LM3434SQX/NOPB [TI]
Common Anode Capable High Brightness LED Driver with High Frequency Dimming;
| 型号： | LM3434SQX/NOPB |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | Common Anode Capable High Brightness LED Driver with High Frequency Dimming 驱动 接口集成电路 |
| 文件： | 总20页 (文件大小：821K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LM3434
www.ti.com
SNVS619B –MARCH 2010–REVISED MAY 2013
Common Anode Capable High Brightness LED Driver with High Frequency Dimming
Check for Samples: LM3434
1
FEATURES
DESCRIPTION
The LM3434 is an adaptive constant on-time DC/DC
buck (step-down) constant current controller (a true
current source). The LM3434 provides a constant
current for illuminating high power LEDs. The output
configuration allows the anodes of multiple LEDs to
be tied directly to the ground referenced chassis for
maximum heat sink efficacy. The high frequency
capable architecture allows the use of small external
passive components and no output capacitor while
maintaining low LED ripple current. Two control
inputs are used to modulate LED brightness. An
analog current control input is provided so the
LM3434 can be adjusted to compensate for LED
manufacturing variations and/or color temperature
correction. The other input is a logic level PWM
control of LED current. The PWM functions by
shorting out the LED with a parallel switch allowing
high PWM dimming frequencies. High frequency
PWM dimming allows digital color temperature
control, interference blanking, field sequential
illumination, and brightness control. Additional
features include thermal shutdown, VCC under-voltage
lockout, and logic level shutdown mode. The LM3434
is available in a low profile 24-pin WQFN package.
2
•
Operating Input Voltage Range of –9V to -30V
w.r.t. LED Anode
•
Control Inputs are Referenced to the LED
Anode
•
•
•
Output Current Greater than 6A
Greater than 30kHz PWM Frequency Capable
Negative Output Voltage Capability Allows
LED Anode to be Tied Directly to Chassis for
Maximum Heat Sink Efficiency
•
•
•
•
•
No Output Capacitor Required
Up to 1MHz Switching Frequency
Low IQ, 1mA Typical
Soft Start
Adaptive Programmable ON Time Allows for
Constant Ripple Current
•
24-Pin WQFN Package
APPLICATIONS
•
•
•
Projection Systems
Solid State Lighting
Automotive Lighting
TYPICAL APPLICATION CIRCUIT
0.1
mF
LED ANODE
44.2k
Q3
Q1
270 pF
HO
HS
LED
-12V
ADJ
EN
T
ON
ADJ
EN
0.47 mF
LM3434
BST
6 mH
0.01
LED CATHODE
DIM
DIM
V
CC
Q2
+3.3V
V
IN
LO
22 mF
4.7 mF
2.2 mF
GND
-12V
0.01
mF
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
2
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2010–2013, Texas Instruments Incorporated
LM3434
SNVS619B –MARCH 2010–REVISED MAY 2013
www.ti.com
CONNECTION DIAGRAM
1
2
3
4
5
6
18
17
16
15
14
13
HS
T
ON
ADJ
EN
HO
BST
LM3434
DIM
V
CC
LO
LS
V
IN
CGND
Figure 1. 24-Lead WQFN (Top View)
See RTW0024A Package
PIN DESCRIPTIONS
Pin
Name
Function
On-time programming pin. Tie an external resistor (RON) from TON to CSN, and a capacitor (CON) from TON to VEE
This sets the nominal operating frequency when the LED is fully illuminated.
.
1
TON
Analog LED current adjust. Tie to VIN for fixed 60mV average current sense resistor voltage. Tie to an external
reference to adjust the average current sense resistor voltage (programmed output current). Refer to the "VSENSE
vs. ADJ Voltage" graphs in the Typical Performance Characteristics section and the Design Procedure section of
the datasheet.
2
3
ADJ
EN
Enable pin. Connect this pin to logic level HI or VIN for normal operation. Connect this pin to CGND for low current
shutdown. EN is internally tied to VIN through a 100k resistor.
4
5
6
7
8
9
DIM
VIN
Logic level input for LED PWM dimming. DIM is internally tied to CGND through a 100k resistor.
Logic power input: Connect to positive voltage between +3.0V and +5.8V w.r.t. CGND.
Chassis ground connection.
CGND
VEE
Negative voltage power input: Connect to voltage between –30V to –9V w.r.t. CGND.
COMP
NC
Compensation pin. Connect a capacitor between this pin and VEE
.
No internal connection. Tie to VEE or leave open.
Soft Start pin. Tie a capacitor from SS to VEE to reduce input current ramp rate. Leave pin open if function is not
used. The SS pin is pulled to VEE when the device is not enabled.
10
SS
11
12
13
14
NC
NC
LS
No internal connection. Tie to VEE or leave open.
No internal connection. Tie to VEE or leave open.
Low side FET gate drive return pin.
LO
Low side FET gate drive output. Low in shutdown.
Low side FET gate drive power bypass connection and boost diode anode connection. Tie a 2.2µF capacitor
15
VCC
between VCC and VEE
.
16
17
18
19
20
BST
HO
High side "synchronous" FET drive bootstrap rail.
High side "synchronous" FET gate drive output. Pulled to HS in shutdown.
Switching node and high side "synchronous" FET gate drive return.
HS
DIMR
DIMO
LED dimming FET gate drive return. Tie to LED cathode. If PWM dimming is not used this pin may be left open.
LED dimming FET gate drive output. DIMO is a driver that switches between DIMR and BST2. If PWM dimming is
not used this pin may be left open.
21
22
BST2
NC
DIMO high side drive supply pin. Tie a 0.1µF between BST2 and CGND.
No internal connection. Tie to VEE or leave open.
2
Submit Documentation Feedback
Copyright © 2010–2013, Texas Instruments Incorporated
Product Folder Links: LM3434
LM3434
www.ti.com
SNVS619B –MARCH 2010–REVISED MAY 2013
PIN DESCRIPTIONS (continued)
Pin
23
Name
CSN
CSP
VEE
Function
Current sense amplifier inverting input. Connect to current sense resistor negative terminal.
Current sense amplifier non-inverting input. Connect to current sense resistor positive terminal.
Exposed Pad on the underside of the device. Connect this pad to a PC board plane connected to VEE
24
EP
.
BLOCK DIAGRAM
V
IN
CGND
BST2
Linear
Regulator
Level
Shift
DIM
PWM
Driver
DIMO
DIMR
Level
Shift
EN
ADJ
V
CC
UVLO
BST
HO
HS
-
Thermal
Shutdown
+
Gm
Bootstrap
Driver
CSP
CSN
+
-
Programmable
ON Time
Gm
Off-Time
Comp
Low Side
Gate
Driver
10 mA
LO
LS
SS
COMP
V
EE
T
ON
Copyright © 2010–2013, Texas Instruments Incorporated
Submit Documentation Feedback
3
Product Folder Links: LM3434
LM3434
SNVS619B –MARCH 2010–REVISED MAY 2013
www.ti.com
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
(1)
ABSOLUTE MAXIMUM RATINGS
If Military/Aerospace specified devices are required, contact the Texas Instruments Semiconductor Sales Office/
Distributors for availability and specifications.
VALUE / UNIT
VIN, EN, DIM, ADJ to CGND
COMP, SS to VEE
-0.3V to +7V
-0.3V to +7V
BST to HS
-0.3V to +7V
VCC to VEE
-0.3V to +7.5V
-0.3V to +33V
-0.3V to +33V
-0.3V to +0.3V
HS-0.3V to BST+0.3V
-0.3V to +7V
CGND, DIMR, CSP, CSN, TON to VEE
(2)
HS to VEE
LS to VEE
HO output
DIMO to DIMR
LO output
LS-0.3V to VCC +0.3V
-0.3V to 40V
BST2 to VEE
Maximum Junction Temperature
Power Dissipation(3)
ESD Susceptibility Human Body Model(4)
150°C
Internally Limited
2kV
(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 ensured. For ensured specifications and test
conditions, see the Electrical Characteristics.
(2) The HS pin can go to -6V with respect to VEE for 30ns and +22V with respect to VEE for 50ns without sustaining damage.
(3) The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(MAX), the junction-to-ambient thermal
resistance, θJA, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated
using: PD (MAX) = (TJ(MAX) − TA)/θJA. Exceeding the maximum allowable power dissipation will cause excessive die temperature, and
the regulator will go into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage. Thermal
shutdown engages at TJ=175°C (typ.) and disengages at TJ=155°C (typ).
(4) Human Body Model, applicable std. JESD22-A114-C.
RECOMMENDED OPERATING CONDITIONS
VALUE / UNIT
(1)
Operating Junction Temperature Range
Storage Temperature
−40°C to +125°C
−65°C to +150°C
3.0V to 5.8V
-9V to -30V
Input Voltage VIN w.r.t. CGND
Input Voltage VEE w.r.t. CGND
ADJ Input Voltage Range to CGND
0V to VIN
(1) All limits specified at room temperature (standard typeface) and at temperature extremes (bold typeface). All room temperature limits are
100% production tested. All limits at temperature extremes are ensured via correlation using standard Statistical Quality Control (SQC)
methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
4
Submit Documentation Feedback
Copyright © 2010–2013, Texas Instruments Incorporated
Product Folder Links: LM3434
LM3434
www.ti.com
SNVS619B –MARCH 2010–REVISED MAY 2013
ELECTRICAL CHARACTERISTICS
Specifications 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 specified 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: VEE = -12.0V and VIN = +3.3V with respect to CGND.
(1)
(2)
(1)
Symbol
Parameter
Conditions
Min
Typ
Max
Units
SUPPLY CURRENT
IINVEE
VEE Quiescent Current
EN = CGND
142
250
µA
EN = VIN, Not Switching
EN = VIN, Not Switching
EN = CGND
1.0
450
35
mA
IINVIN
VIN Quiescent Current
µA
71
OUTPUT CURRENT CONTROL
VCS
Current sense target voltage; VCS = VCSP
VCSN
–
VADJ = VIN
57
15
60
63
18
mV
V/V
GADJ
ICSN
IADJ Gain = (VADJ-CGND)/(VCNP-VCSN
)
VIN = 3.3V, VADJ = 0.5V or 1.5V
w.r.t. CGND
16.67
Isense Input Current
VADJ = 1V w.r.t. CGND
VADJ = VIN
-50
10
60
1
µA
ICSP
Gm
Isense Input Current
VADJ = VIN
µA
VADJ = 1V w.r.t. CGND
CS to COMP Transconductance;
Gm = ICOMP / (VCSP – VCSN - VADJ/16.67)
0.6
1.3
2.2
mS
ON TIME CONTROL
TONTH
On time threshold
VTON - VEE at terminate ON time
event
230
6.3
287
334
7.1
mV
GATE DRIVE AND INTERNAL REGULATOR
VCCOUT
VCCILIM
ROLH
VCC output regulation w.r.t. VEE
VCC current limit
ICC = 0mA to 20mA
VCC = VEE
6.75
-110
2
V
mA
HO output low resistance
HO output high resistance
LO output low resistance
LO output high resistance
DIMO output low resistance
DIMO output high resistance
I = 50mA source
I = 50mA sink
I = 50mA source
I = 50mA sink
I = 5mA source
I = 5mA sink
Ω
Ω
Ω
ROHH
ROLL
3
2
ROHL
3
ROLP
20
30
ROHP
FUNCTIONAL CONTROL
VINUVLO VIN undervoltage lockout
VCCUVLO VCC - VEE undervoltage lockout thresholds
With respect to CGND
On Threshold
1.4
6.6
5.4
V
V
6.0
4.9
7.0
5.8
1.6
Off threshold
VEN
Enable threshold, with respect to CGND
Device on w.r.t. CGND
Device off w.r.t. CGND
V
kΩ
V
0.6
REN
Enable pin pullup resistor
DIM logic input threshold
100
100
VDIM
DIM rising threshold w.r.t. CGND
DIM falling threshold w.r.t. CGND
1.6
0.6
RDIM
IADJ
ISS
DIM pin pulldown resistor
ADJ pin current
kΩ
µA
µA
kΩ
-1.0
1.0
SS pin source current
SS pin pulldown resistance
10
RSS
EN = CGND
1.0
(1) All limits specified at room temperature (standard typeface) and at temperature extremes (bold typeface). All room temperature limits are
100% production tested. All limits at temperature extremes are ensured via correlation using standard Statistical Quality Control (SQC)
methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
(2) Typical numbers are at 25°C and represent the most likely norm.
Copyright © 2010–2013, Texas Instruments Incorporated
Submit Documentation Feedback
5
Product Folder Links: LM3434
LM3434
SNVS619B –MARCH 2010–REVISED MAY 2013
www.ti.com
ELECTRICAL CHARACTERISTICS (continued)
Specifications 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 specified 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: VEE = -12.0V and VIN = +3.3V with respect to CGND.
(1)
(2)
(1)
Symbol
Parameter
Conditions
Min
Typ
Max
Units
AC SPECIFICATIONS
TDTD
LO and HO dead time
LO falling to HO rising dead time
HO falling to LO rising dead time
DIM rising to DIMO rising delay
DIM falling to DIMO falling delay
26
ns
ns
28
96
40
TPDIM
DIM to DIMO propagation delay
175
160
THERMAL SPECIFICATIONS
TJLIM
Junction temperature thermal limit
175
20
°C
°C
TJLIM(hyst)
θJA
Thermal limit hysteresis
WQFN package thermal resistance
JEDEC 4 layer board
39
°C/W
6
Submit Documentation Feedback
Copyright © 2010–2013, Texas Instruments Incorporated
Product Folder Links: LM3434
LM3434
www.ti.com
SNVS619B –MARCH 2010–REVISED MAY 2013
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs. LED Forward Voltage
(VCGND-VEE = 9V)
Efficiency vs. LED Forward Voltage
(VCGND-VEE = 12V)
97
96
95
94
93
92
91
90
89
88
87
96
94
92
90
88
86
84
2A
4A
6A
8A
2A
4A
6A
8A
1
2
3
4
5
6
7
1
2
3
4
5
6
7
V
(V)
LED
V
(V)
LED
Figure 2.
Figure 3.
Efficiency vs. LED Forward Voltage
(VCGND-VEE = 14V)
VSENSE vs. VADJ
(VIN = 3.3V)
96
94
92
90
88
86
84
82
80
100
2A
4A
6A
8A
90
80
70
60
50
40
30
20
10
0
0.2 0.4 0.6 0.8
1
1.2 1.4 1.6
1
2
3
4
5
6
7
ADJ VOLTAGE (V)
V
(V)
LED
Figure 4.
Figure 5.
VSENSE vs. VADJ
(VIN = 5.0V)
VSENSE vs. Temperature
(ADJ = VIN
)
61
60.8
60.6
60.4
60.2
60
250
200
150
100
50
59.8
59.6
59.4
59.2
59
0
0.2
-40
-20
0
20
40
60
80
0.7
1.2
1.7
2.2
2.7
3.2
AMBIENT TEMPERATURE
ADJ VOLTAGE (V)
Figure 6.
Figure 7.
Copyright © 2010–2013, Texas Instruments Incorporated
Submit Documentation Feedback
7
Product Folder Links: LM3434
LM3434
SNVS619B –MARCH 2010–REVISED MAY 2013
www.ti.com
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VSENSE vs. Temperature
(ADJ = 1.0V)
Average LED Current vs. DIM Duty Cycle
(30kHz dimming, ILED = 6A nominal)
61
60.8
60.6
60.4
60.2
60
7
6
5
4
3
2
1
0
59.8
59.6
59.4
59.2
59
-40
-20
0
20
40
60
80
0
10 20 30 40 50 60 70 80 90 100
AMBIENT TEMPERATURE
DIM DUTY CYCLE (%)
Figure 8.
Figure 9.
Startup Waveform
Shutdown Waveform
ILED = 6A nominal, VIN = 3.3V, VEE = -12V, VLED = 3V, SS = open
Top trace: EN input, 2V/div, DC
ILED = 6A nominal, VIN = 3.3V, VEE = -12V, VLED = 3V, SS = open
Top trace: EN input, 2V/div, DC
Middle trace: VEE input current, 2A/div, DC
Bottom trace: ILED, 2A/div, DC
Middle trace: VEE input current, 2A/div, DC
Bottom trace: ILED, 2A/div, DC
T = 100µs/div
T = 100µs/div
Figure 10.
Figure 11.
30kHz PWM Dimming Waveform
Showing Inductor Ripple Current
ILED = 6A nominal, VIN = 3.3V, VEE = -12V
Top trace: DIM input, 2V/div, DC
Bottom trace: ILED, 2A/div, DC
T = 10µs/div
Figure 12.
8
Submit Documentation Feedback
Copyright © 2010–2013, Texas Instruments Incorporated
Product Folder Links: LM3434
LM3434
www.ti.com
SNVS619B –MARCH 2010–REVISED MAY 2013
OPERATION
CURRENT REGULATOR OPERATION
The LM3434 is a controller for a Continuous Conduction Buck Converter. Because of its buck topology and
operation in the continuous mode, the output current is very well controlled. It only varies within a switching
frequency cycle by the inductor ripple current. This ripple current is normally set at 10% of the DC current.
Setting the ripple current lower than 10% is a useful tradeoff of inductor size for less LED light output ripple.
Additional circuitry can be added to achieve any LED light ripple desired.
The LED current is set by the voltage across a sense resistor. This sense voltage is nominally 60mV but can be
programmed higher or lower by an external control voltage.
The running frequency of the converter is programmed by an external RC network in conjunction with the LED's
forward voltage. The frequency is nominally set around 200kHz to 500khz. Fast PWM control is available by
shorting the output of the current source by a MOSFET in parallel with the LED. During the LED OFF time the
running frequency is determined by the RC network and the parasitic resistance of the output circuit including the
DIM FET RDSON
.
The LM3434 system has been evaluated to be a very accurate, high compliance current source. This is manifest
in its high output impedance and accurate current control. The current is measured to vary less than 6mA out of
6A when transitioning from LED OFF (output shorted) to LED ON (output ~6V).
PROTECTION
The LM3434 has dedicated protection circuitry running during normal operation. The thermal shutdown circuitry
turns off all power devices when the die temperature reaches excessive levels. The VCC undervoltage lockout
(UVLO) comparator protects the power devices during power supply startup and shutdown to prevent operation
at voltages less than the minimum operating input voltage. The VCC pin is short circuit protected to VEE. The
LM3434 also features a shutdown mode which decreases the supply current to approximately 35µA.
The ADJ, EN, and DIM pins are capable of sustaining up to +/-2mA. If the voltages on these pins will exceed
either VIN or CGND by necessity or by a potential fault, an external resistor is recommended for protection. Size
this resistor to limit pin current to under 2mA. A 10k resistor should be sufficient. This resistor may be used in
any application for added protection without any impact on function or performance.
Output Open Circuit
The LM3434 can be powered up with an open circuit without sustaining any damage to the circuit. During normal
operation the circuit will also tolerate an open circuit condition without sustaining damage provided a schottky
diode is placed within the circuit to provide a current path to disharge the energy stored in the inductor. The
anode of the schottky should be connected to the negative supply voltage while the cathode should be
connected to the point where the inductor and sense resistor intersect. This diode should have a surge current
rating equal to that of the maximum LED current driven.
DESIGN PROCEDURE
This section presents guidelines for selecting external components.
SETTING LED CURRENT CONTROL
LM3434 uses average current mode control to regulate the current delivered to the LED (ILED). An external
current sense resistor (RSENSE) in series with the LED is used to convert ILED into a voltage that is sensed by the
LM3434 at the CSP and CSN pins. CSP and CSN are the inputs to an error amplifier with a programmed input
offset voltage (VSENSE). VSENSE is used to regulate ILED based on the following equation:
ILED = VSENSE/RSENSE
(1)
Copyright © 2010–2013, Texas Instruments Incorporated
Submit Documentation Feedback
9
Product Folder Links: LM3434
LM3434
SNVS619B –MARCH 2010–REVISED MAY 2013
www.ti.com
FIXED LED CURRENT
The ADJ pin sets VSENSE. Tie ADJ to VIN to use a fixed 60mV internal reference for VSENSE. Select RSENSE to fix
the LED current based on the following equation:
RSENSE = 60mV/ILED
(2)
ADJUSTABLE LED CURRENT
When tied to an external voltage the ADJ pin sets VSENSE based on the following equation:
VSENSE = (VADJ - VCGND)/16.66
(3)
When the reference on ADJ is adjustable, VSENSE and ILED can be adjusted within the linear range of the ADJ pin.
This range has the following limitations:
0.3V < VADJ < (The greater of 1.5V or (VIN - 1.9V))
(4)
When VADJ is less than this linear range the VSENSE is specified by design to be less than or equal to
0.3V/16.667. When VADJ is greater than this linear range and less than VIN - 1V, VSENSE is specified by design to
be less than or equal to VADJ/16.667. If VADJ is greater than VIN - 1V, VSENSE switches to 60mV.
INPUT CAPACITOR SELECTION
A low ESR ceramic capacitor is needed to bypass the MOSFETs. This capacitor is connected between the drain
of the synchronous FET (CGND) and the source of the main switch (VEE). This capacitor prevents large voltage
transients from appearing at the VEE pin of the LM3434. Use a 22µF value minimum with X5R or X7R dielectric.
In addition to the FET bypass capacitors, additional bypass capacitors should be placed near the VEE and VIN
pins and should be returned to CGND.
The input capacitor must also be sized to handle the dimming frequency input ripple when the DIM function is
used. This ripple may be as high as 85% of the nominal DC input current (at 50% duty cycle). When dimming
this input capacitor should be selected to handle the input ripple current.
RECOMMENDED OPERATING FREQUENCY AND ON TIME "TIMEON" CALCULATION
Although the switching frequency can be set over a wide range, the following equation describes the
recommended frequency selection given inexpensive magnetic materials available today:
A
(MHz)
f =
ILED
(5)
In the above equation A=1.2 for powdered iron core inductors and A=0.9 or less for ferrite core inductors. This
difference takes into account the fact that ferrite cores generally become more lossy at higher frequencies. Given
the switching frequency f calculated above, TIMEON can be calculated. If VLED is the forward voltage drop of the
LED that is being driven, TIMEON can be calculated with the following equation:
VLED
TIMEON
=
f|V
|
EE
(6)
TIMING COMPONENTS (RON and CON)
Using the calculated value for TIMEON, the timing components RON and CON can be selected. CON should be
large enough to dominate the parasitic capacitance of the TON pin. A good CON value for most applications is
1nF. Based on calculated TIMEON, CON, and the nominal VEE and VLED voltages, RON can be calculated based on
the following equation:
TIMEON
CON(0.3/(|VEE|-VLED))
RON
=
(7)
10
Submit Documentation Feedback
Copyright © 2010–2013, Texas Instruments Incorporated
Product Folder Links: LM3434
LM3434
www.ti.com
SNVS619B –MARCH 2010–REVISED MAY 2013
INDUCTOR SELECTION
The most critical inductor parameters are inductance, current rating, and DC resistance. To calculate the
inductance, use the desired peak to peak LED ripple current (IRIPPLE), RON, and CON. A reasonable value for
IRIPPLE is 10% of ILED. The inductor value is calculated using the following equation:
0.3 x RON x CON
L =
IRIPPLE
(8)
For all VLED and VEE voltages, IRIPPLE remains constant and is only dependent on the passive external
components RON, CON, and L.
The I2R loss caused by the DC resistance of the inductor is an important parameter affecting the efficiency.
Lower DC resistance inductors are larger. A good tradeoff point between the efficiency and the core size is
letting the inductor I2R loss equal 1% to 2% of the output power. The inductor should have a current rating
greater than the peak current for the application. The peak current is ILED plus 1/2 IRIPPLE
.
POWER FET SELECTION
FETs should be chosen so that the I2RDSON loss is less than 1% of the total output power. Analysis shows best
efficiency with around 8mΩ of RDSON and 15nC of gate charge for a 6A application. All of the switching loss is in
the main switch FET. An additional important parameter for the synchronous FET is reverse recovery charge
(QRR). High QRR adversely affects the transient voltages seen by the IC. A low QRR FET should be used.
DIM FET SELECTION
Choose a DIM FET with the lowest RDSON for maximum efficieny and low input current draw during the DIM
cycle. The output voltage during DIM will determine the switching frequency. A lower output voltage results in a
lower switching frequency. If the lower frequency during DIM must be bound, choose a FET with a higher RDSON
to force the switching frequency higher during the DIM cycle.
Placement of the Parallel Dimming FET
When using a FET in parallel with the LED for PWM dimming special consideration must be used for the location
of the FET. The ideal placement of the FET is directly next to the LED. Any distance between this FET and the
LED results in line inductance. Fast current changes through this inductance can induce large voltage spikes due
to v = Ldi/dt. These can be mitigated by either reducing the distance between the FET and the LED and/or
slowing the PWM edges, and therefore the dt, by using some gate resistance on the FET. In cases where the
dimming FET is not placed close to the LED and/or very fast switching edges are desired the induced voltages
can become great enough to damage the dimming FET and/or the LM3434 HS pin. This can also result in a
large spike of current into the LED when the FET is turned off. In these cases a snubber should be placed across
the dimming FET to protect the device(s).
BOOTSTRAP CAPACITORS
The LM3434 uses two bootstrap capacitors and a bypass capacitor on VCC to generate the voltages needed to
drive the external FETs. A 2.2µF ceramic capacitor or larger is recommended between the VCC and LS pins. A
0.47µF is recommended between the HS and BST pins. A 0.1µF is recommended between BST2 and CGND.
SOFT-START CAPACITOR
The LM3434 integrates circuitry that, when used in conjunction with the SS pin, will slow the current ramp on
start-up. The SS pin is used to tailor the soft-start for a specific application. A capacitor value of 0.1µF on the SS
pin will yield a 12mS soft start time. For most applications soft start is not needed.
ENABLE OPERATION
The EN pin of the LM3434 is designed so that it may be controlled using a 1.6V or higher logic signal. If the
enable function is not used, the EN pin may be tied to VIN or left open. This pin is pulled to VIN internally through
a 100k pull up resistor.
Copyright © 2010–2013, Texas Instruments Incorporated
Submit Documentation Feedback
11
Product Folder Links: LM3434
LM3434
SNVS619B –MARCH 2010–REVISED MAY 2013
www.ti.com
PWM DIM OPERATION
The DIM pin of the LM3434 is designed so that it may be controlled using a 1.6V or higher logic signal. The
PWM frequency easily accomodates more than 40kHz dimming and can be much faster if needed. If the PWM
DIM pin is not used, tie it to CGND or leave it open. The DIM pin is tied to CGND internally through a 100k pull
down resistor.
LAYOUT CONSIDERATIONS
The LM3434 is a high performance current driver so attention to layout details is critical to obtain maximum
performance. The most important PCB board design consideration is minimizing the loop comprised by the main
FET, synchronous FET, and their associated decoupling capacitor(s). Place the VCC bypass capacitor as near as
possible to the LM3434. Place the PWM dimming/shunt FET as close to the LED as possible. A ground plane
should be used for power distribution to the power FETs. Use a star ground between the LM3434 circuitry, the
synchronous FET, and the decoupling capacitor(s). The EP contact on the underside of the package must be
connected to VEE. The two lines connecting the sense resistor to CSN and CSP must be routed as a differential
pair directly from the resistor. A Kelvin connection is recommended. It is good practice to route the DIMO/DIMR,
HS/HO, and LO/LS lines as differential pairs. The most important PCB board design consideration is minimizing
the loop comprised by the main FET, synchronous FET, and their associated decoupling capacitor(s). Optimally
this loop should be orthogonal to the ground plane.
12
Submit Documentation Feedback
Copyright © 2010–2013, Texas Instruments Incorporated
Product Folder Links: LM3434
LM3434
www.ti.com
SNVS619B –MARCH 2010–REVISED MAY 2013
APPLICATION INFORMATION
0.1
mF
LED ANODE
Q3*
44.2k
Q1
270 pF
HO
LED
-12V
T
ON
HS
ADJ
EN
ADJ
EN
0.47 mF
LM3434
BST
15 mH
22 mF
0.01
LED CATHODE
DIM
DIM
V
CC
LO
Q2
V
IN
+3.3V
100
4.7 mF
2.2 mF
* Only required if PWM dimming is used.
GND
-12V
0.01
mF
+
0.1
mF
68 mF*
Figure 13. Up to 10A Output Application Circuit
0.1
mF
LED ANODE
LED
39k
Q1
Q2
Q5* Q6*
330 pF
HO
HS
-12V
T
ON
ADJ
EN
ADJ
EN
0.47 mF
LM3434
BST
Q3
Q4
10 mH
0.005
LED CATHODE
DIM
DIM
V
CC
LO
V
IN
+5V
100
4.7 mF
22 mF X 2
GND
-12V
* Only required if PWM dimming is used.
0.01
mF
+
2.2 mF
0.1
mF
150 mF*
Figure 14. Up to 20A Output Application Circuit
Table 1. Some Recommended Inductors (Others May Be Used)
Manufacturer
Inductor
Contact Information
Coilcraft
GA3252-AL series, SER1360 series, and SER2900 series
www.coilcraft.com
800-322-2645
Coiltronics
Pulse
HCLP2 series
PB2020 series
www.coiltronics.com
www.pulseeng.com
Copyright © 2010–2013, Texas Instruments Incorporated
Submit Documentation Feedback
13
Product Folder Links: LM3434
LM3434
SNVS619B –MARCH 2010–REVISED MAY 2013
www.ti.com
Table 2. Some Recommended Input/Bypass Capacitors (Others May Be Used)
Manufacturer
Capacitor
Contact Information
Vishay Sprague
293D, 592D, and 595D series tantalum
www.vishay.com
407-324-4140
Taiyo Yuden
High capacitance MLCC ceramic
www.t-yuden.com
408-573-4150
ESRD seriec Polymer Aluminum Electrolytic
SPV and AFK series V-chip series
Cornell Dubilier
MuRata
www.cde.com
High capacitance MLCC ceramic
www.murata.com
Table 3. Some Recommended MOSFETs (Others May Be Used)
Manufacturer
MOSFET
Contact Information
Siliconix
Si7386DP (Main FET, DIM FET)
Si7668ADP (Synchronous FET)
www.vishay.com/company/bra
nds/siliconix/
Si7790DP (Main FET, Synchronous FET, DIM FET)
ON Semiconductor
NTMFS4841NHT1G (Main FET, Synchronous FET, DIM FET)
www.onsemi.com
14
Submit Documentation Feedback
Copyright © 2010–2013, Texas Instruments Incorporated
Product Folder Links: LM3434
LM3434
www.ti.com
SNVS619B –MARCH 2010–REVISED MAY 2013
REVISION HISTORY
Changes from Revision A (May 2013) to Revision B
Page
•
Changed layout of National Data Sheet to TI format .......................................................................................................... 14
Copyright © 2010–2013, Texas Instruments Incorporated
Submit Documentation Feedback
15
Product Folder Links: LM3434
PACKAGE OPTION ADDENDUM
www.ti.com
2-May-2013
PACKAGING INFORMATION
Orderable Device
LM3434SQ/NOPB
LM3434SQX/NOPB
Status Package Type Package Pins Package
Eco Plan Lead/Ball Finish
MSL Peak Temp
Op Temp (°C)
-40 to 125
Top-Side Markings
Samples
Drawing
Qty
(1)
(2)
(3)
(4)
ACTIVE
WQFN
WQFN
RTW
24
24
1000
Green (RoHS
& no Sb/Br)
CU SN
CU SN
Level-1-260C-UNLIM
L3434
L3434
ACTIVE
RTW
4500
Green (RoHS
& no Sb/Br)
Level-1-260C-UNLIM
-40 to 125
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
Multiple Top-Side Markings will be inside parentheses. Only one Top-Side Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a
continuation of the previous line and the two combined represent the entire Top-Side Marking for that device.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
8-May-2013
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
B0
K0
P1
W
Pin1
Diameter Width (mm) (mm) (mm) (mm) (mm) Quadrant
(mm) W1 (mm)
LM3434SQ/NOPB
LM3434SQX/NOPB
WQFN
WQFN
RTW
RTW
24
24
1000
4500
178.0
330.0
12.4
12.4
4.3
4.3
4.3
4.3
1.3
1.3
8.0
8.0
12.0
12.0
Q1
Q1
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
8-May-2013
*All dimensions are nominal
Device
Package Type Package Drawing Pins
SPQ
Length (mm) Width (mm) Height (mm)
LM3434SQ/NOPB
LM3434SQX/NOPB
WQFN
WQFN
RTW
RTW
24
24
1000
4500
210.0
367.0
185.0
367.0
35.0
35.0
Pack Materials-Page 2
MECHANICAL DATA
RTW0024A
SQA24A (Rev B)
www.ti.com
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other
changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest
issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and
complete. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of sale
supplied at the time of order acknowledgment.
TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s terms
and conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessary
to support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarily
performed.
TI assumes no liability for applications assistance or the design of Buyers’ products. Buyers are responsible for their products and
applications using TI components. To minimize the risks associated with Buyers’ products and applications, Buyers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or
other intellectual property right relating to any combination, machine, or process in which TI components or services are used. Information
published by TI regarding third-party products or services does not constitute a license 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 significant portions 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. TI is not responsible or liable for such altered
documentation. Information of third parties may be subject to additional restrictions.
Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service
voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice.
TI is not responsible or liable for any such statements.
Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirements
concerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or support
that may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which
anticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might cause
harm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the use
of any TI components in safety-critical applications.
In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI’s goal is to
help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and
requirements. Nonetheless, such components are subject to these terms.
No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the parties
have executed a special agreement specifically governing such use.
Only those TI components which TI has specifically designated as military grade or “enhanced plastic” are designed and intended for use in
military/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI components
which have not been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal and
regulatory requirements in connection with such use.
TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use of
non-designated products, TI will not be responsible for any failure to meet ISO/TS16949.
Products
Applications
Audio
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
Medical
Logic
Security
www.ti.com/security
Power Mgmt
Microcontrollers
RFID
power.ti.com
Space, Avionics and Defense
Video and Imaging
www.ti.com/space-avionics-defense
www.ti.com/video
microcontroller.ti.com
www.ti-rfid.com
www.ti.com/omap
OMAP Applications Processors
Wireless Connectivity
TI E2E Community
e2e.ti.com
www.ti.com/wirelessconnectivity
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2013, Texas Instruments Incorporated
相关型号：
©2020 ICPDF网 联系我们和版权申明