LTC3202EMS [Linear]
Low Noise, High Efficiency Charge Pump for White LEDs; 低噪声，高效率电荷泵白光LED
| 型号： | LTC3202EMS |
| 厂家： | 
Linear |
| 描述： | Low Noise, High Efficiency Charge Pump for White LEDs |
| 文件： | 总12页 (文件大小：251K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC3202
Low Noise, High Efficiency
Charge Pump for White LEDs
U
FEATURES
DESCRIPTIO
The LTC®3202 is a low noise, constant frequency charge
pump DC/DC converter that uses fractional conversion to
increaseefficiencyinwhiteLEDapplications. Thepart can
be used to produce a regulated voltage or current of up to
125mAfroma2.7Vto4.5Vinput.Lowexternalpartscount
(two flying capacitors and two small bypass capacitors at
VIN and VOUT) make the LTC3202 ideally suited for small,
battery-powered applications.
■
Low Noise Constant Frequency Operation
■
25% Less Input Current Than Doubler Charge Pump
■
High Output Current: Up To 125mA
■
Small Application Circuit
■
Regulated Output Voltage or Current
■
Automatic Soft-Start
■
VIN Range: 2.7V to 4.5V
■
No Inductors
■
1.5MHz Switching Frequency
Aninternal2-bitDACallowsLEDcurrenttobeadjustedfor
LED brightness control. The LTC3202 also has thermal
shutdown protection and can survive a continuous short-
circuit from VOUT to GND. Built-in soft-start circuitry
prevents excessive inrush current during start-up. High
switching frequency enables the use of small external
capacitors. A low current shutdown feature disconnects
the load from VIN and reduces quiescent current to less
than1µA.
■
ICC < 1µA in Shutdown
■
Available in 10-Pin MSOP and 3mm × 3mm
DFN Packages
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APPLICATIO S
■
White LED Backlighting
Programmable Boost Current Source
■
The LTC3202 is available in the 10-pin MSOP and 3mm ×
3mm DFN packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATIO
Programmable White LED Power Supply
C2
1µF
C3
1µF
Input and Output Ripple
V
IN
7
–
8
+
9
+
6
–
(AC COUPLED)
20mV/DIV
0mA TO 125mA
C1
D0
C1
C2 C2
TOTAL CURRENT
3
2
10
1
V
OUT
CURRENT
PROGRAMMING
D1
LTC3202
GND
4
V
V
IN
OUT
V
FB
IN
3V TO 4.5V
(AC COUPLED)
20mV/DIV
C1
C4
36Ω
1µF
36Ω
36Ω
36Ω
36Ω
36Ω
1µF
5, 11
3202 G09
V
C
OUT
= 3.6V
OUT
= 60mA
500ns/DIV
IN
IN
= C
= 1µF
C1, C2, C3, C4 = MURATA GRM 39X5R105K6.3 OR TAIYO YUDEN JMK107BJ105MA
I
3202 TA01
3202fa
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LTC3202
W W U W
ABSOLUTE AXI U RATI GS
(Note 1)
VIN, VOUT to GND ......................................... –0.3V to 6V
D0, D1 .............................................–0.3V to VIN + 0.3V
VOUT Short-Circuit Duration............................. Indefinite
IOUT (Note 2)....................................................... 150mA
Operating Temperature Range (Note 3) ...–40°C to 85°C
Storage Temperature Range ..................–65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
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W
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PACKAGE/ORDER I FOR ATIO
TOP VIEW
ORDER PART
ORDER PART
NUMBER
NUMBER
TOP VIEW
D1
FB
1
2
3
4
5
10 D0
+
+
–
–
D1
FB
OUT
1
2
3
4
5
10 D0
9
8
7
6
C2
C1
C1
C2
+
+
–
–
LTC3202EMS
LTC3202EDD
9
8
7
6
C2
C1
C1
C2
11
V
OUT
V
V
IN
V
IN
GND
SGND
MS PACKAGE
10-LEAD PLASTIC MSOP
MS PART MARKING
LTWL
DD PART MARKING
LABB
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
TJMAX = 150°C, θJA = 120°C/W
TJMAX = 150°C, θJA = 44°C/W, θJC = 3°C/W
EXPOSED PAD IS PGND (PIN 11) MUST BE
CONNECTED TO GROUND PLANE
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 3.3V unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Input Power Supply
V
Operating Voltage
Operating Current
●
●
●
2.7
4.5
5
V
mA
µA
IN
I
I
I
= 0mA, V
= 0V
OUT
= 3.6V, V = D0 = D1 = 4.5V
2.5
CC
OUT
OUT
IN
Shutdown Current
V
1
SHDN
Feedback Pin Set Points
0.2V Setting Feedback Voltage
0.4V Setting Feedback Voltage
0.6V Setting Feedback Voltage
D0 = 1, D1 = 0, I
D0 = 0, D1 = 1, I
D0 = 1, D1 = 1, I
= 0mA, V = 3.6V
●
●
●
●
188
380
570
–50
200
400
600
212
420
630
50
mV
mV
mV
nA
OUT
OUT
OUT
IN
= 0mA, V = 3.6V
IN
= 0mA, V = 3.6V
IN
I
V
= 0.8V
FB
FB
Charge Pump
R
Open Loop Output Impedance (1.5V – V )/I
V
= 3.3V, V
= 4.4V, V = 0
●
4.5
0.35
1.5
6
Ω
mV/mA
MHz
OL
IN
OUT OUT
IN
OUT
FB
V
Load Regulation (∆V /∆I
)
I
= 10mA to 90mA, ∆V /∆V
= 1
OUT
OUT OUT
OUT
FB
OUT
CLK Frequency
D0, D1
High Level Input Voltage (V )
●
●
●
●
1.3
V
V
IH
Low Level Input Voltage (V )
0.4
1
IL
Input Current (I )
DO, D1 = V
–1
–1
µA
µA
IH
IN
Input Current (I )
DO, D1 = 0V
1
IL
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: Based on long-term current density limitations.
Note 3: The LTC3202E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
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LTC3202
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TYPICAL PERFOR A CE CHARACTERISTICS
V
FB Set Point vs Input Supply
VFB Set Point vs Input Supply
(200mV Setting)
(400mV Setting)
0.21
0.42
0.40
0.38
I
V
V
= 20µA
LOAD
D0
D1
I
V
V
= 40µA
LOAD
D0
D1
= V
IN
= 0V
= 0V
= V
IN
T
= 25°C
A
T
= 85°C
A
T
= 25°C
A
T
= 85°C
A
0.20
0.19
T
= –40°C
A
T
= –40°C
A
2.7
3.0
3.3
3.6
3.9
4.2
4.5
2.7
3.0
3.3
3.6
3.9
4.2
4.5
INPUT SUPPLY (V)
INPUT SUPPLY (V)
3202 G01
3202 G02
VFB Set Point vs Input Supply
(600mV Setting)
VFB vs Load Current
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.63
0.60
0.57
V
C
V
= V = V
D1 IN
D0
IN
I
= 60µA
LOAD
D0
= C
= C
= C
= 1µF
OUT
FB
= 25°C
FLY1
FLY2
V
= V = V
D1 IN
– V = 3.4V
OUT
T
A
V
IN
= 3.2V
T
= 25°C, 85°C
A
V
IN
= 3V
T
= –40°C
A
2.7
3.0
3.3
3.6
3.9
4.2
4.5
0
50
75
100
125
150
25
INPUT SUPPLY (V)
LOAD CURRENT (mA)
3202 G04
3202 G03
Oscillator Frequency vs Supply
Voltage
Input Current vs Load Current
1.9
1.7
1.5
1.3
1.1
0.9
160
140
120
100
80
V
C
A
= 3.6V
OUT
= 25°C
IN
IN
= C
= C
= C = 1µF
FLY2
FLY1
T
T
= –40°C
A
T
= 25°C
V
= 4.5V
V
A
OUT
= 4V
T
A
= 85°C
OUT
60
40
20
0
2.7
3.0
3.3
3.6
3.9
4.2
4.5
20
40
80
0
100
60
SUPPLY VOLTAGE (V)
LOAD CURRENT (mA)
3202 G06
3202 G05
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LTC3202
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TYPICAL PERFOR A CE CHARACTERISTICS
Short-Circuit Current vs Supply
Voltage
300
C
V
V
= 1µF
FLY
FB
= 0V
280
260
240
220
200
180
= 0V
OUT
T
= 25°C
A
2.7
3.3
3.6
3.9
4.2
4.5
3.0
INPUT SUPPLY (V)
3202 G07
VOUT Soft-Start Ramp
Input and Output Ripple
V
IN
(AC COUPLED)
20mV/DIV
V
D0, D1
2V/DIV
V
OUT
1V/DIV
V
OUT
(AC COUPLED)
20mV/DIV
3202 G08
3202 G09
V
C
= 3.6V
OUT
200µs/DIV
V
C
OUT
= 3.6V
OUT
= 60mA
500ns/DIV
IN
IN
IN
= 1µF
= C
= 1µF
I
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PI FU CTIO S
D1, D0 (Pin 1, 10): Control Inputs. D0 and D1 determine
GND (Pin 5): Ground for the Charge Pump and Control
Circuitry. This pin should be connected directly to a low
impedance ground plane.
C2–, C1–, C1+, C2+ (Pin 6, 7, 8, 9): Charge Pump Flying
Capacitor Pins. A 1µF X5R or X7R ceramic capacitor
should be connected from C1+ to C1– and from C2+ to
C2–.
the set point voltage of the FB pin (see Table 1).
FB (Pin 2): FB is the Feedback Input for the Regulation
Control Loop.
VOUT (Pin3):VOUT istheOutputoftheChargePump.Alow
impedance 1µF X5R or X7R ceramic capacitor is required
from VOUT to GND.
PGND (Pin 11, Exposed Pad DFN Only): Power Ground
for the Charge Pump. This pin must be connected directly
to a low impedance ground plane.
VIN (Pin 4): Input Supply Voltage. VIN should be bypassed
with a 1µF to 4.7µF low impedance ceramic capacitor.
3202fa
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LTC3202
W
W
SI PLIFIED BLOCK DIAGRA
2
FB
–
+
D0
D1
10
1
2-BIT
DAC
SOFT-START AND
SHUTDOWN
CONTROL
1.5MHz
OSCILLATOR
+
8
7
9
6
C1
V
4
3
IN
–
C1
V
OUT
+
–
C2
C2
3202 BD
5, 11 GND
3202fa
5
LTC3202
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OPERATIO
(Refer to Simplified Block Diagram)
The LTC3202 uses a fractional conversion switched ca- conditions it will automatically limit its output current to
pacitorchargepumptoboostVOUT toasmuchas1.5times approximately 250mA. At higher temperatures, or if the
the input voltage. A two-phase nonoverlapping clock acti- input voltage is high enough to cause excessive self
vates the charge pump switches. On the first phase of the heating on-chip, thermal shutdown circuitry will
clock the flying capacitors are charged in series from VIN. shut down the charge pump when the junction tempera-
On the second phase of the clock they are connected in ture exceeds approximately 160°C. It will reenable the
parallel and stacked on top of VIN. This sequence of charge pump once the junction temperature drops back to
charging and discharging the flying capacitors continues approximately155°C. TheLTC3202willcycleinandoutof
at a free running frequency of 1.5MHz (typ).
thermal shutdown indefinitely without latchup or damage
until the short-circuit on VOUT is removed.
Regulation is achieved by sensing the voltage at the FB pin
and modulating the charge pump strength based on the
error signal. The control pins, D0 and D1, program the set
point of the internal digital-to-analog converter. The regu-
lation loop will increase VOUT until FB comes to balance at
the set-point voltage. Table 1 shows the regulation voltage
as a function of D0 and D1.
Soft-Start
To prevent excessive current flow at VIN during start-up,
the LTC3202 has built-in soft-start circuitry. Soft-start is
achieved by increasing the amount of current available to
the output charge storage capacitor linearly over a period
of approximately 500µs.
Table 1. Feedback Control Voltage Settings
Thesoft-startfeatureactivatesanytimeaninput,D0orD1,
changes state. This will prevent large inrush current
during initial start-up as well as when the feedback setting
is changed from one value to the next. Note that the set
point voltage will drop to zero during the soft-start period.
Under heavy load conditions there may be observable
droop at VOUT until the soft-start circuit catches up.
D1
0
D0
0
Feedback Set Point Voltage
Shutdown
0.2V
0
1
1
0
0.4V
1
1
0.6V
In shutdown mode all circuitry is turned off and the
LTC3202 draws only leakage current from the VIN supply.
Furthermore, VOUT is disconnected from VIN. The D0 and
D1 pins are CMOS inputs with a threshold voltage of
approximately 0.8V. The LTC3202 is in shutdown when a
logiclowisappliedtobothD0andD1. SincetheD0andD1
pins are high impedance CMOS inputs they should never
be allowed to float. To ensure that their states are defined
they must always be driven with valid logic levels.
Programming the LTC3202 for Voltage or Current
The LTC3202 can be configured to control either a voltage
or a current. In white LED applications the LED current is
programmed by the ratio of the feedback set point voltage
and a sense resistor as shown in Figure 1. The current of
the remaining LEDs is controlled by virtue of their similar-
ity to the reference LED and the ballast voltage across the
sense resistor.
Shutdown Current
V
R
FB
I
=
LED
X
3
Output voltage detection circuitry will draw a current of
5µAwhentheLTC3202isinshutdown. Thiscurrentwillbe
eliminated when the output voltage (VOUT) is at 0V. To
ensure that VOUT is at 0V in shutdown a bleed resistor can
be used from VOUT to GND. 10k to 100k is acceptable.
V
OUT
LTC3202
2
• • •
FB
GND
5, 11
R
R
X
1µF
X
Short-Circuit/Thermal Protection
3202 F01
The LTC3202 has built-in short-circuit current limiting as
well as over temperature protection. During short-circuit
Figure 1. Current Control Mode
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LTC3202
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OPERATIO
(Refer to Simplified Block Diagram)
Inthisconfigurationthefeedbackfactor(∆VFB/∆VOUT)will
be very near unity since the small signal LED impedance
will be considerably less than the current setting resistor
RX. Thus, thisconfigurationwillhavethehighestloopgain
giving it the lowest closed-loop output resistance. Like-
wise it will also require the largest amount of output
capacitance to preserve stability.
Charge Pump Strength
Figure 3 shows how the LTC3202 can be modeled as a
Thevenin equivalent circuit to determine the amount of
current available from the effective input voltage, 1.5VIN
and the effective open-loop output resistance, ROL.
R
For fixed voltage applications, the output voltage can be
set by the ratio of two resistors and the feedback control
voltage as shown in Figure 2. The output voltage is given
by the set point voltage times the gain factor 1 + R1/R2.
Notethattheclosed-loopoutputresistancewillincreasein
proportion to the loop gain consumed by the resistive
divider ratio. For example, if the resistor ratio is 2:1 giving
a gain of 3, the closed-loop output resistance will be about
3 times higher than its nominal gain of 1 value. Given that
the closed-loop output resistance is about 0.35Ω with a
gain of 1, the closed-loop output resistance will be about
1Ω when using a gain of 3.
OL
+
+
1.5V
V
IN
OUT
–
–
3202 F03
Figure 3. Equivalent Open-Loop Circuit
From Figure 3 the available current is given by:
1.5VIN – VOUT
IOUT
=
ROL
R1
R2
V
= V (1 +
FB
)
Typical values of ROL as a function of temperature are
shown in Figure 4.
OUT
3
2
V
OUT
LTC3202
R1
R2
4.8
FB
V
L
= 0
FB
GND
5, 11
I
= 100mA
1µF
C1 = C2 = 1µF
4.6
4.4
4.2
4.0
3.8
R
= (1.5V – V )/I
OL
IN
OUT
L
3202 F02
Figure 2. Voltage Control Mode
V
= 2.7V
IN
V
= 3.6V
IN
When using the LTC3202 in voltage control mode, any of
the three voltage settings (0.2V, 0.4V or 0.6V) can be used
as the set point voltage. For optimum noise performance
and lowest closed-loop output resistance the highest
voltage setting will likely be the most desirable.
–40
–15
10
35
60
85
TEMPERATURE (°C)
3202 F04
Typical values for total voltage divider resistance can
range from several kΩs up to 1MΩ.
Figure 4. Typical ROL vs Temperature
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LTC3202
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OPERATIO
ROL is dependent on a number of factors including the
switching term, 1/(2fOSC CFLY), internal switch resis-
tances and the nonoverlap period of the switching circuit.
in the block diagram, the LTC3202 uses a control loop to
adjust the strength of the charge pump to match the
current required at the output. The error signal of this loop
is stored directly on the output charge storage capacitor.
The charge storage capacitor also serves to form the
dominant pole for the control loop. To prevent ringing or
instability, it is important for the output capacitor to
maintain at least 0.6µF of capacitance over all conditions.
However, for a given ROL, the amount of current available
will be directly proportional to the advantage voltage
1.5VIN – VOUT. This voltage can typically be quite small.
Consider the example of driving white LEDs from a
3.1V supply. If the LED forward voltage is 3.8V and the
0.6V VFB setting is used, the advantage voltage is 3.1V •
1.5V – 3.8V – 0.6V or only 250mV. However if the input
voltage is raised to 3.2V the advantage voltage jumps to
400mV—a 60% improvement in available strength! Note
that a similar improvement in advantage voltage can be
achieved by operating the LTC3202 at a lower voltage
setting such as the 0.4V setting.
Likewise, excessive ESR on the output capacitor will tend
to degrade the loop stability of the LTC3202. The closed-
loop output resistance of the LTC3202 is designed to be
0.35Ω. For a 100mA load current change, the feedback
voltage will change by about 35mV. If the output capacitor
has 0.35Ω or more of ESR the closed-loop frequency
response will cease to roll-off in a simple one-pole fashion
and poor load transient response or instability could
result. Multilayer ceramic chip capacitors typically have
exceptional ESR performance and combined with a tight
board layout should yield very good stability and load
transient performance.
VIN, VOUT Capacitor Selection
The style and value of capacitors used with the LTC3202
determineseveralimportantparameterssuchasregulator
control loop stability, output ripple, charge pump strength
and minimum start-up time.
As the value of COUT controls the amount of output ripple,
thevalueofCIN controlstheamountofripplepresentatthe
input pin (VIN). The input current to the LTC3202 will be
relatively constant while the charge pump is on either the
inputchargingphaseortheoutputchargingphasebutwill
drop to zero during the clock nonoverlap times. Since the
nonoverlaptimeissmall(~25ns)thesemissing“notches”
will result in only a small perturbation on the input power
supply line. Note that a higher ESR capacitor such as
tantalum will have higher input noise due to the input
current change times the ESR. Therefore ceramic capaci-
tors are again recommended for their exceptional ESR
performance.
To reduce noise and ripple, it is recommended that low
equivalent series resistance (ESR) ceramic capacitors be
used for both CIN and COUT. Tantalum and aluminum
capacitorsarenotrecommendedbecauseoftheirhigh ESR.
The value of COUT directly controls the amount of output
ripple for a given load current. Increasing the size of COUT
will reduce the output ripple at the expense of higher
minimum turn-on time and higher start-up current. The
peak-to-peak output ripple is approximately given by the
expression:
IOUT
3fOSC •COUT
VRIPPLEP−P
Furtherinputnoisereductioncanbeachievedbypowering
the LTC3202 through a very small series inductor as
shown in Figure 5. A 10nH inductor will reject the fast
current notches, thereby presenting a nearly constant
current load to the input power supply. For economy the
10nH inductor can be fabricated on the PC board with
about 1cm (0.4") of PC board trace.
Where fOSC is the LTC3202’s oscillator frequency (typi-
cally 1.5MHz) and COUT is the output charge storage
capacitor.
Both the style and value of the output capacitor can
significantly affect the stability of the LTC3202. As shown
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LTC3202
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OPERATIO
10nH
Table 2 Recommended Capacitor Vendors
4
V
IN
AVX
Kemet
www.avxcorp.com
www.kemet.com
V
IN
LTC3202
GND
0.1µF
1µF
5, 11
Murata
www.murata.com
www.t-yuden.com
www.vishay.com
Taiyo Yuden
Vishay
3202 F05
Figure 5. 10nH Inductor Used for Input Noise Reduction
For very light load applications the flying capacitor may be
reduced to save space or cost. The theoretical minimum
output resistance of a 2:3 fractional charge pump is given
by:
Flying Capacitor Selection
Warning: A polarized capacitor such as tantalum or alumi-
num should never be used for the flying capacitors since
their voltage can reverse upon start-up of the LTC3202.
Ceramic capacitors should always be used for the flying
capacitors.
1.5VIN – VOUT
IOUT
1
ROL(MIN)
≡
=
2f0SC FLY
C
Where fOSC is the switching frequency (1.5MHz typ) and
CFLY is the value of the flying capacitors. Note that the
charge pump will typically be weaker than the theoretical
limit due to additional switch resistance, however for very
light load applications the above expression can be used
as a guideline in determining a starting capacitor value.
The flying capacitor controls the strength of the charge
pump. In order to achieve the rated output current it is
necessary to have at least 0.7µF of capacitance for each of
the flying capacitors.
Capacitors of different materials lose their capacitance
with higher temperature and voltage at different rates. For
example, a ceramic capacitor made of X7R material will
retainmostofitscapacitancefrom–40°Cto85°Cwhereas
a Z5U or Y5V style capacitor will lose considerable capaci-
tance over that range. Z5U and Y5V capacitors may also
have a very poor voltage coefficient causing them to lose
60% or more of their capacitance when the rated voltage
is applied. Therefore, when comparing different capaci-
tors it is often more appropriate to compare the amount of
achievable capacitance for a given case size rather than
comparing the specified capacitance value. For example,
overratedvoltageandtemperatureconditions,a1µF,10V,
Y5V ceramic capacitor in a 0603 case may not provide any
more capacitance than a 0.22µF, 10V, X7R available in the
same 0603 case. The capacitor manufacturer’s data sheet
should be consulted to determine what value of capacitor
isneededtoensureminimumcapacitancesatalltempera-
tures and voltages.
Power Efficiency
The power efficiency (η) of the LTC3202 is similar to that
of a linear regulator with an effective input voltage of 1.5
times the actual input voltage. This occurs because the
input current for a 2:3 fractional charge pump is approxi-
mately1.5timestheloadcurrent.Inanidealregulating2:3
charge pump the power efficiency would be given by:
POUT VOUT •IOUT
VOUT
1.5VIN
ηIDEAL
≡
=
=
3
VIN • IOUT
2
P
IN
At moderate to high output power the switching losses
and quiescent current of the LTC3202 are negligible and
theexpressionaboveisvalid. ForexamplewithVIN =3.2V,
IOUT = 80mA and VOUT regulating to 4.2V the measured
efficiencyis82%whichisjustunderthetheoretical87.5%
calculation.
Table 2 shows a list of ceramic capacitor manufacturers
and how to contact them:
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LTC3202
U
OPERATIO
Layout Considerations
Thermal Management
Due to its high switching frequency and the transient
currentsproducedbytheLTC3202, carefulboardlayoutis
necessary. A true ground plane and short connections to
allcapacitorswillimproveperformanceandensureproper
regulationunderallconditions.Figure6showstherecom-
mended layout configurations.
The flying capacitor pins C1+, C2+, C1– and C2– will have
very high edge rate waveforms. The large dv/dt on these
pins can couple energy capacitively to adjacent printed
circuit board runs. Magnetic fields can also be generated
if the flying capacitors are not close to the LTC3202 (i.e.
the loop area is large). To decouple capacitive energy
transfer, a Faraday shield may be used. This is a grounded
PC trace between the sensitive node and the LTC3202
pins. For a high quality AC ground it should be returned to
a solid ground plane that extends all the way to the
LTC3202.
For higher input voltages and maximum output current
therecanbesubstantialpowerdissipationintheLTC3202.
If the junction temperature increases above approxi-
mately 160°C the thermal shutdown circuitry will auto-
matically deactivate the output. To reduce the maximum
junction temperature, a good thermal connection to the
PC board is recommended. Connecting the GND pin (Pin
5 and Pin 11 on the DFN package) to a ground plane, and
maintaining a solid ground plane under the device can
reduce the thermal resistance of the package and PC
board considerably.
Brightness Control Using Pulse Width Modulation
An alternative approach to dimming is to use pulse width
modulation rather than the internal digital to analog con-
verter. By connecting both the D0 and D1 pins to a PWM
signal, continuous brightness control can be achieved.
Frequencies from 100Hz to 500Hz are acceptable with a
1µF to 4.7µF output capacitor.
V
OUT
10
D0
GND
LTC3202
V
1
D0, D1
D1
V
IN
t
D1
D0
3202 F07
Figure 7. Alternative Brightness Control
V
OUT
V
IN
GND
3202 F06
Figure 6. Recommended Layouts
3202fa
10
LTC3202
U
PACKAGE DESCRIPTIO
MS Package
10-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1661)
3.00 ± 0.102
(.118 ± .004)
(NOTE 3)
0.889 ± 0.127
(.035 ± .005)
0.497 ± 0.076
(.0196 ± .003)
REF
10 9
8
7 6
5.23
3.20 – 3.45
(.206)
(.126 – .136)
MIN
3.00 ± 0.102
(.118 ± .004)
(NOTE 4)
4.90 ± 0.152
(.193 ± .006)
DETAIL “A”
0.254
(.010)
0° – 6° TYP
0.50
(.0197)
BSC
0.305 ± 0.038
(.0120 ± .0015)
TYP
GAUGE PLANE
1
2
3
4 5
RECOMMENDED SOLDER PAD LAYOUT
0.53 ± 0.152
(.021 ± .006)
0.86
(.034)
REF
1.10
(.043)
MAX
DETAIL “A”
0.18
(.007)
SEATING
PLANE
NOTE:
0.17 – 0.27
(.007 – .011)
TYP
0.127 ± 0.076
(.005 ± .003)
MSOP (MS) 0603
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
0.50
(.0197)
BSC
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1699)
R = 0.115
TYP
6
0.38 ± 0.10
10
0.55 ±0.05
3.35 ±0.05
1.65 ±0.05
3.00 ±0.10
(4 SIDES)
1.65 ± 0.10
(2 SIDES)
2.25 ±0.05 (2 SIDES)
PIN 1
TOP MARK
PACKAGE
OUTLINE
(DD10) DFN 0103
5
1
0.25 ± 0.05
0.50 BSC
0.75 ±0.05
0.200 REF
0.25 ± 0.05
0.50
BSC
2.38 ±0.10
(2 SIDES)
2.38 ±0.05
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2)
2. ALL DIMENSIONS ARE IN MILLIMETERS
3. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
4. EXPOSED PAD SHALL BE SOLDER PLATED
3202fa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
11
LTC3202
U
TYPICAL APPLICATIO
LED Driver with Linear Brightness Control
C2
1µF
C3
1µF
V
= 0V TO 3V
C
V
36Ω
R1 0.6V
)
R1
R2
C
7
–
8
+
9
+
6
–
I
= 1 +
(
–
•
LED
R2
R2 36Ω
C1
C1
C2 C2
3.9k
3
2
10
1
D0
OFF
ON
V
OUT
D1
LTC3202
GND
R1
1k
4
V
IN
V
FB
IN
3V TO 4.5V
C1
1µF
C4
1µF
36Ω
36Ω
36Ω
36Ω
36Ω
36Ω
5, 11
3202 TA02
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3202fa
LT/TP 0803 1K • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
12
●
●
LINEAR TECHNOLOGY CORPORATION 2001
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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