypassing is desired
across the LED load. Alternatively a bleeder resistor (RBLDR) in the range of 10kΩ to 100kΩ may be placed here to quickly discharge C3 and prevent prolonged
LED glow due to the energy stored in C3.
www.national.com
4
Output Current versus Number of LEDs for Various Modifications
# of LEDs
Output Current (mA)
Original Circuit
Output Current (mA)
Modification A (Note 2)
Output Current (mA)
Modification B (Note 3)
Output Current (mA)
Modification C (Note 4)
2
520
500
475
455
432
412
3
4
5
340
315
300
275
260
245
230
215
205
196
190
183
175
170
248
235
222
210
200
190
180
170
164
156
150
142
135
130
265
250
237
224
212
200
190
180
170
162
155
148
142
137
6
7
8
9
10
11
12
13
14 (Note 5)
15 (Note 5)
16 (Note 5)
17 (Note 5)
18 (Note 5)
Note 2: Modification A: R14 = 2.37Ω, R16 = 150kΩ, C3 = 330µF, 63V.
Note 3: Modification B: R14 = 2.2Ω, R16 = 165kΩ.
Note 4: Modification C: R14 = 1.2Ω, R16 = 137kΩ, L3 = 470µH, C3 = 1000µF, 25V.
Note 5: For all applications using greater than 13 LEDs a 330µF, 63V output capacitor (C3) was used.
5
www.national.com
Typical Performance Characteristics
Efficiency vs. Line Voltage
Original Circuit
Power Factor vs. Line Voltage
Original Circuit
30131202
30131204
Efficiency vs. Line Voltage
Modification A
Power Factor vs. Line Voltage
Modification A
30131211
30131212
Efficiency vs. Line Voltage
Modification B
Power Factor vs. Line Voltage
Modification B
30131213
30131214
www.national.com
6
PCB Layout
30131210
Top Layer
30131209
Bottom Layer
Warning:
The LM3444 evaluation boards have no isolation or any type of protection from shock. Caution must be taken when handling evaluation board. Avoid
touching evaluation board, and removing any cables while evaluation board is operating. Isolating the evaluation board rather than the oscilloscope
is highly recommended.
7
www.national.com
EMI/EMC Information
30131215
Radiated EMI
30131216
Conducted EMC. Line = Blue, Neutral = Black.
Frequency
Quasi-peak
Amplitude
Quasi-peak
Limit
Quasi-peak
Delta
Average
Amplitude
Average Limit
Average
Delta
Neutral
Line
154 kHz
1.1 MHz
57
66
-9
47
31
56
46
-9
-15
www.national.com
8
Notes
9
www.national.com
Notes
For more National Semiconductor product information and proven design tools, visit the following Web sites at:
www.national.com
Products
www.national.com/amplifiers
Design Support
www.national.com/webench
Amplifiers
WEBENCH® Tools
App Notes
Audio
www.national.com/audio
www.national.com/timing
www.national.com/adc
www.national.com/interface
www.national.com/lvds
www.national.com/power
www.national.com/appnotes
www.national.com/refdesigns
www.national.com/samples
www.national.com/evalboards
www.national.com/packaging
www.national.com/quality/green
www.national.com/contacts
www.national.com/quality
www.national.com/feedback
www.national.com/easy
Clock and Timing
Data Converters
Interface
Reference Designs
Samples
Eval Boards
LVDS
Packaging
Power Management
Green Compliance
Distributors
Switching Regulators www.national.com/switchers
LDOs
www.national.com/ldo
www.national.com/led
www.national.com/vref
www.national.com/powerwise
Quality and Reliability
Feedback/Support
Design Made Easy
Applications & Markets
Mil/Aero
LED Lighting
Voltage References
PowerWise® Solutions
www.national.com/solutions
www.national.com/milaero
www.national.com/solarmagic
www.national.com/training
Serial Digital Interface (SDI) www.national.com/sdi
Temperature Sensors
PLL/VCO
www.national.com/tempsensors SolarMagic™
www.national.com/wireless
PowerWise® Design
University
THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION
(“NATIONAL”) PRODUCTS. NATIONAL MAKES NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY
OR COMPLETENESS OF THE CONTENTS OF THIS PUBLICATION AND RESERVES THE RIGHT TO MAKE CHANGES TO
SPECIFICATIONS AND PRODUCT DESCRIPTIONS AT ANY TIME WITHOUT NOTICE. NO LICENSE, WHETHER EXPRESS,
IMPLIED, ARISING BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL PROPERTY RIGHTS IS GRANTED BY THIS
DOCUMENT.
TESTING AND OTHER QUALITY CONTROLS ARE USED TO THE EXTENT NATIONAL DEEMS NECESSARY TO SUPPORT
NATIONAL’S PRODUCT WARRANTY. EXCEPT WHERE MANDATED BY GOVERNMENT REQUIREMENTS, TESTING OF ALL
PARAMETERS OF EACH PRODUCT IS NOT NECESSARILY PERFORMED. NATIONAL ASSUMES NO LIABILITY FOR
APPLICATIONS ASSISTANCE OR BUYER PRODUCT DESIGN. BUYERS ARE RESPONSIBLE FOR THEIR PRODUCTS AND
APPLICATIONS USING NATIONAL COMPONENTS. PRIOR TO USING OR DISTRIBUTING ANY PRODUCTS THAT INCLUDE
NATIONAL COMPONENTS, BUYERS SHOULD PROVIDE ADEQUATE DESIGN, TESTING AND OPERATING SAFEGUARDS.
EXCEPT AS PROVIDED IN NATIONAL’S TERMS AND CONDITIONS OF SALE FOR SUCH PRODUCTS, NATIONAL ASSUMES NO
LIABILITY WHATSOEVER, AND NATIONAL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY RELATING TO THE SALE
AND/OR USE OF NATIONAL PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR
PURPOSE, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY
RIGHT.
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR
SYSTEMS WITHOUT THE EXPRESS PRIOR WRITTEN APPROVAL OF THE CHIEF EXECUTIVE OFFICER AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
Life support devices or systems are devices which (a) are intended for surgical implant into the body, or (b) support or sustain life and
whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected
to result in a significant injury to the user. A critical component is any component in a life support device or system whose failure to perform
can be reasonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness.
National Semiconductor and the National Semiconductor logo are registered trademarks of National Semiconductor Corporation. All other
brand or product names may be trademarks or registered trademarks of their respective holders.
Copyright© 2010 National Semiconductor Corporation
For the most current product information visit us at www.national.com
National Semiconductor
Americas Technical
Support Center
National Semiconductor Europe
Technical Support Center
Email: europe.support@nsc.com
National Semiconductor Asia
Pacific Technical Support Center
Email: ap.support@nsc.com
National Semiconductor Japan
Technical Support Center
Email: jpn.feedback@nsc.com
Email: support@nsc.com
Tel: 1-800-272-9959
www.national.com
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements,
and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should
obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are
sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard
warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where
mandated by government requirements, testing of all parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and
applications using TI components. To minimize the risks associated with customer products and applications, customers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right,
or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information
published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a
warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual
property of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied
by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive
business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional
restrictions.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all
express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not
responsible or liable for any such statements.
TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably
be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing
such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products
and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be
provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in
such safety-critical applications.
TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are
specifically designated by TI as military-grade or "enhanced plastic." Only products designated by TI as military-grade meet military
specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at
the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use.
TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are
designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated
products in automotive applications, TI will not be responsible for any failure to meet such requirements.
Following are URLs where you can obtain information on other Texas Instruments products and application solutions:
Products
Audio
Applications
www.ti.com/audio
amplifier.ti.com
dataconverter.ti.com
www.dlp.com
Communications and Telecom www.ti.com/communications
Amplifiers
Data Converters
DLP® Products
DSP
Computers and Peripherals
Consumer Electronics
Energy and Lighting
Industrial
www.ti.com/computers
www.ti.com/consumer-apps
www.ti.com/energy
dsp.ti.com
www.ti.com/industrial
www.ti.com/medical
www.ti.com/security
Clocks and Timers
Interface
www.ti.com/clocks
interface.ti.com
logic.ti.com
Medical
Security
Logic
Space, Avionics and Defense www.ti.com/space-avionics-defense
Transportation and Automotive www.ti.com/automotive
Power Mgmt
Microcontrollers
RFID
power.ti.com
microcontroller.ti.com
www.ti-rfid.com
Video and Imaging
www.ti.com/video
OMAP Mobile Processors www.ti.com/omap
Wireless Connectivity www.ti.com/wirelessconnectivity
TI E2E Community Home Page
e2e.ti.com
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2011, Texas Instruments Incorporated
LM3444
Application Note 2082 LM3444 -120VAC, 8W Isolated Flyback LED Driver
Literature Number: SNVA454D
National Semiconductor
Application Note 2082
Clinton Jensen
LM3444 -120VAC, 8W
Isolated Flyback LED Driver
December 7, 2010
Introduction
Key Features
This demonstration board highlights the performance of a
LM3444 based Flyback LED driver solution that can be used
to power a single LED string consisting of 4 to 8 series con-
nected LEDs from an 90 VRMS to 135 VRMS, 60 Hz input power
supply. The key performance characteristics under typical
operating conditions are summarized in this application note.
•
Line injection circuitry enables PFC values greater than
0.99
•
•
Adjustable LED current and switching frequency
Flicker free operation
Applications
This is a two-layer board using the bottom and top layer for
component placement. The demonstration board can be
modified to adjust the LED forward current, the number of se-
ries connected LEDs that are driven and the switching fre-
quency. Refer to the LM3444 datasheet for detailed instruc-
tions.
•
•
•
Solid State Lighting
Industrial and Commercial Lighting
Residential Lighting
A bill of materials is included that describes the parts used on
this demonstration board. A schematic and layout have also
been included along with measured performance character-
istics.
Performance Specifications
Based on an LED Vf = 3.57V
Symbol
VIN
Parameter
Input voltage
Min
Typ
120 VRMS
21.4 V
Max
90 VRMS
135 VRMS
VOUT
ILED
POUT
fsw
LED string voltage
LED string average current
Output power
12 V
30 V
-
-
-
350 mA
7.6 W
-
-
-
Switching frequency
79 kHz
Demo Board
30131168
© 2010 National Semiconductor Corporation
301311
www.national.com
LM3444 120VAC, 8W Isolated Flyback LED Driver Demo Board Schematic
30131101
Warning:
Warning:
Warning:
The LM3444 evaluation board has exposed high voltage components that present a shock hazard. Caution must be taken when handling the evaluation
board. Avoid touching the evaluation board and removing any cables while the evaluation board is operating. Isolating the evaluation board rather
than the oscilloscope is highly recommended.
The ground connection on the evaluation board is NOT referenced to earth ground. If an oscilloscope ground lead is connected to the evaluation
board ground test point for analysis and AC power is applied, the fuse (F1) will fail open. The oscilloscope should be powered via an isolation
transformer before an oscilloscope ground lead is connected to the evaluation board.
The LM3444 evaluation board should not be powered with an open load. For proper operation, ensure that the desired number of LEDs are connected
at the output before applying power to the evaluation board.
www.national.com
2
LM3444 Device Pin-Out
30131102
Pin Description 10 Pin MSOP
Pin #
Name
NC
Description
1
2
3
4
No internal connection.
No internal connection.
No internal connection.
NC
NC
COFF
OFF time setting pin. A user set current and capacitor connected from the output to this pin sets the constant OFF
time of the switching controller.
5
6
7
FILTER Filter input. A capacitor tied to this pin filters the error amplifier. Could also be used as an analog dimming input.
GND
ISNS
Circuit ground connection.
LED current sense pin. Connect a resistor from main switching MOSFET source, ISNS to GND to set the maximum
LED current.
8
GATE
Power MOSFET driver pin. This output provides the gate drive for the power switching MOSFET of the buck
controller.
9
VCC
NC
Input voltage pin. This pin provides the power for the internal control circuitry and gate driver.
No internal connection.
10
3
www.national.com
Bill of Materials
Designator
Description
Manufacturer
Part Number
551600530-001A
AA1
Printed Circuit Board
-
C1
C2
CAP .047UF 630V METAL POLYPRO
CAP 10000PF X7R 250VAC X2 2220
CAP 330UF 35V ELECT PW
EPCOS Inc
B32559C6473K000
GA355DR7GB103KY02L
UPW1V331MPD6
B32921C3104M
Murata Electronics North America
C3, C4
C6
Nichicon
EPCOS
Kemet
CAP .10UF 305VAC EMI SUPPRESSION
C7
CAP, CERM, 0.1µF, 16V, +/-10%, X7R,
0805
C0805C104K4RACTU
C8
C11
C12
C13
D1
CAP CER 47UF 16V X5R 1210
CAP CER 2200PF 50V 10% X7R 0603
CAP CER 330PF 50V 5% C0G 0603
CAP CER 2200PF 250VAC X1Y1 RAD
DIODE TVS 150V 600W UNI 5% SMB
RECT BRIDGE GP 600V 0.5A MINIDIP
DIODE RECT GP 1A 1000V MINI-SMA
DIODE SCHOTTKY 100V 1A SMA
DIODE ZENER 30V 1.5W SMA
MuRata
MuRata
GRM32ER61C476ME15L
GRM188R71H222KA01D
GRM1885C1H331JA01D
CD12-E2GA222MYNS
SMAJ120A
MuRata
TDK Corporation
Littlefuse
D2
Diodes Inc.
RH06-T
D3
Comchip Technology
ST Microelectronics
ON Semiconductor
Fairchild Semiconductor
Diode Inc
CGRM4007-G
D4
STPS1H100A
D5
1SMA5936BT3G
MM5Z12V
D7
DIODE ZENER 12V 200MW
D8
DIODE SWITCH 200V 200MW
BAV20WS-7-F
6125FA
F1
FUSE BRICK 1A 125V FAST 6125FA
Cooper/Bussmann
3M
J1, J2, J3, J4, TP8, 16 GA WIRE HOLE, 18 GA WIRE HOLE
TP9, TP10
923345-02-C
J5, J6
L1, L2
Q1
CONN HEADER .312 VERT 2POS TIN
INDUCTOR 4700UH .13A RADIAL
MOSFET N-CH 600V 90MA SOT-89
MOSFET N-CH 600V 1.8A TO-251
RES 200K OHM 1/4W 5% 1206 SMD
RES, 309k ohm, 1%, 0.25W, 1206
RES, 10.5k ohm, 1%, 0.125W, 0805
RES 4.7 OHM 1/10W 5% 0603 SMD
RES 10 OHM 1/8W 5% 0805 SMD
RES 1.50 OHM 1/4W 1% 1206 SMD
RES 3.48K OHM 1/10W 1% 0603 SMD
RES 191K OHM 1/10W 1% 0603 SMD
RES 40.2 OHM 1/8W 1% 0805 SMD
CURRENT LIMITOR INRUSH 60OHM 20%
Transformer
Tyco Electronics
TDK Corporation
Infineon Technologies
Infineon Technology
Vishay-Dale
1-1318301-2
TSL0808RA-472JR13-PF
BSS225 L6327
Q2
SPU02N60S5
R1, R3
R2, R7
R6, R24
R12
CRCW1206200KJNEA
CRCW1206309KFKEA
CRCW080510K5FKEA
CRCW06034R70JNEA
CRCW080510R0JNEA
CRCW12061R50FNEA
CRCW06033K48FKEA
CRCW0603191KFKEA
CRCW080540R2FKEA
MF72-060D5
Vishay-Dale
Vishay-Dale
Vishay-Dale
R13
Vishay-Dale
R14
Vishay-Dale
R15
Vishay-Dale
R16
Vishay-Dale
R22
Vishay-Dale
RT1
Cantherm
T1
Wurth Electronics
Keystone Electronics
-
750311553 Rev. 01
1502-2
TP2-TP5
TP7
Terminal, Turret, TH, Double
TEST POINT ICT
-
U1
Offline LED Driver, PowerWise
National Semiconductor
LM3444MM
www.national.com
4
Demo Board Wiring Overview
30131143
Wiring Connection Diagram
Test Point
Name
I/O
Description
LED Constant Current Supply
TP3
LED +
Output
Supplies voltage and constant-current to anode of LED string.
TP2
TP5
TP4
LED -
LINE
Output
Input
LED Return Connection (not GND)
Connects to cathode of LED string. Do NOT connect to GND.
AC Line Voltage
Connects directly to AC line of a 120VAC system.
NEUTRAL
Input
AC Neutral
Connects directly to AC neutral of a 120VAC system.
Demo Board Assembly
30131169
Top View
30131170
Bottom View
5
www.national.com
Typical Performance Characteristics (Note 1)
Efficiency vs. Line Voltage
Original Circuit
Efficiency vs. Line Voltage
Modified Circuits
86
86
84
82
80
78
76
84
Original
Mod A
8 LEDs
82
6 LEDs
80
Mod B
Mod C
4 LEDs
78
76
80
90
100 110 120 130 140
80
90
100 110 120 130 140
LINE VOLTAGE (V
)
LINE VOLTAGE (V )
RMS
RMS
30131187
30131189
30131191
30131188
30131190
30131193
LED Current vs. Line Voltage
Original Circuit
LED Current vs. Line Voltage
Modified Circuits
1.0
0.8
0.7
0.4
0.2
0.0
1.0
0.8
0.7
0.4
0.2
0.0
Mod C
Mod B
6 LEDs
4 LEDs
Mod A
8 LEDs
Original
80
90
100 110 120 130 140
80
90
100 110 120 130 140
LINE VOLTAGE (V
)
LINE VOLTAGE (V )
RMS
RMS
Power Factor vs. Line Voltage
Original Circuit
Output Power vs. Line Voltage
Original Circuit
1.000
0.996
0.992
0.988
0.984
0.980
15
12
9
8 LEDs
6 LEDs
6
4 LEDs
3
80
90 100 110 120 130 140
LINE VOLTAGE (V
80
90
100 110 120 130 140
)
LINE VOLTAGE (V )
RMS
RMS
www.national.com
6
Output Power vs. Line Voltage
Modified Circuits
Power MOSFET Drain Voltage Waveform
(VIN = 120VRMS, 6 LEDs, ILED = 350mA)
15
12
9
Mod C
Mod B
6
Mod A
30131196
Original
3
80
90
100 110 120 130 140
LINE VOLTAGE (V
)
RMS
30131194
Current Sense Waveform
(VIN = 120VRMS, 6 LEDs, ILED = 350mA)
FILTER Waveform
(VIN = 120VRMS, 6 LEDs, ILED = 350mA)
30131197
30131198
Note 1: Original Circuit: R14 = 1.50Ω; Modification A: R14 = 1.21Ω; Modification B: R14 = 1.00Ω; Modification C: R14 = 0.75Ω
7
www.national.com
PCB Layout
30131109
Top Layer
30131110
Bottom Layer
www.national.com
8
Transformer Design
Mfg: Wurth Electronics, Part #: 750311553 Rev. 01
30131199
30131114
9
www.national.com
The 120 Hz current ripple flowing through the LED string was
measured to be 170 mApk-pk at full load. The magnitude of the
ripple is a function of the value of energy storage capacitors
connected across the output port. The ripple current can be
reduced by increasing the value of energy storage capacitor
or by increasing the LED string voltage.
Experimental Results
The LED driver is designed to accurately emulate an incan-
descent light bulb and therefore behave as an emulated
resistor. The resistor value is determined based on the LED
string configuration and the desired output power. The circuit
then operates in open-loop, with a fixed duty cycle based on
a constant on-time and constant off-time that is set by select-
ing appropriate circuit components.
The LED driver switching frequency is measured to be close
to the specified 79 kHz. The circuit operates with a constant
duty cycle of 0.28 and consumes 9.25 W of input power. The
driver steady state performance for an LED string consisting
of 6 series LEDs is summarized in the following table.
Performance
In steady state, the LED string voltage is measured to be
21.38 V and the average LED current is measured as 357 mA.
Measured Efficiency and Line Regulation (6 LEDs)
PIN(W) VOUT (V) ILED (mA) POUT (W)
5.37 20.25 216 4.38
VIN (VRMS
90
)
IIN (mARMS
)
Efficiency (%) Power Factor
60
63
66
69
72
75
77
80
82
84
81.6
81.8
81.9
82.1
82.3
82.5
82.7
82.8
82.9
83.0
0.9970
0.9969
0.9969
0.9969
0.9968
0.9967
0.9965
0.9961
0.9957
0.9950
95
5.95
6.57
7.23
7.89
8.59
9.25
9.94
10.62
11.26
20.47
20.67
20.86
21.05
21.23
21.38
21.53
21.68
21.80
238
260
285
309
334
357
382
406
428
4.87
5.38
5.94
6.50
7.09
7.65
8.23
8.80
9.34
100
105
110
115
120
125
130
135
LED Current, Output Power versus Number of LEDs for Various Circuit Modifications ( VIN = 120 VAC
)
# of LEDs
Original Circuit (Note 2)
Modification A (Note 2) Modification B (Note 2) Modification C (Note 2)
ILED (mA)
508
POUT (W)
7.57
ILED (mA)
624
POUT (W)
9.55
ILED (mA)
710
POUT (W)
11.05
ILED (mA)
835
POUT (W)
13.24
4
6
8
357
7.65
440
9.58
500
11.02
590
13.35
277
7.69
337
9.59
382
11.00
445
13.00
Note 2: Original Circuit: R14 = 1.50Ω; Modification A: R14 = 1.21Ω; Modification B: R14 = 1.00Ω; Modification C: R14 = 0.75Ω
design also exhibits low current harmonics as a percentage
of the fundamental current (as shown in the following figure)
and therefore meets the requirements of the IEC 61000-3-2
Class-3 standard.
Power Factor Performance
The LED driver is able to achieve close to unity power factor
(P.F. ~ 0.99) which meets Energy Star requirements. This
Current Harmonic Performance vs. EN/IEC61000-3-2 Class C Lim3i0t1s31195
www.national.com
10
Electromagnetic Interference (EMI)
The EMI input filter of this evaluation board is configured as
shown in the following circuit diagram.
30131167
FIGURE 1. Input EMI Filter and Rectifier Circuit
In order to get a quick estimate of the EMI filter performance,
only the PEAK conductive EMI scan was measured and the
data was compared to the Class B conducted EMI limits pub-
lished in FCC – 47, section 15.
30131177
FIGURE 2. Peak Conductive EMI scan per CISPR-22, Class B Limits
If an additional 33nF of input capacitance (i.e. C6) is utilized
in the input filter, the EMI conductive performance is further
improved as shown in the following figure.
30131178
FIGURE 3. Peak Conductive EMI scan with additional 33nF of input capacitance
11
www.national.com
ILED = 350 mA
Thermal Analysis
The board temperature was measured using an IR camera
(HIS-3000, Wahl) while running under the following condi-
tions:
# of LEDs = 6
POUT = 7.3 W
The results are shown in the following figures.
VIN = 120 VRMS
30131175
FIGURE 4. Top Side Thermal Scan
30131176
FIGURE 5. Bottom Side Thermal Scan
www.national.com
12
By using the line voltage injection technique, the FILTER pin
has the voltage wave shape shown in Figure 7 on it. Voltage
at VFILTER peak should be kept below 1.25V. At 1.25V current
limit is tripped. C11 is small enough not to distort the AC signal
but adds a little filtering.
Circuit Analysis and Explanations
Injecting line voltage into FILTER (achieving PFC > 0.99)
If a small portion (750mV to 1.00V) of line voltage is injected
at FILTER of the LM3444, the circuit is essentially turned into
a constant power flyback as shown in Figure 6.
Although the on-time is probably never truly constant, it can
be observed in Figure 8 how (by adding the rectified voltage)
the on-time is adjusted.
30131118
FIGURE 7. FILTER Waveform
For this evaluation board, the following resistor values are
used:
R2 = R7 = 309kΩ
R15 = 3.48kΩ
Therefore the voltages observed on the FILTER pin will be as
follows for listed input voltages:
30131117
FIGURE 6. Line Voltage Injection Circuit
For VIN = 90VRMS, VFILTER = 0.71V
For VIN = 120VRMS, VFILTER = 0.95V
For VIN = 135VRMS, VFILTER = 1.07V
The LM3444 works as a constant off-time controller normally,
but by injecting the 1.0V rectified AC voltage into the FILTER
pin, the on-time can be made to be constant. With a DCM
Flyback, Δi needs to increase as the input voltage line in-
creases. Therefore a constant on-time (since inductor L is
constant) can be obtained.
Using this technique, a power factor greater than 0.99 can be
achieved without additional passive active power factor con-
trol (PFC) circuitry.
30131116
FIGURE 8. Typical Operation of FILTER Pin
13
www.national.com
Notes
For more National Semiconductor product information and proven design tools, visit the following Web sites at:
www.national.com
Products
www.national.com/amplifiers
Design Support
www.national.com/webench
Amplifiers
WEBENCH® Tools
App Notes
Audio
www.national.com/audio
www.national.com/timing
www.national.com/adc
www.national.com/interface
www.national.com/lvds
www.national.com/power
www.national.com/appnotes
www.national.com/refdesigns
www.national.com/samples
www.national.com/evalboards
www.national.com/packaging
www.national.com/quality/green
www.national.com/contacts
www.national.com/quality
www.national.com/feedback
www.national.com/easy
Clock and Timing
Data Converters
Interface
Reference Designs
Samples
Eval Boards
LVDS
Packaging
Power Management
Green Compliance
Distributors
Switching Regulators www.national.com/switchers
LDOs
www.national.com/ldo
www.national.com/led
www.national.com/vref
www.national.com/powerwise
Quality and Reliability
Feedback/Support
Design Made Easy
Applications & Markets
Mil/Aero
LED Lighting
Voltage References
PowerWise® Solutions
www.national.com/solutions
www.national.com/milaero
www.national.com/solarmagic
www.national.com/training
Serial Digital Interface (SDI) www.national.com/sdi
Temperature Sensors
PLL/VCO
www.national.com/tempsensors SolarMagic™
www.national.com/wireless
PowerWise® Design
University
THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION
(“NATIONAL”) PRODUCTS. NATIONAL MAKES NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY
OR COMPLETENESS OF THE CONTENTS OF THIS PUBLICATION AND RESERVES THE RIGHT TO MAKE CHANGES TO
SPECIFICATIONS AND PRODUCT DESCRIPTIONS AT ANY TIME WITHOUT NOTICE. NO LICENSE, WHETHER EXPRESS,
IMPLIED, ARISING BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL PROPERTY RIGHTS IS GRANTED BY THIS
DOCUMENT.
TESTING AND OTHER QUALITY CONTROLS ARE USED TO THE EXTENT NATIONAL DEEMS NECESSARY TO SUPPORT
NATIONAL’S PRODUCT WARRANTY. EXCEPT WHERE MANDATED BY GOVERNMENT REQUIREMENTS, TESTING OF ALL
PARAMETERS OF EACH PRODUCT IS NOT NECESSARILY PERFORMED. NATIONAL ASSUMES NO LIABILITY FOR
APPLICATIONS ASSISTANCE OR BUYER PRODUCT DESIGN. BUYERS ARE RESPONSIBLE FOR THEIR PRODUCTS AND
APPLICATIONS USING NATIONAL COMPONENTS. PRIOR TO USING OR DISTRIBUTING ANY PRODUCTS THAT INCLUDE
NATIONAL COMPONENTS, BUYERS SHOULD PROVIDE ADEQUATE DESIGN, TESTING AND OPERATING SAFEGUARDS.
EXCEPT AS PROVIDED IN NATIONAL’S TERMS AND CONDITIONS OF SALE FOR SUCH PRODUCTS, NATIONAL ASSUMES NO
LIABILITY WHATSOEVER, AND NATIONAL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY RELATING TO THE SALE
AND/OR USE OF NATIONAL PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR
PURPOSE, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY
RIGHT.
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR
SYSTEMS WITHOUT THE EXPRESS PRIOR WRITTEN APPROVAL OF THE CHIEF EXECUTIVE OFFICER AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
Life support devices or systems are devices which (a) are intended for surgical implant into the body, or (b) support or sustain life and
whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected
to result in a significant injury to the user. A critical component is any component in a life support device or system whose failure to perform
can be reasonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness.
National Semiconductor and the National Semiconductor logo are registered trademarks of National Semiconductor Corporation. All other
brand or product names may be trademarks or registered trademarks of their respective holders.
Copyright© 2010 National Semiconductor Corporation
For the most current product information visit us at www.national.com
National Semiconductor
Americas Technical
Support Center
National Semiconductor Europe
Technical Support Center
Email: europe.support@nsc.com
National Semiconductor Asia
Pacific Technical Support Center
Email: ap.support@nsc.com
National Semiconductor Japan
Technical Support Center
Email: jpn.feedback@nsc.com
Email: support@nsc.com
Tel: 1-800-272-9959
www.national.com
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements,
and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should
obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are
sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard
warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where
mandated by government requirements, testing of all parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and
applications using TI components. To minimize the risks associated with customer products and applications, customers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right,
or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information
published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a
warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual
property of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied
by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive
business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional
restrictions.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all
express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not
responsible or liable for any such statements.
TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably
be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing
such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products
and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be
provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in
such safety-critical applications.
TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are
specifically designated by TI as military-grade or "enhanced plastic." Only products designated by TI as military-grade meet military
specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at
the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use.
TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are
designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated
products in automotive applications, TI will not be responsible for any failure to meet such requirements.
Following are URLs where you can obtain information on other Texas Instruments products and application solutions:
Products
Audio
Applications
www.ti.com/audio
amplifier.ti.com
dataconverter.ti.com
www.dlp.com
Communications and Telecom www.ti.com/communications
Amplifiers
Data Converters
DLP® Products
DSP
Computers and Peripherals
Consumer Electronics
Energy and Lighting
Industrial
www.ti.com/computers
www.ti.com/consumer-apps
www.ti.com/energy
dsp.ti.com
www.ti.com/industrial
www.ti.com/medical
www.ti.com/security
Clocks and Timers
Interface
www.ti.com/clocks
interface.ti.com
logic.ti.com
Medical
Security
Logic
Space, Avionics and Defense www.ti.com/space-avionics-defense
Transportation and Automotive www.ti.com/automotive
Power Mgmt
Microcontrollers
RFID
power.ti.com
microcontroller.ti.com
www.ti-rfid.com
Video and Imaging
www.ti.com/video
OMAP Mobile Processors www.ti.com/omap
Wireless Connectivity www.ti.com/wirelessconnectivity
TI E2E Community Home Page
e2e.ti.com
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2011, Texas Instruments Incorporated
LM3401,LM3402,LM3402HV,LM3404,LM3404HV,
LM3405,LM3405A,LM3406,LM3406HV,LM3407,
LM3409,LM3409HV,LM3410,LM3414,LM3414HV,
LM3421,LM3423,LM3424,LM3429,LM3430,
LM3431,LM3433,LM3434,LM3435,LM3444,
LM3445,LM3450,LM3464,LM3492,LM5022
Application Note 1656 Design Challenges of Switching LED Drivers
Literature Number: SNVA253
National Semiconductor
Application Note 1656
Chris Richardson
Design Challenges of
Switching LED Drivers
October 2007
Using a switching regulator as an LED driver requires the de-
signer to convert a voltage regulator into a current regulator.
Beyond the challenge of changing the feedback system to
control current, the LEDs themselves present a load charac-
teristic that is much different than the digital devices and other
loads that require constant voltage. The LED WEBENCH®
online design environment predicts and simulates the re-
sponse of an LED to constant current while taking into ac-
count several potential design parameters that are new to
designers of traditional switching regulators.
Once the VF of the LEDs has been determined from the V-I
curve, the LED driver’s output voltage is calculated using the
following formula:
VO = n x VF + VSNS
In this equation, 'n' is the number of LEDs connected in series,
and 'VSNS' is the voltage drop across the current sense resis-
tor.
Designing for VO-MIN and VO-MAX
In practice, the typical value of VF changes with forward cur-
rent. Further analysis of total output voltage is needed be-
cause VF also changes with process and with the LED die
temperature. The more LEDs in series, the larger the potential
difference between VO-MIN, VO-TYP and VO-MAX. An LED driver
must therefore be able to vary output voltage over a wide
range to maintain a constant current. IF is the controlled pa-
rameter, but minimum and maximum output voltage must be
predicted in order to select the proper regulator topology, IC,
and passive components.
Output Voltage Changes when LED
Current Changes
In the first step of the LED WEBENCH tool, "Choose Your
LEDs", an LED is selected with a standard forward current,
IF. This default value is provided by the LED manufacturers,
and in most cases it represents the testing condition for that
LED. Typical values for high-power LEDs are 350 mA, 700
mA, and 1000 mA.
30025102
30025101
FIGURE 2. VIN-MIN > VO-TYP, Buck Regulator Works
FIGURE 1. V-I Curve with Typical VF and IF
A typical example that can lead to trouble is driving three white
(InGaN) LEDs from an input voltage of 12V ±5%. In Figure
2, each LED operates at the typical VF of 3.5V, and the current
sense adds 0.2V for a VO of 10.7V. Minimum input voltage is
95% of 12V, or 11.4V, meaning that a buck regulator capable
of high duty cycle could be used to drive the LEDs.
Not all designs will use a standard current, however. The de-
signer can select a different LED current, and then the forward
voltage will change in the VLED box under step 2. The change
in voltage comes from LEDs’ V-I curve. Figure 1 shows a
curve from a 5W white (InGaN) LED that differs from the
curves normally found in LED datasheets. LED manufactur-
ers provide these curves, but they are often shown as I-V
curves with voltage as the independent quantity. In Figure 1,
forward current is the independent variable, reflecting the fact
that in LED drivers current is controlled, and voltage is allowed
to vary. The cross-hairs intersect at the standard/typical IF and
VF values of 350 mA and 3.5V, respectively.
However, a buck regulator designed for the typical VO will be
unable to control IF if VO-MAX exceeds the minimum input volt-
age. The same white LEDs with a typical VF of 3.5V have a
VF-MAX of 4.0V. Headroom is tight under typical conditions,
and the buck regulator will lose regulation with only a small
increase in VF from one or more of the LEDs (Figure 3).
WEBENCH® is a registered trademark of National Semiconductor Corporation.
© 2007 National Semiconductor Corporation
300251
www.national.com
To maintain safety and reliability in a parallel LED system,
forward voltage should be binned or matched. Fault monitor-
ing should detect LEDs that fail as either short or open circuits.
Finally, the entire array should have evenly distributed heat
sinking, to ensure that VF change with respect to die temper-
ature occurs uniformly over all the LEDs.
Selecting LED Ripple Current
LED ripple current, ΔiF, in an LED driver is the equivalent of
output voltage ripple, ΔvO, in a voltage regulator. In general,
the requirements for ΔiF are not as tight as output voltage rip-
ple. Where a ripple of a few milivolts to 4%P-P of VO is typical
for ΔvO, ripple currents for LED drivers range from 10% to
40%P-P of the average forward current, IF.Figure 5 and Figure
6 show a typical ripple current of 25%P-P from a buck switching
LED driver. A wider tolerance for ΔiF is acceptable because
the ripple is too high in frequency for the human eye to see.
General illumination applications (Such as lamps, flashlights,
signs, etc.) can tolerate large ripple currents without harming
the quality or character of the light. Allowing larger ripple cur-
rent means lower inductance and capacitance for the output
filter, which in turn translates to smaller PCB footprints and
lower BOM costs. For this reason, ΔiF should generally be
made as large as the application permits.
30025103
FIGURE 3. VIN-MIN < VO-MAX, Buck Regulator Fails to
Regulate
Pitfalls of Parallel LED Arrays
Whenever LEDs are placed in parallel, the potential exists for
a mismatch in the current that flows through the different
branches. The forward voltage, VF, of each LED varies with
process, so unless each LED is binned or selected to match
VF, the LED or LED string with the lowest total forward voltage
will draw the most current (Figure 4). This problem is com-
pounded by the negative temperature coefficient of LEDs
(and all PN junction diodes). The LEDs that draw the most
current suffer the greatest increase in die temperature. As
their die temperature increases, their VF decreases, creating
a positive feedback loop. Elevated die temperature both re-
duces the light output and decreases the lifetime of the LEDs.
The true upper limit for ΔiF comes from the nonlinear propor-
tion of heat to light that is generated as the peak current
through the LED increases. Above approximately 40%P-P rip-
ple, the LED can experience more heating during the peaks
than cooling during the valleys, resulting in higher die tem-
perature and reduction in LED lifetime.
Some high-end applications require tighter control over LED
ripple current. These include industrial inspection, machine
vision, and blending of red, green, and blue for backlighting
or video projection. The higher system cost of these applica-
tions justifies larger, more expensive filtering to achieve ripple
currents in the sub 10%P-P region.
The system in Figure 4 also illustrates a potential over-current
condition if one of the LEDs fails as an open circuit. Without
some protection scheme, the entire drive current IO will flow
through the remaining LED(s), likely causing thermal over-
stress. Likewise, if one of the LEDs fails as a short circuit, the
total forward voltage of that string will drop significantly, caus-
ing higher current to flow through the affected branch.
30025105
FIGURE 5. LED Current (DC and AC)
30025104
FIGURE 4. Mismatched LEDs in Parallel
www.national.com
2
30025106
FIGURE 6. Only LED Ripple Current
30025107
FIGURE 7. VF vs IF
Dynamic Resistance
Load resistance is an important parameter in power supply
design, particularly for the control loop. In LED drivers it is also
used to select the output capacitance needed to achieve the
desired LED ripple current. In a standard power supply that
regulates output voltage, the load resistance has a simple
calculation:
RO = VO / IO
When the load is an LED or string of LEDs, however, the load
resistance is replaced with the dynamic resistance, rD and the
current sense resistor. LEDs are PN junction diodes, and their
dynamic resistance shifts as their forward current changes.
Dividing VF by IF leads to incorrect results that are 5 to 10
times higher than the true rD value.
Typical dynamic resistance at a specified forward current is
provided by some manufacturers, but in most cases it must
be calculated using I-V curves. (All LED manufacturers will
provide at least one I-V curve.) To determine rD at a certain
forward current, draw a line tangent to the I-V slope as shown
in Figure 7. Extend the line to the edges of the plot and record
the change in forward voltage and forward current. Dividing
ΔVF by ΔIF provides the rD value at that point. Figure 8 shows
a plot of several rD values plotted against forward current to
demonstrate how much rD shifts as the forward current
changes.
30025108
FIGURE 8. rD vs IF
Dynamic resistances combine in series and parallel like linear
resistors, hence for a string of 'n' series-connected LEDs the
total dynamic resistance would be:
One amp is a typical driving current for 3W LEDs, and the
calculation below shows how the dynamic resistance of a 3W
white InGaN was determined at 1A:
rD-TOTAL = n x rD + RSNS
A curve-tracer capable of the 1A+ currents used by high pow-
er LEDs can be used to draw the I-V characteristic of an LED.
If the curve tracer is capable of high current and high voltage,
it can also be used to draw the complete I-V curve of the entire
LED array. Total rD can determined using the tangent-line
method from that plot. In the absence of a high-power curve
tracer, a laboratory bench-top power supply can be substitut-
ed by driving the LED or LED array at several forward currents
and measuring the resulting forward voltages. A plot is cre-
ated from the measured points, and again the tangent line
method is used to find rD.
ΔVF = 3.85V – 3.48V
ΔIF = 1.5A – 0A
rD = ΔVF / ΔIF = 0.37 / 1.5 = 0.25Ω
3
www.national.com
Notes
THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION
(“NATIONAL”) PRODUCTS. NATIONAL MAKES NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY
OR COMPLETENESS OF THE CONTENTS OF THIS PUBLICATION AND RESERVES THE RIGHT TO MAKE CHANGES TO
SPECIFICATIONS AND PRODUCT DESCRIPTIONS AT ANY TIME WITHOUT NOTICE. NO LICENSE, WHETHER EXPRESS,
IMPLIED, ARISING BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL PROPERTY RIGHTS IS GRANTED BY THIS
DOCUMENT.
TESTING AND OTHER QUALITY CONTROLS ARE USED TO THE EXTENT NATIONAL DEEMS NECESSARY TO SUPPORT
NATIONAL’S PRODUCT WARRANTY. EXCEPT WHERE MANDATED BY GOVERNMENT REQUIREMENTS, TESTING OF ALL
PARAMETERS OF EACH PRODUCT IS NOT NECESSARILY PERFORMED. NATIONAL ASSUMES NO LIABILITY FOR
APPLICATIONS ASSISTANCE OR BUYER PRODUCT DESIGN. BUYERS ARE RESPONSIBLE FOR THEIR PRODUCTS AND
APPLICATIONS USING NATIONAL COMPONENTS. PRIOR TO USING OR DISTRIBUTING ANY PRODUCTS THAT INCLUDE
NATIONAL COMPONENTS, BUYERS SHOULD PROVIDE ADEQUATE DESIGN, TESTING AND OPERATING SAFEGUARDS.
EXCEPT AS PROVIDED IN NATIONAL’S TERMS AND CONDITIONS OF SALE FOR SUCH PRODUCTS, NATIONAL ASSUMES NO
LIABILITY WHATSOEVER, AND NATIONAL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY RELATING TO THE SALE
AND/OR USE OF NATIONAL PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR
PURPOSE, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY
RIGHT.
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR
SYSTEMS WITHOUT THE EXPRESS PRIOR WRITTEN APPROVAL OF THE CHIEF EXECUTIVE OFFICER AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
Life support devices or systems are devices which (a) are intended for surgical implant into the body, or (b) support or sustain life and
whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected
to result in a significant injury to the user. A critical component is any component in a life support device or system whose failure to perform
can be reasonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness.
National Semiconductor and the National Semiconductor logo are registered trademarks of National Semiconductor Corporation. All other
brand or product names may be trademarks or registered trademarks of their respective holders.
Copyright© 2007 National Semiconductor Corporation
For the most current product information visit us at www.national.com
National Semiconductor
Americas Customer
Support Center
National Semiconductor Europe
Customer Support Center
Fax: +49 (0) 180-530-85-86
National Semiconductor Asia
Pacific Customer Support Center
Email: ap.support@nsc.com
National Semiconductor Japan
Customer Support Center
Fax: 81-3-5639-7507
Email:
new.feedback@nsc.com
Tel: 1-800-272-9959
Email: europe.support@nsc.com
Deutsch Tel: +49 (0) 69 9508 6208
English Tel: +49 (0) 870 24 0 2171
Français Tel: +33 (0) 1 41 91 8790
Email: jpn.feedback@nsc.com
Tel: 81-3-5639-7560
www.national.com
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements,
and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should
obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are
sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard
warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where
mandated by government requirements, testing of all parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and
applications using TI components. To minimize the risks associated with customer products and applications, customers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right,
or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information
published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a
warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual
property of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied
by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive
business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional
restrictions.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all
express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not
responsible or liable for any such statements.
TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably
be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing
such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products
and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be
provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in
such safety-critical applications.
TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are
specifically designated by TI as military-grade or "enhanced plastic." Only products designated by TI as military-grade meet military
specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at
the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use.
TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are
designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated
products in automotive applications, TI will not be responsible for any failure to meet such requirements.
Following are URLs where you can obtain information on other Texas Instruments products and application solutions:
Products
Audio
Applications
www.ti.com/audio
amplifier.ti.com
dataconverter.ti.com
www.dlp.com
Communications and Telecom www.ti.com/communications
Amplifiers
Data Converters
DLP® Products
DSP
Computers and Peripherals
Consumer Electronics
Energy and Lighting
Industrial
www.ti.com/computers
www.ti.com/consumer-apps
www.ti.com/energy
dsp.ti.com
www.ti.com/industrial
www.ti.com/medical
www.ti.com/security
Clocks and Timers
Interface
www.ti.com/clocks
interface.ti.com
logic.ti.com
Medical
Security
Logic
Space, Avionics and Defense www.ti.com/space-avionics-defense
Transportation and Automotive www.ti.com/automotive
Power Mgmt
Microcontrollers
RFID
power.ti.com
microcontroller.ti.com
www.ti-rfid.com
Video and Imaging
www.ti.com/video
OMAP Mobile Processors www.ti.com/omap
Wireless Connectivity www.ti.com/wirelessconnectivity
TI E2E Community Home Page
e2e.ti.com
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2011, Texas Instruments Incorporated
National Semiconductor
2900 Semiconductor Dr.
Santa Clara, CA 95052
M Reynolds, David Zhang
Applications Engineer
SSL Division - Longmont,
CO 80501
LM3444 MR16 Boost Reference Design for
Non-Dimming & Dimming LED Applications
March 31, 2011
Revision 1.0a
NATIONAL SEMICONDUCTOR
Page 1 of 20
Table of Contents
MR16 Halogen/SSL Retro-Fit Analysis ......................................................................................................................3
Differences between Magnetic and Electronic Transformers .................................................................................................... 3
SSL MR16 lamps compatibility concerns with ELVT and ELV dimmers (true retro-fit)............................................................... 3
Halogen vs SSL MR16 waveforms ............................................................................................................................................... 4
Halogen MR16 ..............................................................................................................................................................5
LM3444 MR16 Boost Reference Design ....................................................................................................................7
Operating Specifications............................................................................................................................................................. 7
Schematic.................................................................................................................................................................................... 8
PCB Layout .................................................................................................................................................................................. 8
Bill of Materials........................................................................................................................................................................... 9
Typical Performance ................................................................................................................................................................ 10
Dimming Waveforms ................................................................................................................................................................ 13
Thermal Analysis .......................................................................................................................................................15
Reference Design Transformer Compatibility ........................................................................................................16
Performance with and without Transformer ...........................................................................................................17
Revision History.........................................................................................................................................................20
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 2 of 20
MR16 Halogen/SSL Retro-Fit Analysis
Differences between Magnetic and Electronic Transformers
Magnetic Transformers
Magnetic transformers step down 120VAC line voltage to 12VAC. Magnetic transformers consist only of magnetic
core, and copper wire, no electronics are used to step down the voltage from 120VAC to 12VAC. Due to the fact
that the frequency of operation is 50Hz or 60Hz, the size of the Magnetic transformers is large and heavy. Magnetic
transformers are primarily available in two types of construction; torroidal and laminated EI core.
With existing Halogen MR16 systems that require dimming, Magnetic Low Voltage Dimmers are required to be
used.
Electronic Transformers
Electronic transformers also step down 120VAC line voltage to 12VAC. Electronic transformers are much smaller
and more efficient than magnetic transformers. Electronic transformers are more common than magnetic
transformers in existing Halogen MR16 system. Electronic Low Voltage Transformers (ELVT) consists of a small
self resonant tank power supply. Electronic Low Voltage Dimmers (ELV dimmers) are used with ELVT for dimming
systems.
Although electronic transformers are more complex, with many more components, that their magnetic counterparts,
electronic transformers are far less expensive and smaller. The shear amount of core material and copper within a
magnetic transformer adds cost, and the weight of the product makes it expensive to manufacture, and ship.
SSL MR16 lamps compatibility concerns with ELVT and ELV dimmers (true retro-fit)
Electronic transformers modulate (PWM) the input AC voltage with a frequency of 35 kHz to150 kHz. This
waveform is step-down from 120V or 230V (typical) to 12VAC with a transformer. The higher switching frequency
allows for the smaller magnetic components, and the overall smaller design. As mentioned earlier, the electronic
transformer is a self driven resonant half bridge topology. The self resonance half-bridge topology requires the
converter to have a minimal load at all times to function properly. Common minimum loads for ELV dimmers are
from 6W – 12W depending on manufacture, and maximum power rating of the ELVT. With traditional Halogen
lamps, the minimal load is of no concern, common Halogen MR16 lamps use about 50W of power per lamp. These
lamps are very inefficient, and 10W of Halogen power produces very little light.
With the current efficacy of the LEDs above 100 lumens per watt, 6W of SSL power is equivalent to about 40W to
50W of Halogen power. One can quickly see the compatibility issue of SSL MR16 lamps and the ELVT’s. If the
output power of the ELVT reduces below the minimum requirement, the ELV dimmer will stop operating. The
turning on, and off of the ELVT will cause visible flicker from the SSL MR16 lamp, and could also cause reliability
issues with the lamp or ELVT.
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 3 of 20
Halogen vs SSL MR16 waveforms
Halogen MR16 waveforms
Channel - 1 (yellow trace) = Input line voltage
Channel - 3 (purple trace) = Input line current
Channel - 4 (green trace) = bulb current
Improper SSL MR16 operating waveform
Issue #1 - The two scope captures above illustrate the SSL MR16 technical challenges. Figure one shows typical
Halogen MR16 waveforms, and figure two is common MR16 replacement bulbs waveforms. The SSL replacement
bulb looks capacitive to the ELVT; therefore large current spikes charge the energy storage device within the SSL
MR16 bulb. The switching converter within the bulb then processes the input power from the energy storage
element to the LED load. At this time the minimum load requirement of the ELVT is not satisfied, and the ELVT
turns off. Once the energy is depleted within the MR16 converter, the ELVT will start up, and the process cycles.
The turning off/on of the ELVT will manifest itself as visible flicker.
Issue #2 – The maximum input current to the Halogen bulb is approximately 4.25A. The maximum input current to
the SSL bulb is approximately 12A. The large magnitude spike associated with charging the SSL MR16 input
capacitor can cause premature failures within the SSL bulb, or even the ELVT.
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 4 of 20
Halogen MR16
Summary: No flickering observed. There is a delay (1.12ms, 24° angle) from when the supply voltage starts
ramping up from zero volts to when the electronic transformer starts to operate and the bulb turns on. This delay
shows up on the LED MR16s as well although the magnitude of delay does vary from bulb to bulb. No current
spikes observed out of the transformer.
The bench set-up diagram below was used in the evaluation of the halogen MR16 bulb. The following scope plots
show voltage and current waveforms designated by the labels indicated in the bench set-up diagram. The
electronic transformer used was the Lightech LET-75.
Bench Circuit
12V, 50W Halogen
MR16 Bulb
IBULB
IIN
LINE
LINE
+12V
120VAC
Power
Supply
Transformer
VIN
(Electronic)
NEUTRAL
NEUTRAL
SGND
VBULB
VIN (Yellow), IIN (Magenta), IBULB (Green)
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 5 of 20
VIN (Yellow), IIN (Magenta), IBULB (Green)
VBULB (Blue), IBULB (Green)
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 6 of 20
LM3444 Boost MR16 Reference Design
This reference design was based on the released LM3444 IC from National Semiconductor.
This design was developed to minimize the current spikes coming out of an electronic transformer to less than 5A,
which is a typical transformer rating, when driving an LED MR16 circuit. The off the shelf LED MR16 solutions
exhibit spikes that significantly exceed a transformer’s maximum rated output current which will degrade the
reliability of the transformer and reduce its operating lifetime.
This design generates a continuous LED current when a 220uF 35V electrolytic capacitor is placed across the
output. The circuit operates in a constant output power mode. The output power is fixed at about 6W.
Operating Specifications
NOTE: The following specifications are typical values based on the LED driver being powered directly by a 12VAC
supply (i.e. no electronic or magnetic step-down transformer).
Input Voltage, VIN: ............................................................................................................................................. 12 VAC
Output Voltage, VOUT: ...................................................................................................23.5V (Single string of 7 LEDs)
Input Current, IIN .................................................................................................................................................. 710mA
LED Output Current, ILED ..................................................................................................................................... 280mA
Input Power, PIN .................................................................................................................................................. ~ 8.0W
Output Power, POUT ............................................................................................................................................. ~ 6.6W
Efficiency ............................................................................................................................................................. ~ 83 %
Power Factor ........................................................................................................................................................ ~ 0.95
Input Voltage, VIN: ............................................................................................................................................. 12 VAC
Output Voltage, VOUT: ...................................................................................................26.6V (Single string of 8 LEDs)
Input Current, IIN .................................................................................................................................................. 680mA
LED Output Current, ILED ..................................................................................................................................... 240mA
Input Power, PIN .................................................................................................................................................. ~ 7.7W
Output Power, POUT ............................................................................................................................................. ~ 6.4W
Efficiency ............................................................................................................................................................. ~ 83 %
Power Factor ........................................................................................................................................................ ~ 0.95
Input Voltage, VIN: ............................................................................................................................................. 12 VAC
Output Voltage, VOUT: ...................................................................................................28.2V (Single string of 9 LEDs)
Input Current, IIN .................................................................................................................................................. 670mA
LED Output Current, ILED ..................................................................................................................................... 220mA
Input Power, PIN .................................................................................................................................................. ~ 7.5W
Output Power, POUT ............................................................................................................................................. ~ 6.2W
Efficiency ............................................................................................................................................................. ~ 83 %
Power Factor ........................................................................................................................................................ ~ 0.95
SMPS Topology .................................................................................................................................................... Boost
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 7 of 20
PCB Schematic
PCB Layout
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 8 of 20
Bill of Materials
Designator
Description
MFG
Part Number
C1
CAP, CERM, 1.0uF, 25V, +/-10%, X5R, 0805
CAP, ELECT, 220uF, 35V, +/-20%, Radial 8x11.5mm
CAP, CERM, 22uF, 25V, +/-10%, X5R, 1210
CAP, CERM, 330pF, 100V, +/-5%, X7R, 0603
CAP, CERM, 4.7uF, 50V, +/-10%, X7R, 1210
CAP, CERM, 4.7uF, 25V, +/-10%, X5R, 0805
Diode, Schottky, 30V, 3A, SMA
MuRata
Panasonic
MuRata
AVX
GRM216R61E105KA12D
ECA-1VHG221
C2
C3
GRM32ER61E226KE15L
06031C331JAT2A
GRM32ER71H475KA882
GRM21BR61E475KA12L
B330A-13-F
C4
C5
MuRata
MuRata
C6
D1-D4
D5
D6
D7
D8
L1
Diodes Inc.
Diode, Schottky, 60V, 1A, SMA
Diodes Inc.
B160-13-F
TVS BI-DIR 24V 400W SMA (Optional)
Diode, Zener, 11V, 500mW, SOD-123
Diode, Zener, 33V, 500mW, SOD-123
Ind, Shielded Drum Core, Ferrite, 33uH, 1.1A, 0.31 ohm, SMD
Transistor, NPN, 80V, 500mA, SOT-23
MOSFET, N-CH, 60V, 1.2A, SOT-23
Diodes Inc
SMAJ24CA-13-F
CMHZ4698
Central Semiconductor
Central Semiconductor
CMHZ4714
MSS6132-333MLB
Coilcraft
Central Semiconductor
Q1
Q2
R1
CMPTA06
Diodes Inc.
ZXMN6A07FTA
ERJ-6RSJR10V
RES, 0.1 ohm, 5%, 0.125W, 0805
Panasonic
R2, R4
R3
RES, 1.00k ohm, 1%, 0.1W, 0603
RES, 12.4k ohm, 1%, 0.1W, 0603
RES, 1.00 ohm, 1%, 0.5W, 1206
RES, 4.7 ohm, 5%, 0.125W, 0805
Vishay-Dale
Vishay-Dale
Stackpole Electronics Inc
Yageo
CRCW06031K00FKEA
CRCW060312k4FKEA
CSR1206FK1R00
R5
RC0805JR-074R7L
R6
U1
AC-DC Off Line LED Driver
National Semiconductor
LM3444MM
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 9 of 20
Typical Performance (Eight series LEDs)
Bench Circuit
I1
I3
I2
LINE
Vp
Vp
Vs
VIN
LED+
LED
Board
120VAC
Power
Supply
LM3444 MR16
LED Driver
Transformer
V3
V1
V2
(Electronic)
Vs
LED-
NEUTRAL
VIN
The following scope plots show voltage and current waveforms designated by the labels indicated in the following
bench set-up diagram. The electronic transformer used was the Lightech LET-75.
CH2 V1 Voltage, CH4 I3 Current
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 10 of 20
CH2 V1 Voltage, CH4 I2 Current
4.4A peak
CH2 V1 Voltage, CH4 I2 Current
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 11 of 20
CH2 V2 Voltage, CH4 I2 Current
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 12 of 20
LM3444 MR16 Boost evaluation board Dimming Waveforms
Bench Circuit
I4
I1
I3
I2
LINE
Vp
Vs
VIN
LED+
LED
120VAC
Power
Supply
Board
Triac
Dimmer
Transformer
LM3444 MR16
LED Driver
V4
V1
V3
V2
( Electronic )
NEUTRAL
Vs
LED-
VIN
Vp
This LM3444 MR16 Boost evaluation board is designed to operate (flicker-free) with common Electronic Low
Voltage dimmers, and Electronic Transformers.
Dimmer Used – Lutron SELV-300P-GR
Electronic Transformer – Lightech LET75
20:1 dimming ratio
LM3444 MR16 Boost - Eight series connected LEDs at 200mA (90° Conduction Angle)
CH2 V2 Voltage, CH4 I4 Current
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 13 of 20
LM3444 MR16 Boost - Eight series connected LEDs at 100mA (45° Conduction Angle)
CH2 V2 Voltage, CH4 I4 Current
LM3444 MR16 Boost - Eight series connected LEDs at 10mA (minimum Conduction Angle)
CH2 V2 Voltage, CH4 I4 Current
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 14 of 20
Thermal Analysis
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 15 of 20
Reference Design Transformer Compatibility
The following transformers were tested with the National LED driver designs described in this document. A
compatibility matrix is shown below which describes which driver/transformer combinations are suitable (i.e. no
flicker, stable operation).
Electronic Transformers (120VAC to 12VAC):
Lightech, Model: LET-60, 60W
Lightech, Model: LET-75, 75W
Lightech, Model: LET-60 LW, 60W
Hatch, Model: RS12-80M, 80W
Hatch, Model: RS12-60, 60W
Pony, Model: PET-120-12-60, 60W
Eurofase, Model: 0084 CLASS 2, 60W
Magnetic Transformers (120VAC to 12VAC):
Hatch, Model: LS1275EN, 75VA
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 16 of 20
Performance with 7 LEDs
Performance without transformer
The table below compares the performance of each reference design when powered directly by a 12VAC source
LM3441 BOOST 7 LEDs
Specs
VIN
Units
11.91
0.708
7.97
VAC
IIN
A
W
VDC
A
PIN
(1)
VOUT
23.55
0.281
6.62
(1)
ILED
(2)
POUT
W
-
Efficiency
83.0%
0.948
Power Factor
-
Performance with transformer
LET-75
LM3444 BOOST 7 LEDs
Specs
VIN
Units
120
0.07
VAC
IIN
A
W
VDC
A
8.18
PIN
(1)
23.5
VOUT
(1)
0.270
6.23
ILED
(2)
POUT
W
-
Efficiency
77.6%
0.970
Power Factor
-
HATCH RS12-80M
LM3444 BOOST 7 LEDs
Specs
VIN
Units
120
0.072
8.13
VAC
IIN
A
W
VDC
A
PIN
23.5
VOUT
0.270
6.23
ILED
POUT
W
-
Efficiency
Power Factor
78.0%
0.934
-
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 17 of 20
Performance with 8 LEDs
Performance without transformer
The table below compares the performance of each reference design when powered directly by a 12VAC source
LM3441 BOOST 8 LEDs
Specs
VIN
Units
11.91
0.682
7.66
VAC
IIN
A
W
VDC
A
PIN
(1)
VOUT
26.64
0.238
6.34
(1)
ILED
(2)
POUT
W
-
Efficiency
82.8%
0.946
Power Factor
-
Performance with transformer
LET-75
LM3444 BOOST 8 LEDs
Specs
VIN
Units
120
0.067
7.86
VAC
IIN
A
W
VDC
A
PIN
26.5
VOUT
0.230
6.10
ILED
POUT
W
-
Efficiency
Power Factor
77.5%
0.970
-
HATCH RS12-80M
LM3444 BOOST 8 LEDs
Specs
VIN
Units
120
0.069
7.82
VAC
IIN
A
W
VDC
A
PIN
26.5
VOUT
0.230
6.10
ILED
POUT
W
-
Efficiency
Power Factor
77.9%
0.930
-
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 18 of 20
Performance with 9 LEDs
Performance without transformer
The table below compares the performance of each reference design when powered directly by a 12VAC source
LM3441 BOOST 9 LEDs
Specs
VIN
Units
11.92
0.668
7.51
VAC
IIN
A
W
VDC
A
PIN
(1)
VOUT
28.25
0.220
6.22
(1)
ILED
(2)
POUT
W
-
Efficiency
82.8%
0.946
Power Factor
-
Performance with transformer
LET-75
LM3444 BOOST 9 LEDs
Specs
VIN
Units
120
0.066
7.74
VAC
IIN
A
W
VDC
A
PIN
28.0
VOUT
0.215
6.02
ILED
POUT
W
-
Efficiency
Power Factor
77.8%
0.970
-
HATCH RS12-80M
LM3444 BOOST 9 LEDs
Specs
VIN
Units
120
0.068
7.64
VAC
IIN
A
W
VDC
A
PIN
28.0
VOUT
0.212
5.94
ILED
POUT
W
-
Efficiency
Power Factor
77.7%
0.930
-
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 19 of 20
Revision History
Date
Author
Revision
Description
LM3444-MR16-Boost Reference Design NATIONAL SEMICONDUCTOR
Page 20 of 20
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements,
and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should
obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are
sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard
warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where
mandated by government requirements, testing of all parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and
applications using TI components. To minimize the risks associated with customer products and applications, customers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right,
or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information
published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a
warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual
property of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied
by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive
business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional
restrictions.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all
express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not
responsible or liable for any such statements.
TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably
be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing
such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products
and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be
provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in
such safety-critical applications.
TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are
specifically designated by TI as military-grade or "enhanced plastic." Only products designated by TI as military-grade meet military
specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at
the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use.
TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are
designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated
products in automotive applications, TI will not be responsible for any failure to meet such requirements.
Following are URLs where you can obtain information on other Texas Instruments products and application solutions:
Products
Audio
Applications
www.ti.com/audio
amplifier.ti.com
dataconverter.ti.com
www.dlp.com
Automotive and Transportation www.ti.com/automotive
Communications and Telecom www.ti.com/communications
Amplifiers
Data Converters
DLP® Products
DSP
Computers and Peripherals
Consumer Electronics
Energy and Lighting
Industrial
www.ti.com/computers
www.ti.com/consumer-apps
www.ti.com/energy
dsp.ti.com
Clocks and Timers
Interface
www.ti.com/clocks
interface.ti.com
logic.ti.com
www.ti.com/industrial
www.ti.com/medical
www.ti.com/security
Medical
Logic
Security
Power Mgmt
Microcontrollers
RFID
power.ti.com
Space, Avionics and Defense www.ti.com/space-avionics-defense
microcontroller.ti.com
www.ti-rfid.com
Video and Imaging
www.ti.com/video
OMAP Mobile Processors www.ti.com/omap
Wireless Connectivity www.ti.com/wirelessconnectivity
TI E2E Community Home Page
e2e.ti.com
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2012, Texas Instruments Incorporated
相关型号：
©2020 ICPDF网 联系我们和版权申明