LT3596
1
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Typical applicaTion
FeaTures DescripTion
60V Step-Down LED Driver
The LT
®
3596 is a 60V step-down LED Driver. It achieves
10,000:1 digital PWM dimming at 100Hz with fast NPN
current sources driving up to 10 LEDs in each channel.
100:1 LED dimming can also be done with analog control
of the CTRL1-3 pin.
The step-down switching frequency is programmable
between 200kHz and 1MHz and is synchronizable to an
external clock. The LT3596 also provides maximum LED
brightness while adhering to manufacturers’ specifica-
tions for thermal derating. The derate temperature is
programmed by placing a negative temperature coefficient
(NTC) resistor on the master control pin.
The LT3596 adaptively controls VOUT in order to achieve
optimal efficiency. Other features include: 1.5% LED current
matching between channels, open LED reporting, shorted
LED pin protection and reporting, programmable LED cur-
rent and programmable temperature protection.
48V 1MHz Step-Down 8W, 100mA LED Driver (Eight White LEDs per Channel)
applicaTions
n 300mA Buck Regulator, Drives Up to 10 LEDs per
Channel with Fast NPN Current Sources
n Fast Current Sources for <1µs Pulse Widths
(10,000:1 True Color PWM™ Dimming at 100Hz)
n LEDs Disconnected in Shutdown
n Adaptive VOUT for Increased Efficiency
n 6V to 60V Input Voltage Range
n ±1.5% Accurate LED Current Matching
n External Resistors Set LED Current for Each Channel
n Requires No External Compensation
n Programmable Switching Frequency (200kHz to 1MHz)
n Synchronizable to External Clock
n Open, Short LED Detection and Reporting
n Programmable LED Thermal Derating and Reporting
n Programmable Temperature Protection
n 5mm × 8mm Thermally Enhanced QFN Package with
0.6mm High Voltage Pin Spacing
n LED Billboards and Signboards
n Mono, Multi, Full Color LED Displays
n Large Screen Display LED Backlighting
n Automotive, Industrial and Medical Displays
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation and True Color PWM is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
VIN
EN/UVLO
LT3596
SYNCSYNC
PWM1
PWM2
PWM3
PWM1
PWM2
PWM3
CTRL1
CTRL2
CTRL3
CTRL1
CTRL2
CTRL3
RT
FAULTFAULT
BIAS
270k
10µF
VIN
48V
91k
33.2k
VREF
TSET
CTRLM
10k
90.9k
49.9k 20k 20k 20k
3696 TA01a
100k
100k
BIAS
BOOST
SW
DA
GND
FB
LED1
LED2
LED3
ISET1
ISET2
ISET3
VOUT
4.7µF
5V
BIAS
z28V
PER LED
STRING
4.7µF
VOUT
100nF
100k
3.65k
100µH
10,000:1 PWM Dimming at 100Hz
PWM
2V/DIV
ILED
50mA/DIV
200ns/DIV 3596 TA01b
LT3596
2
3596fa
pin conFiguraTionabsoluTe MaxiMuM raTings
Input Voltage (VIN), EN/UVLO ..................................60V
BOOST .....................................................................80V
BOOST Pin Above SW Pin ....................................... 25V
LED1-3, VOUT ............................................................42V
BIAS, FAULT .............................................................25V
VREF, RT, ISET1-3, TSET, CTRLM .................................3V
FB, CTRL1-3, PWM1-3, SYNC ....................................6V
Operating Temperature Range
(Notes 2, 3) ............................................ –40°C to 125°C
Maximum Junction Temperature .......................... 125°C
Storage Temperature Range .................. –65°C to 150°C
(Note 1)
18 19 20
TOP VIEW
53
GND
UHG PACKAGE
VARIATION: UHG52 (39)
52-LEAD (5mm s 8mm) PLASTIC QFN
21 22 23 24 25 26
51 50 48 46 44
33
34
35
37
39
7
6
4
2
FB
EN/UVLO
TSET
VREF
GND
NC
NC
CTRLM
ISET1
ISET2
ISET3
RT
NC
NC
NC
BIAS
NC
NC
CTRL1
CTRL2
CTRL3
PWM1
PWM2
PWM3
SYNC
VIN
VIN
SW
BOOST
DA
NC
VOUT
LED1
LED2
NC
NC
LED3
FAULT
NC
32
31
30
29
28
27
9
11
12
13
14
15
16
17
41
43
TJMAX = 125°C, θJA = 32°C/W
EXPOSED PAD (PIN 53) IS GND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3596EUHG#PBF LT3596EUHG#TRPBF 3596 52-Lead (5mm × 8mm) Plastic QFN –40°C to 125°C
LT3596IUHG#PBF LT3596IUHG#TRPBF 3596 52-Lead (5mm × 8mm) Plastic QFN –40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
LT3596
3
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elecTrical characTerisTics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 24V, BOOST = 30V, BIAS = 5V, EN/UVLO = 5V, PWM1-3 = 3.3V,
CTRL1-3 = CTRLM = TSET = 2V, VOUT = 24V, SYNC = 0V unless otherwise specified. (Note 2)
PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN Operating Voltage l6 55 V
Quiescent Current from VIN EN/UVLO = 0.4V
BIAS = 5V, Not Switching
BIAS = 0V, Not Switching
1.3
3
2
4
5
µA
mA
mA
Minimum BIAS Voltage 3 3.1 V
Quiescent Current from BIAS EN/UVLO = 0.4V
BIAS = 5V, Not Switching
BIAS = 0V, Not Switching, Current Out of Pin
1.4
70
2
3
150
µA
mA
µA
EN Threshold 0.4 0.7 V
UVLO Threshold (Falling) 1.47 1.51 1.53 V
EN/UVLO Pin Current (Hysteresis) EN/UVLO = 1.6V
EN/UVLO = 1.4V
4.25
10
5.1
5.75
nA
µA
FB Regulation Voltage 1.15 1.21 1.25 V
FB Pin Bias Current FB = 6V 200 nA
Maximum Duty Cycle RT = 220k (200kHz)
RT = 33.2k (1MHz)
90
80
99
90
%
%
Switch Saturation Voltage ISW = 300mA 330 mV
Switch Current Limit 0.8 1.0 1.25 A
DA Pin Current to Stop OSC 500 650 750 mA
Switch Leakage VSW = 0V 700 nA
BOOST Pin Current ISW = 100mA 3 mA
Switching Frequency RT = 220k
RT = 33.2k
170
900
200
1000
230
1100
kHz
kHz
SYNC Input Low 0.4 V
SYNC Input High 1.6 V
SYNC Frequency Range RT = 220k
RT = 47k
240
1000
kHz
kHz
SYNC Pin Bias Current VSYNC = 3.3V 200 nA
Soft-Start Time (Note 4) 2.2 ms
VREF Voltage IVREF = 0µA l1.96 2.0 2.04 V
Maximum VREF Current 200 µA
ISET1-3 Pin Voltage RISET1-3 = 20k 1.0 V
TSET Voltage for LED Current Derating 540 mV
TSET Pin Leakage Current VTSET = 1V 200 nA
ILED1-3 LED Current RISET1-3 = 20k
l
98
97
100
100
102
103
mA
mA
LED String Current Matching RISET1-3 = 20k
l
±0.35
±0.35
±1.5
±2
%
%
LED Pin Voltage Adaptive VOUT Loop Enabled 1.07 V
LED1-3 Open Detection Threshold 0.29 V
LED1-3 Short Protection Threshold (from GND) 10 15 V
LED1-3 Short Protection Threshold (from VOUT) VOUT = 6V, VOUT > VLED1-3 1 1.2 1.6 V
LED1-3 Pin Leakage Current VLED1-3 = 42V, PWM1-3 = 0V 200 nA
LT3596
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PARAMETER CONDITIONS MIN TYP MAX UNITS
PWM1-3 Input Low Voltage 0.4 V
PWM1-3 Input High Voltage 1.6 V
PWM1-3 Pin Bias Current 200 nA
CTRL1-3 Voltage for Full LED Current 1.2 V
CTRL1-3 Pin Bias Current VCTRL1-3 = 6V 200 nA
CTRLM Voltage for Full LED Current 1.2 V
CTRLM Pin Bias Current VCTRLM = 3V 200 nA
FAULT Output Voltage Low IFAULT = 200µA 0.10 V
FAULT Pin Input Leakage Current VFAULT = 25V 200 nA
elecTrical characTerisTics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 24V, BOOST = 30V, BIAS = 5V, EN/UVLO = 5V, PWM1-3 = 3.3V,
CTRL1-3 = CTRLM = TSET = 2V, VOUT = 24V, SYNC = 0V unless otherwise specified. (Note 2)
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LT3596E is guaranteed to meet performance specifications
from 0°C to 125°C junction temperature. Specifications over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LT3596I specifications are guaranteed over the full –40°C to 125°C
operating junction temperature range.
Note 3: For maximum operating ambient temperature, see the High
Temperature Considerations section in the Applications Information
section.
Note 4: Guaranteed by design.
LT3596
5
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Typical perForMance characTerisTics
UVLO Threshold EN/UVLO Pin Current VREF Voltage
Switching Frequency SW and DA Current Limit Switch Voltage Drop
VIN Quiescent Current BIAS Quiescent Current VIN, BIAS Shutdown Current
TA = 25°C, unless otherwise noted
VIN VOLTAGE (V)
0
0
VIN CURRENT (mA)
0.4
0.8
1.2
10 20 30 40
3596 G01
50
1.6
2.0
0.2
0.6
1.0
1.4
1.8
60
T = 125°C
T = 25°C
T = –40°C
VBIAS = 5V
BIAS VOLTAGE (V)
0
BIAS CURRENT (mA)
1.0
1.5
2.0
20
3596 G02
0.5
0
–0.5 510 15 25
T = 125°C
T = 25°C
T = –40°C
VIN = 24V
TEMPERATURE (°C)
–50
0.8
1.0
1.4
IVIN
25 75
3596 G03
0.6
0.4
–25 0 50 100 125
0.2
0
1.2
CURRENT (µA)
VIN = 55V
VBIAS = 25V
IVBIAS
TEMPERATURE (°C)
–50
UVLO THRESHOLD (V)
1.7
25
3596 G04
1.4
1.2
–25 0 50
1.1
1.0
1.8
1.6
1.5
1.3
75 100 125
TEMPERATURE (°C)
–50
EN/UVLO CURRENT (µA)
4
5
6
25 75
3596 G05
3
2
–25 0 50 100 125
1
0
VEN/UVLO = 1.4V
TEMPERATURE (°C)
–50
VREF VOLTAGE (V)
2.03
25
3596 G06
2.00
1.98
–25 0 50
1.97
1.96
2.04
2.02
2.01
1.99
75 100 125
VIN = 55V
VIN = 24V
VIN = 6V
TEMPERATURE (°C)
–50
0.8
1.0
1.4
25 75
3596 G07
0.6
0.4
–25 0 50 100 125
0.2
0
1.2
SWITCHING FREQUENCY (MHz)
RT = 33.2k
RT = 220k
TEMPERATURE (°C)
–50
CURRENT LIMIT (mA)
900
1000
1100
ISW
IDA
25 75
3596 G08
800
700
–25 0 50 100 125
600
500
SWITCH CURRENT (mA)
0
0
SWITCH VOLTAGE (mV)
100
300
400
500
1000
700
200 400 500
3596 G09
200
800
900
600
100 300 600 700 800
T = 125°C
T = 25°C
T = –40°C
LT3596
6
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FB and LED Loop Regulation
Voltage LED Current LED Current Matching
LED Current vs PWM Duty Cycle LED Current vs CTRLn Voltage
Adaptive Loop Switching
Waveforms (with PWM Dimming)
Boost Diode Voltage Soft-Start 60V Buck Switching Waveforms
Typical perForMance characTerisTics
TA = 25°C, unless otherwise noted
CURRENT (mA)
0 25
0
BOOST DIODE VOLTAGE (V)
0.4
1.0
50 100 125
3596 G10
0.2
0.8
0.6
75 150 175
EN/UVLO
5V/DIV
SW
50V/DIV
VOUT
20V/DIV
400µs/DIV 3596 G11
IL
500mA/DIV
SW
20V/DIV
VOUT
20V/DIV
400ns/DIV 3596 G12
IL
500mA/DIV
TEMPERATURE (°C)
–50 –25
0.9
REGULATION VOLTAGE (V)
1.1
1.4
VFB
050 75
3596 G13
1.0
1.3
1.2
25 100 125
VLED
TEMPERATURE (°C)
–50
LED CURRENT (mA)
101
102
103
25 75
3596 G14
100
99
–25 0 50 100 125
98
97
LED1
LED2
LED3
RISETn = 20k
TEMPERATURE (°C)
–50
MATCHING (%)
0.75
25
3596 G15
0
–0.50
–25 0 50
–0.75
–1.00
1.00
0.50
0.25
–0.25
75 100 125
CH1
CH2
CH3
RISETn = 20k
PWM DUTY CYCLE (%)
0.001
0.0001
LED CURRENT (mA)
0.001
0.01
0.1
1
10
100
0.01 0.1 1 10
3596 G16
100
RISETn = 20k
CTRLn VOLTAGE (V)
0
0
LED CURRENT (mA)
25
50
75
100
0.25 0.5 0.75 1
3596 G17
1.25 1.5
RISETn = 20k
ILED
100mA/DIV
VOUT
10V/DIV
VLED
10V/DIV
VSW
100V/DIV
200µs/DIV 3596 G18
LT3596
7
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PWM Dimming Waveforms
(Nonoverlapping PWM Signals)
10,000:1 PWM Dimming at 100Hz
PWM Dimming Waveforms
(Overlapping PWM Signals)
Typical perForMance characTerisTics
TA = 25°C, unless otherwise noted
1,000:1 PWM Dimming at 100Hz
ILED1
100mA/DIV
ILED2
100mA/DIV
PWM1
5V/DIV
PWM2
5V/DIV
2ms/DIV 3596 G21
ILED1
100mA/DIV
ILED2
100mA/DIV
PWM1
5V/DIV
PWM2
5V/DIV
2ms/DIV 3596 G22
LED Open-Fault Waveforms
ILED1
100mA/DIV
VSW
50V/DIV
VLED
1V/DIV
VOUT
20V/DIV
20µs/DIV 3596 G23
LED Short to VOUT Waveforms
VLED
20V/DIV
VFAULT
5V/DIV
ILED
100mA/DIV
VOUT
20V/DIV
10ms/DIV 3596 G24
FAULT Output Voltage VTSET for LED Current Derating
IFAULT (mA)
0
0
FAULT VOLTAGE (mV)
200
400
600
800
0.25 0.5 0.75 1
3596 G25
1.25 1.5 1.75 2
T = 125°C
T = 25°C
T = –40°C
TSET LED Current Derating
TEMPERATURE (°C)
–50 –25
0.3
VTSET (V)
0.5
0.8
050 75
3596 G26
0.4
0.7
0.6
25 100 125
TEMPERATURE (°C)
25
ILED (mA)
60
80
100
105
3596 G27
40
20
045 65 85 125
VTSET = 0.68V
LT3596
8
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pin FuncTions
FB (Pin 2): Feedback Pin. This pin is regulated to the
internal bandgap voltage. The maximum buck output
voltage is set by connecting this pin to a resistor divider
from VOUT
.
EN/UVLO (Pin 4): Enable and Undervoltage Lockout Pin.
Accurate 1.5V falling threshold. UVLO threshold is pro-
grammed by using a resistor divider from VIN.
TSET (Pin 6): Thermal Regulation Pin. Programs the
LT3596 junction temperature at which LED current begins
to derate.
VREF (Pin 7): 2V Reference Output Pin. This pin sources
up to 200µA and is used to program TSET and CTRLM.
GND (Pin 9/Exposed Pad Pin 53): Ground Pin. This is
the ground for both the IC and the switching converter.
Exposed pad must be soldered to PCB ground.
NC (Pins 11, 12, 18, 22, 23, 26, 34, 35, 39, 41, 43): No
Connection Pins. Tie to ground if unused.
CTRLM (Pin 13): Master Control Pin. LED current derating
vs temperature is achievable for all channels if the voltage
on CTRLM has a negative coefficient using an external
NTC resistor divider from VREF
.
ISET1, ISET2, ISET3 (Pins 14, 15, 16): LED Current Pro-
gramming Pin. Resistor to ground programs full-scale
LED current.
RT (Pin 17): Switching Frequency Programming Pin. A
resistor to ground programs switching frequency between
200kHz and 1MHz. For the SYNC function, choose the
resistor to program a frequency 20% slower than the
SYNC pulse frequency.
VOUT (Pin 19): Buck Output. This is the buck regulator
output voltage sense into the IC.
LED1, LED2, LED3 (Pins 20, 21, 24): Constant-Current
Sink Pin. These are three LED driver outputs, each contain-
ing an open collector, constant current sink. All outputs are
matched within ±1.5% and are individually programmed
up to 100mA using an external resistor at the ISET1-3 pin.
Outputs are rated to allow a maximum VOUT of 42V. Con-
nect the cathode of the LED string to LED1-3. Connect the
anode of the LED string to VOUT
.
FAULT (25): Fault Detection Pin. Open-collector pin used
to report open LED faults. FAULT must be externally pulled
to a positive supply.
SYNC (Pin 27): External Clock Synchronization Pin. When
an external clock drives this pin, the buck regulator is
synchronized to that frequency. Frequency programmed
by the RT pin resistor must be at least 20% slower than
the SYNC pin clock frequency.
PWM1, PWM2, PWM3 (Pins 30, 29, 28): PWM Dimming
Control Pin. When driven to a logic high, the LED1-3 current
sink is enabled. Channels can be individually disabled by
tying PWM1-3 to ground. If PWM dimming is not desired
then the pin should be connected to VREF
.
CTRL1, CTRL2, CTRL3 (Pins 33, 32, 31): Analog Dimming
Control Pin. This pin is used to dim the LED current in an
analog fashion. If the pin is tied to a voltage lower than
1.0V, it will linearly reduce the LED current. If unused the
pin must be connected to VREF
.
BIAS (37): Supply Pin. This pin is the supply for an internal
voltage regulator for analog and digital circuitry. BIAS must
be locally bypassed with a 4.7µF capacitor.
DA (44): Catch Diode Anode. This pin is used to provide
frequency foldback in extreme situations.
BOOST (Pin 46): Boost Capacitor Pin. This pin is used to
provide a voltage above the input voltage when the switch
is on. It supplies current to the switch driver.
SW (Pin 48): Switch Pin. Connect the inductor, catch diode
and boost capacitor to this pin.
VIN (Pins 50, 51): Input Supply Pins. Pins are electrically
connected inside the package. VIN must be locally bypassed
with a 10µF capacitor to ground.
LT3596
9
3596fa
block DiagraM
LEDn
20, 21, 24
3596 F01
BIAS
START-UP
REFERENCE
SOFT-START
AND
CLAMP
EN/UVLO
4
VIN
50-51
VREF
7
SYNC
27
RT
17
TSET
540mV
PTAT
6
CTRLM
13
CTRLn 33-31
PWMn 30-28
ISETn 14-16
BOOST 46
SW
BIAS 37
OSC S
RQ
SLOPE
COMP
–+
48
DA 44
GND 9
FB 2
VOUT 19
FAULT
25
53
–
+
1.21V
VC
1V
+
–
CHANNELS 1 TO 3
CONVERSION
AND
CONTROL
PWM
DIMMING
LOGIC
EXPOSED PAD
LED
FAULT
PROTECTION
+
–
+
–
LED
DRIVE
CIRCUITRY
LOGIC
Figure 1. Block Diagram
LT3596
10
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operaTion
The LT3596 uses a constant-frequency, peak current mode
control scheme to provide excellent line and load regula-
tion. Operation is best understood by referring to the Block
Diagram (Figure 1). The bias, start-up, reference, oscillator,
TSET amplifier and the buck regulator are shared by the
three LED current sources. The conversion and control,
PWM dimming logic, LED fault detection, and LED drive
circuitry are identical for all three current sources.
Enable and undervoltage lockout (UVLO) are both con-
trolled by a single pin. If the EN/UVLO pin falls below
1.51V (typical), an accurate comparator turns off the LED
drivers and the buck regulator. If the pin continues to fall
to less than 0.4V, the part enters a low quiescent current
shutdown mode.
The LT3596 contains three constant-current sink LED
drivers. These drivers sink up to 100mA with 1.5% match-
ing accuracy between LED strings. The LED strings are
powered from the buck converter.
The buck converter contains an adaptive loop that adjusts
the output voltage based on LED string voltage to ensure
maximum efficiency. External compensation and soft-start
components are not required, minimizing component
count and simplifying board layout. An external resistor
programs the buck’s switching frequency between 200kHz
and 1MHz. The frequency can also be synchronized to an
external clock using the SYNC pin.
Step-Down Adaptive Control
Adaptive control of the output voltage maximizes system
efficiency. This control scheme regulates the output voltage
to the minimum that ensures all three LED strings turn
on. This accounts for the variation in the forward voltage
of the LEDs, and minimizes the power dissipation across
the internal current sources.
Activation of the adaptive loop is set by the status of the
PWMn pins. If any channel’s PWM pin is low, then the buck
regulator output ascends to an externally programmed out-
put voltage. This voltage is always set above the maximum
voltage drop of the LEDs. This guarantees that the buck
output voltage is high enough to immediately supply the
LED current once the strings are reactivated. As soon as
all of the PWM pins transition high, the output voltage of
the buck drops until the adaptive loop regulates the output
with about 1V across the LED current sinks. This scheme
optimizes the efficiency for the system since the output
voltage regulates to the minimum voltage required for all
three LED strings.
LED Current
Each LED string current is individually programmed to
a maximum of 100mA with 1.5% matching accuracy
between the strings. An external resistor on the ISETn
pin programs the maximum current for each string. The
CTRLn pin is used for analog dimming. Digital dimming
is programmed using the PWMn pin. A dimming ratio of
10,000:1 is achievable at a frequency of 100Hz.
Fault Protection and Reporting
The LT3596 features diagnostic circuitry that protects
the system in the event that a LEDn pin is shorted to an
undesirable voltage. The LT3596 detects when the LEDn
voltage exceeds 12V or is within 1.2V of VOUT when the LED
string is sinking current. If either faulted condition occurs,
the channel is disabled until the fault is removed. The fault
is reported on FAULT until the fault has cleared.
The LT3596 also offers open-LED detection and report-
ing. If a LED string is opened and no current flows in the
string, then a fault is reported on FAULT. A fault is also
reported if the internal die temperature reaches the TSET
programmed derating limit. LED faults are only reported
if the respective PWM signal is high.
LT3596
11
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applicaTions inForMaTion
Inductor Selection
Inductor values between 100µH and 470µH are recom-
mended for most applications. It is important to choose
an inductor that can handle the peak current without
saturating. The inductor DCR (copper wire resistance)
must also be low in order to minimize I2R power losses.
Table 1 lists several recommended inductors.
Table 1. Recommended Inductors
PART
L
(µH)
MAX
DCR
(Ω)
CURRENT
RATING
(A) VENDOR
MSS1038
MSS1038
MSS1246T
100
220
470
0.3
0.76
0.935
1.46
0.99
1.0
Coilcraft
www.coilcraft.com
CDRH10D68
CDRH12D58R
100
220
470
0.205
0.362
0.67
1.5
1.0
1.01
Sumida
www.sumida.com
DS1262C2 100
220
0.17
0.35
1.5
1.0
Toko
www.toko.com
VLF10040 100
220
0.22
0.47
1.3
0.9
TDK
www.tdk.com
DR124
DR127
DR74
100
220
470
100
0.26
0.56
0.861
0.383
1.79
1.15
1.6
0.99
Coiltronics
www.cooperet.com
744771220 220 0.40 1.2 Würth Elektronik
www.we-online.com
Capacitor Selection
Low ESR (equivalent series resistance) capacitors should
be used at the outputs to minimize output ripple voltage.
Use only X5R or X7R dielectrics, as these materials retain
their capacitance over wider voltage and temperature
ranges than other dielectrics. Table 2 lists some suggested
manufacturers. Consult the manufacturers for detailed
information on their entire selection of ceramic surface
mount parts.
Table 2. Recommended Ceramic Capacitor Manufacturers
Taiyo Yuden www.t-yuden.com
AVX www.avxcorp.com
Murata www.murata.com
Kemet www.kemet.com
TDK www.tdk.com
Typically 10µF capacitors are sufficient for the VIN and BIAS
pins. The output capacitor for the buck regulator depends
on the number of LEDs and switching frequency. Refer to
Table 3 for the proper output capacitor selection.
Table 3. Recommended Output Capacitor Values
(Volts/LED = 3.5V)
SWITCHING
FREQUENCY (kHz) # LEDs COUT (µF)
1000 1 to 3 6.8
>3 4.7
500 1 to 3 10
>3 6.8
200 1 to 3 22
>3 10
Diode Selection
Schottky diodes, with their low forward voltage drop and
fast switching speed, must be used for all LT3596 ap-
plications. Do not use P-N junction diodes. The diode’s
average current rating must exceed the application’s aver-
age current. The diode’s maximum reverse voltage must
exceed the application’s input voltage. Table 4 lists some
recommended Schottky diodes.
Table 4. Recommended Diodes
PART
MAX
CURRENT
(A)
MAX
REVERSE
VOLTAGE
(V) MANUFACTURER
DFLS160 1 60 Diodes, Inc.
www.diodes.com
CMMSH1-60 1 60 Central Semiconductor
www.centralsemi.com
ESIPB 1 100 Vishay
www.vishay.com
Undervoltage Lockout (UVLO)
EN/UVLO programs the UVLO threshold by connecting the
pin to a resistor divider from VIN as shown in Figure 2.
Select R1 and R2 according to the following equation:
V V R
R
IN UVLO( ) . •= +
1 51 1 2
1
LT3596
12
3596fa
applicaTions inForMaTion
In UVLO an internal 5.1µA (typical) pull-down current
source is connected to the pin for programmable UVLO
hysteresis. The hysteresis is set according to the follow-
ing equation:
VUVLO(HYST) = 5.1µA • R2
Care must be taken if too much hysteresis is programmed,
the pin voltage might drop too far and cause the current
source to saturate.
Once the EN/UVLO pin goes below 0.4V, the part enters
shutdown.
Programming Maximum LED Current
Maximum LED current is programmed by placing a resistor
(RISETn) between the ISETn pin and ground. RISETn values
between 20k and 100k can be chosen to set the maximum
LED current between 100mA and 20mA respectively.
The LED current is programmed according to the follow-
ing equation:
I V R
LED ISET
1-3 =12000
•
n
where RISETn is in kΩ and ILEDn is in mA. See Table 5 and
Figure 3 for resistor values and corresponding programmed
LED current.
Table 5. RISETn Value for LED Current
RISETn VALUE (kΩ) LED CURRENT (mA)
20 100
24.9 80
33.2 60
49.9 40
100 20
RISETn (kΩ)
0
LED CURRENT (mA)
40
60
100
3596 F03
20
025 50 75
100
80
Figure 3. RISETn Value for LED Current
LED Current Dimming
The LT3596 has two different types of dimming control.
The LED current is dimmed using the CTRLn pin or the
PWMn pin.
For some applications, a variable DC voltage that adjusts
the LED current is the preferred method for brightness
control. In this case, the CTRLn pin is modulated to set
the LED dimming. As the CTRLn pin voltage rises from
0V to 1V, the LED current increases from 0mA to the
maximum programmed LED current in a linear fashion
(see Figure 4). As the CTRLn pin increases beyond 1V,
the maximum programmed LED current is maintained.
If this type of dimming control is not desired, the CTRLn
pin can be connected to VREF
.
CTRLn VOLTAGE (V)
0
0
LED CURRENT (mA)
25
50
75
100
0.25 0.5 0.75 1
3596 F04
1.25 1.5
RISETn = 20k
Figure 4. LED Current vs CTRLn Voltage
+
–
1.51V
3596 F02
EN/UVLO
LT3596
R2
VIN
R1
Figure 2. EN/UVLO Control
LT3596
13
3596fa
applicaTions inForMaTion
Table 6. TSET Programmed Junction Temperature
TJ (°C) R1 (kΩ) R2 (kΩ)
85 49.9 97.6
100 49.9 90.9
115 49.9 84.5
The TSET pin must be tied to VREF if the temperature
protection feature is not desired.
LED1-3
CURRENT
MAX ILED
3596 F05
tON(PWM)
tPWM
Figure 5. LED Current Using PWM Dimming
For True Color PWM dimming, the LT3596 provides up
to 10,000:1 PWM dimming range at 100Hz. This is done
by reducing the duty cycle of the PWMn pin from 100%
to 0.01% for a PWM frequency of 100Hz (see Figure 5).
This equates to a minimum on time of 1µs and a maxi-
mum period of 10ms. PWM duty cycle dimming allows
for constant LED color to be maintained over the entire
dimming range.
3596 F06
TSET
VREF
LT3596
R2
R1
Figure 6. Programming the TSET Pin
Using the TSET Pin for Thermal Protection
The LT3596 contains a special programmable thermal
regulation loop that limits the internal junction tempera-
ture. This thermal regulation feature provides important
protection at high ambient temperatures. It allows an
application to be optimized for typical, not worst-case,
ambient temperatures with the assurance that the LT3596
automatically protects itself and the LED strings under
worst-case conditions.
As the ambient temperature increases, so does the internal
junction temperature of the part. Once the programmed
maximum junction temperature is reached, the LT3596
linearly reduces the LED current, as needed, to maintain
this junction temperature. This is only achieved when
the ambient temperature stays below the maximum pro-
grammed junction temperature. If the ambient temperature
continues to rise above the programmed maximum junc-
tion temperature, the LED current will reduce to less than
10% of the full current.
A resistor divider from the VREF pin programs the maximum
IC junction temperature as shown in Figure 6.
Table 6 shows commonly used values for R1 and R2.
Choose the ratio of R1 and R2 for the desired junction
temperature limit as shown in Figure 7.
TEMPERATURE (°C)
–50 –25
0.3
VTSET (V)
0.5
0.8
050 75
3596 F07
0.4
0.7
0.6
25 100 125
Figure 7. VTSET for LED Current Derating
LED Current Derating Using the CTRLM Pin
A useful feature of the LT3596 is its ability to program
a derating curve for maximum LED current versus tem-
perature. LED data sheets provide curves of maximum
allowable LED current versus temperature to warn against
exceeding this current limit and damaging the LED. The
LT3596 allows the output LEDs to be programmed for
maximum allowable current while still protecting the
LEDs from excessive currents at high temperature. This
is achieved by programming a voltage at the CTRLM pin
with a negative temperature coefficient using a resistor
divider with temperature-dependent resistance (Figure 8).
As ambient temperature increases, the CTRLM voltage
falls below the internal 1V voltage reference, causing
LT3596
14
3596fa
applicaTions inForMaTion
LED currents to be controlled by the CTRLM pin voltage.
The LED current-curve breakpoint and slope versus tem-
perature are defined by the choice of resistor ratios and
use of temperature-dependent resistance in the divider
for the CTRLM pin.
Table 7 shows a list of manufacturers/distributors of NTC
resistors. There are several other manufacturers available.
The chosen supplier should be contacted for more detailed
information.
Table 7. NTC Resistor Manufacturers/Distributors
Murata www.murata.com
TDK Corporation www.tdk.com
Digi-Key www.digikey.com
If an NTC resistor is used to indicate LED temperature, it
is effective only if the resistor is placed as close as pos-
sible to the LED strings. LED derating curves shown by
manufacturers are listed for ambient temperature. The
NTC resistor should have the same ambient temperature
as the LEDs. Since the temperature dependence of an
NTC resistor is nonlinear as a function of temperature, it
is important to obtain its temperature characteristics from
the manufacturer. Hand calculations of the CTRLM voltage
are then performed at each given temperature using the
following equation:
V V R
R R
CTRLM REF
=+
•1
1 2
This produces a plot of VCTRLM versus temperature. From
this curve, the LED current is found using Figure 9.
Several iterations of resistor value calculations may be
necessary to achieve the desired breakpoint and slope of
the LED current derating curve.
If calculating the CTRLM voltage at various temperatures
gives a downward slope that is too strong, use alternative
resistor networks (B, C, D in Figure 8). They use tempera-
ture independent resistance to reduce the effects of the
NTC resistor over temperature.
Murata Electronics provides a selection of NTC resistors
with complete data over a wide range of temperatures.
In addition, a software tool is available which allows the
user to select from different resistor networks and NTC
resistor values, and then simulate the exact output volt-
age curve (CTRLM behavior) over temperature. Referred
to as the Murata Chip NTC Thermistor Output Voltage
Simulator, users can log on to www.murata.com and
download the software followed by instructions for creat-
ing an output voltage VOUT (CTRLM) from a specified VCC
supply (VREF).
The CTRLM pin must be tied to VREF if the temperature
derating function is not desired.
Programming Switching Frequency
The switching frequency of the LT3596 can be programmed
between 200kHz and 1MHz by an external resistor con-
nected between the RT pin and ground. Do not leave this
pin open. See Table 8 and Figure 10 for resistor values
and corresponding frequencies.
Selecting the optimum switching frequency depends on
several factors. Inductor size is reduced with higher fre-
quency, but efficiency drops slightly due to higher switching
Figure 9. LED Current vs CTRLM Voltage
Figure 8. Programming the CTRLM Pin
3596 F08
CTRLM
VREF
LT3596
R2 RNTC RNTC
RNTC
(8a)
R1
(OPTION A TO D)
RX
(8b)
RX
RX
(8c)
RX
(8d)
CTRLM VOLTAGE (V)
0
0
LED CURRENT (mA)
25
50
75
100
0.25 0.5 0.75 1
3596 F04
1.25 1.5
RISETn = 20k
LT3596
15
3596fa
applicaTions inForMaTion
losses. Some applications require very low duty cycles to
drive a small number of LEDs from a high supply. Low
switching frequency allows a greater range of operational
duty cycle and so a lower number of LEDs can be driven.
In each case, the switching frequency can be tailored to
provide the optimum solution. When programming the
switching frequency, the total power losses within the IC
should be considered.
Table 8. RT Resistor Selection
RT VALUE (kΩ) SWITCHING FREQUENCY (MHz)
33.2 1.0
80.6 0.5
220 0.2
The SYNC pin must be grounded if the clock synchroniza-
tion feature is not used. When the SYNC pin is grounded,
the internal oscillator controls the switching frequency of
the converter.
Operating Frequency Trade-Offs
Selection of the operating frequency is a trade-off between
efficiency, component size, input voltage and maximum
output voltage. The advantage of high frequency operation
is smaller component size and value. The disadvantages
are lower efficiency and lower maximum output voltage
for a fixed input voltage. The highest acceptable switch-
ing frequency (fSW(MAX)) for a given application can be
calculated as follows:
fV V
t V V V
SW MAX D OUT
ON MIN D IN SW
( ) ( ) –
=+
+
( )
where VIN is the typical input voltage, VOUT is the output
voltage, VD is the catch diode drop (~0.5V) and VSW is the
internal switch drop (~0.4V at max load). This equation
shows that slower switching is necessary to accommodate
high VIN/VOUT ratios. The input voltage range depends on
the switching frequency due to the finite minimum switch
on and off times. The switch minimum on and off times
are 150ns.
Adaptive Loop Control
The LT3596 uses an adaptive control mechanism to set
the buck output voltage. This control scheme ensures
maximum efficiency while not compromising minimum
PWM pulse widths. When any PWMn is low, the output
of the buck rises to a maximum value set by an external
resistor divider to the FB pin. When all PWMn pins go
high, the output voltage is adaptively reduced until the
voltage across the LED current sink is about 1V. Figure
11 shows how the maximum output voltage is set by an
external resistor divider.
Figure 10. Programming Switching Frequency
Figure 11. Programming Maximum VOUT
RT (kΩ)
0
0
SWITCHING FREQUENCY (MHz)
0.2
0.4
0.6
0.8
1.0
1.2
55 110 165 220
3596 F10
3596 F11
FB
VOUT
VOUT
LT3596
R2
R1
Switching Frequency Synchronization
The nominal operating frequency of the LT3596 is pro-
grammed using a resistor from the RT pin to ground. The
frequency range is 200kHz to 1MHz. In addition, the internal
oscillator can be synchronized to an external clock applied
to the SYNC pin. The synchronizing clock signal input to
the LT3596 must have a frequency between 240kHz and
1MHz, a duty cycle between 20% and 80%, a low state
below 0.4V and a high state above 1.6V. Synchronization
signals outside of these parameters cause erratic switching
behavior. For proper operation, an RT resistor is chosen
to program a switching frequency 20% slower than the
SYNC pulse frequency. Synchronization occurs at a fixed
delay after the rising edge of SYNC.
LT3596
16
3596fa
applicaTions inForMaTion
The maximum output voltage must be set to exceed the
maximum LED drop plus 1.07V by a margin greater than
15%. However, this margin must not exceed a value of
10V. This ensures proper adaptive loop control. The equa-
tion below is used to estimate the resistor divider ratio.
The sum of the resistors should be approximately 100k
to avoid noise coupling to the FB pin.
V V V V R
R
OUT MAX LED MAX( ) ( )
. • . . •= +
( )
= +
1 15 1 07 1 21 1 2
1
VOUT(MAX) = VLED(MAX) + 1.07V + VMARGIN
VMARGIN ≤ 10V
Minimum Input Voltage
The minimum input voltage required to generate an output
voltage is limited by the maximum duty cycle and the
output voltage (VOUT) set by the FB resistor divider. The
duty cycle is:
DC V V
V V V
D OUT
IN CESAT D
=+
+–
where VD is the Schottky forward drop and VCESAT is the
saturation voltage of the internal switch. The minimum
input voltage is:
VV V
DC V V
IN MIN
D OUT MAX
MAX CESAT D( )
( ) –=+
+
where VOUT(MAX) is calculated from the equation in the
Adaptive Loop Control section, and DCMAX is the minimum
rating of the maximum duty cycle.
Start-Up
At start-up, when VOUT reaches 90% of the FB programmed
output voltage, the adaptive loop is enabled. At this point,
the LED string with the highest voltage drop is selected. The
output voltage reduces until the selected string’s LED pin
is about 1V. This regulation method ensures that all three
LED strings run their programmed current at a minimum
output voltage despite mismatches in LED forward volt-
age. This minimizes the drop across the internal current
sources and maximizes system efficiency.
Another benefit of this regulation method is that the LT3596
starts up with 10,000:1 dimming even if the PWMn pulse
width is 1µs. Since VOUT starts up even if PWMn is low,
the part achieves high dimming ratios with narrow pulse
widths within a couple of PWMn clock cycles.
High Temperature Considerations
The LT3596 provides three channels for LED strings with
internal NPN devices serving as constant current sources.
When LED strings are regulated, the lowest LED pin voltage
is typically 1V. For 100mA of LED current with a 100%
PWM dimming ratio, at least 300mW is dissipated within
the IC due to current sources. If the forward voltages
of the three LED strings are very dissimilar, significant
power dissipation will occur. Thermal calculations must
include the power dissipation in the current sources in
addition to conventional switch DC loss, switch transient
loss and input quiescent loss. For best efficiency, it is
recommended that each LED string have approximately
the same voltage drop.
In addition, the die temperature of the LT3596 must be
lower than the maximum rating of 125°C. This is generally
not a concern unless the ambient temperature is above
100°C. Care should be taken in the board layout to ensure
good heat sinking of the LT3596. The maximum load cur-
rent (300mA) must be derated as the ambient temperature
approaches 125°C. The die temperature is calculated by
multiplying the LT3596 power dissipation by the thermal
resistance from junction to ambient. Power dissipation
within the LT3596 is estimated by calculating the total
power loss from an efficiency measurement and subtract-
ing the losses of the catch diode and the inductor. Thermal
resistance depends on the layout of the circuit board, but
32°C/W is typical for the 5mm × 8mm QFN package.
Board Layout
As with all switching regulators, careful attention must
be paid to the PCB layout and component placement. To
prevent electromagnetic interference (EMI) problems,
proper layout of high frequency switching paths is essential.
Minimize the length and area of all traces connected to the
switching node (SW). Always use a ground plane under
the switching regulator to minimize interplane coupling.
Resistors connected between ground and the CTRL1-3,
CTRLM, FB, TSET, ISETn  
, RT and EN/UVLO pins are best
connected to a quiet ground.
LT3596
17
3596fa
Typical applicaTions
24V 200kHz Step-Down 4W, 100mA LED Driver
VIN
EN/UVLO
LT3596
SYNC
SYNC
PWM1
PWM2
PWM3
PWM1
PWM2
PWM3
CTRL1
CTRL2
CTRL3
CTRL1
CTRL2
CTRL3
RT
FAULTFAULT
BIAS
270k
10µF
VIN
24V
91k
220k
VREF
TSET
CTRLM
10k
90.9k
49.9k 20k 20k 20k
3696 TA02a
100k
MURATA NCP18WF104
100k
BIAS
BOOST
SW
DA
GND
FB
LED1
LED2
LED3
ISET1
ISET2
ISET3
VOUT
VOUT
10µF
VOUT
100nF
100k
7.32k
470µH
z13.5V PER
LED STRING
Efficiency
LED CURRENT (mA)
0
EFFICIENCY (%)
60
80
100
80
3596 TA02b
40
20
020 40 60 100
LT3596
18
3596fa
12V 1MHz Step-Down 100mA Single Pixel R-G-B Driver
VIN
EN/UVLO
LT3596
SYNCSYNC
PWM1
PWM2
PWM3
PWM1
PWM2
PWM3
CTRL1
CTRL2
CTRL3
CTRL1
CTRL2
CTRL3
RT
FAULTFAULT
BIAS
270k
10µF
VIN
12V
91k
33.2k
VREF
TSET
CTRLM
10k
90.9k
49.9k 20k 20k 20k
3696 TA03a
100k
MURATA NCP18WF104
100k
BIAS
BOOST
SW
DA
GND
FB
LED1
LED2
LED3
ISET1
ISET2
ISET3
VOUT
VOUT
6.8µF
VOUT
100nF
100k
14.7k
100µH
z8V PER
LED STRING
Efficiency
LED CURRENT (mA)
0
EFFICIENCY (%)
60
80
100
80
3596 TA03b
40
20
020 40 60 100
Typical applicaTions
LT3596
19
3596fa
Typical applicaTions
Efficiency
48V 500kHz Step-Down 10W, 100mA LED Driver
VIN
EN/UVLO
LT3596
SYNCSYNC
PWM1
PWM2
PWM3
PWM1
PWM2
PWM3
CTRL1
CTRL2
CTRL3
CTRL1
CTRL2
CTRL3
RT
FAULTFAULT
BIAS
270k
10µF
VIN
48V
91k
80.6k
VREF
TSET
CTRLM
10k
90.9k
49.9k 20k 20k 20k
3696 TA04a
100k
MURATA NCP18WF104
100k
BIAS
BOOST
SW
DA
GND
FB
LED1
LED2
LED3
ISET1
ISET2
ISET3
VOUT
4.7µF
5V
BIAS
6.8µF
VOUT
z36V PER
LED STRING
100nF
100k
3.01k
220µH
LED CURRENT (mA)
0
EFFICIENCY (%)
60
80
100
80
3596 TA04b
40
20
020 40 60 100
10,000:1 PWM Dimming at 100Hz
LT3596
20
3596fa
package DescripTion
UHG Package
Variation: UHG52 (39)
52-Lead Plastic QFN (5mm × 8mm)
(Reference LTC DWG # 05-08-1846 Rev B)
5.00 p 0.10
NOTE:
1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
PIN 1
TOP MARK
(SEE NOTE 6)
5150484644
43
41
39
37
35
34
33
32
31
30
29
28
27
43
48 46 4451 50
41
39
37
35
34
33
32
31
30
29
28
27
2
4
6
7
9
11
12
13
14
15
16
17
2
4
6
7
9
11
12
13
14
15
16
17
181920212223242526
BOTTOM VIEW—EXPOSED PAD
5.90 p0.10
6.40 REF
8.00 p 0.10
0.75 p 0.05
0.75 p 0.05
R = 0.10
TYP
R = 0.10
TYP
0.20 p 0.05
(UHG39) QFN 0410 REV B
0.40 BSC
0.80 BSC
0.70 TYP
0.60 TYP
0.200 REF
0.00 – 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
3.20 REF
0.40 p0.10
0.00 – 0.05
18 19 20 21 22 23 24 25 26
0.70 p 0.05
41 39 37 35 34 33 32 31 30 29 28 27
26
25
24
23
22
21
20
19
18
1716151413121197642
43
44
46
48
50
51
0.40 BSC0.80 BSC
6.40 REF
3.20 REF
4.10 p 0.05
5.50 p 0.05
0.20 p 0.05
5.90 p0.05
2.90 p0.05
7.10 p 0.05
8.50 p 0.05
PACKAGE
OUTLINE
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.20mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
PIN 1 NOTCH
R = 0.30 TYP OR
0.35 s 45o CHAMFER
2.90 p0.10
LT3596
21
3596fa
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
revision hisTory
REV DATE DESCRIPTION PAGE NUMBER
A 9/10 Added “
≈
28V per LED String” to Typical Application drawing 1, 22
Added text and equations to Adaptive Loop Control section in Applications Information 16
Added “
≈
13.5V per LED String” and “
≈
8V per LED String” to Typpplications drawings 17
LT3596
22
3596fa
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
LINEAR TECHNOLOGY CORPORATION 2010
LT 0910 • PRINTED IN USA
relaTeD parTs
Typical applicaTion
48V 1MHz Step-Down 8W, 100mA LED Driver (Eight White LEDs per Channel)
10,000:1 PWM Dimming at 100Hz
PART NUMBER DESCRIPTION COMMENTS
LT3476 Quad Output 1.5A, 2MHz High Current LED Driver with
1000:1 Dimming
VIN: 2.8V to 16V, VOUT(MAX) = 36V, True Color PWM Dimming = 1000:1,
ISD < 10µA, 5mm × 7mm QFN-10 Package
LT3496 45V, 2.1MHz 3-Channel (ILED = 1A) Full-Featured LED
Driver
VIN: 3V to 30V (40VMAX), VOUT(MAX ) = 45V, True Color PWM
Dimming = 3000:1, ISD < 1µA, 4mm × 3mm QFN-28 Package
LT3590 48V, 850kHz 50mA Buck Mode LED Driver VIN: 4.5V to 55V, True Color PWM Dimming = 200:1, ISD < 15µA,
2mm × 2mm DFN-6 and SC70 Packages
LT3595 45V, 2MHz 16-Channel Full-Featured LED Driver VIN: 4.5V to 55V, VOUT(MAX) = 45V True Color PWM Dimming = 5000:1,
ISD < 1µA, 5mm × 9mm QFN-56 Package
LT3598 44V, 1.5A, 2.5MHz Boost 6-Channel LED Driver VIN: 3V to 30V (40VMAX), VOUT(MAX) = 44V, True Color PWM
Dimming = 1000:1, ISD < 1µA, 4mm × 4mm QFN-24 Package
LT3599 2A Boost Converter with Internal 4-String 150mA LED
Ballaster
VIN: 3V to 30V, VOUT(MAX) = 44V, True Color PWM Dimming = 1000:1,
ISD < 1µA, 5mm × 5mm QFN-32 and TSSOP-28 Packages
LT3754 16-Channel × 50mA LED Driver with 60V Boost Controller
and PWM Dimming
VIN: 6V to 40V, VOUT(MAX) = 45V, True Color PWM Dimming = 3000:1,
ISD < 1µA, 5mm × 5mm QFN-32 Package
VIN
EN/UVLO
LT3596
SYNCSYNC
PWM1
PWM2
PWM3
PWM1
PWM2
PWM3
CTRL1
CTRL2
CTRL3
CTRL1
CTRL2
CTRL3
RT
FAULTFAULT
BIAS
270k
10µF
VIN
48V
91k
33.2k
VREF
TSET
CTRLM
10k
90.9k
49.9k 20k 20k 20k
3696 TA01a
100k
100k
BIAS
BOOST
SW
DA
GND
FB
LED1
LED2
LED3
ISET1
ISET2
ISET3
VOUT
4.7µF
5V
BIAS
z28V
PER LED
STRING
4.7µF
VOUT
100nF
100k
3.65k
100µH
PWM
2V/DIV
ILED
50mA/DIV
200ns/DIV 3596 TA01b