LINER LT3754 60v triple step-down led driver programmable temperature protection Datasheet

LT3597
60V Triple Step-Down
LED Driver
DESCRIPTION
FEATURES
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Three 100mA Buck Regulators, Each Drives Up to
10 LEDs with Fast NPN Current Sources
Fast Current Sources for <1µs Pulse Widths
(10,000:1 True Color PWM™ Dimming at 100Hz)
LEDs Disconnected in Shutdown
Adaptive VOUT for Increased Efficiency
6V to 60V Input Voltage Range
±2% LED Current Matching
External Resistor Sets LED Current for Each Channel
Internal Compensation and Soft-Start
Programmable Switching Frequency (200kHz to 1MHz)
Synchronizable to External Clock
Open LED Detection and Reporting
Shorted LED Pin Protection and Reporting
Programmable LED Thermal Derating
Programmable Temperature Protection
5mm × 8mm Thermally Enhanced QFN Package
with a 0.6mm High Voltage Pin Spacing
The LT®3597 is a 60V triple step-down LED driver capable
of achieving 10,000:1 digital PWM dimming at 100Hz with
fast NPN current sources driving up to 10 LEDs in each
channel. LED dimming can also be achieved via analog
control of the CTRL1-3 pin.
The step-down switching frequency is programmed between 200kHz and 1MHz. The frequency is also synchronizable to an external clock. The LT3597 provides maximum
LED brightness while adhering to manufacturers’ specifications for thermal derating. The derate temperature is
programmed by placing a negative temperature coefficient
(NTC) resistor on the master control pin.
The LT3597 adaptively controls VOUT in order to achieve
optimal efficiency. Other features include: 2% LED current matching between channels, open LED reporting,
shorted LED protection, programmable LED current, and
programmable temperature protection.
APPLICATIONS
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L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. True Color
PWM is a trademark of Linear Technology Corporation. All other trademarks are the property of
their respective owners.
LED Billboards and Signboards
Mono, Multi, Full-Color LED Displays
Large Screen Display LED Backlighting
Automotive, Industrial, and Medical Displays
TYPICAL APPLICATION
Triple Step-Down RGB Single Pixel LED Driver, 100mA Current
VIN
48V
10µF
VIN
270k
BOOST2
0.1µF 100µH
EN/UVLO
SW2
BOOST1
DA2
SW1
FB2
DA1
VOUT2
LED2
BOOST3
91k
VOUT1
97k
R
3.3µF
100µH
0.1µF
97k
9.1k
G
3.3µF
9.1k
VCC
5V
10,000:1 PWM Dimming at 100Hz
VOUT2
FB1
LT3597
0.1µF 100µH
VOUT1
LED1
BIAS
10µF
3.3µF
33.2k
(1MHz)
ILED
50mA/DIV
97k
DA3
9.1k
FB3
FAULT
PWM1-3
CTRL1-3
SYNC
RT
3
VOUT3
SW3
100k
3
PWM
2V/DIV
ISET1
VOUT3
LED3
VREF
ISET2
ISET3
GND
20k
20k
200ns/DIV
10k
TSET
CTRLM
3597 TA01a
20k
B
82.5k
3597 TA01b
VREF
49.9k
100k
3597f
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LT3597
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
VIN
BST2
SW2
DA2
TOP VIEW
51 50
48
46
44
VIN
Input Voltage (VIN), EN/UVLO....................................60V
BOOST1-3..................................................................85V
BOOST Pin Above SW Pin......................................... 25V
LED1-3, VOUT1-3.........................................................42V
BIAS, FAULT...............................................................25V
VREF, RT, ISET1-3 , TSET, CTRLM....................................3V
FB1-3, CTRL1-3, PWM1-3, SYNC................................6V
Operating Junction Temperature Range
(Notes 2, 3).........................................–40°C to 125°C
Maximum Junction Temperature........................... 125°C
Storage Temperature Range....................–65°C to 150°C
43 DA3
BST1 2
41 SW3
SW1 4
39 BST3
DA1 6
37 BIAS
FB1 7
53
GND
EN/UVLO 9
35 FB3
34 FB2
TSET 11
33 CTRL1
VREF 12
32 CTRL2
CTRLM 13
31 CTRL3
ISET1 14
30 PWM1
ISET2 15
29 PWM2
ISET3 16
28 PWM3
RT 17
27 SYNC
NC
LED3
FAULT
VOUT3
VOUT2
LED2
LED1
GND
VOUT1
18 19 20 21 22 23 24 25 26
UHG PACKAGE
VARIATION: UHG52(39)
52-LEAD (5mm × 8mm) PLASTIC QFN
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
LT3597EUHG#PBF
LT3597EUHG#TRPBF
3597
52-Lead (5mm × 8mm) Plastic QFN
–40°C to 125°C
LT3597IUHG#PBF
LT3597IUHG#TRPBF
3597
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/
3597f
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LT3597
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 = 29V, BIAS = 5V, EN/UVLO = 5V, PWM1-3 = 3.3V,
CTRL1-3 = CTRLM = TSET = 2.0V, VOUT1-3 = 24V, SYNC = 0V, unless otherwise specified. (Note 2)
PARAMETER
CONDITIONS
VIN Operating Voltage
Quiescent Current from VIN
MIN
l
EN/UVLO = 0.4V
BIAS = 5V, Not Switching
BIAS = 0V, Not Switching
Minimum BIAS Voltage
Quiescent Current from BIAS
TYP
6
EN/UVLO = 0.4V
BIAS = 5V, Not Switching
BIAS = 0V, Not Switching, Current Out of Pin
MAX
UNITS
55
V
2.1
4
2
4
6
µA
mA
mA
3
3.1
V
2
60
2
3
150
µA
mA
µA
EN Threshold (Falling)
0.4
0.7
UVLO Threshold (Falling)
1.47
1.51
1.53
V
4
10
5.1
6
nA
µA
1.15
1.22
1.25
V
200
nA
90
78
95
85
EN/UVLO Pin Current (Hysteresis)
EN/UVLO = 1.6V
EN/UVLO = 1.4V
FB1-3 Regulation Voltage
FB1-3 Pin Bias Current
FB = 6V
Maximum Duty Cycle
RT = 220k (200kHz)
RT = 33.2k (1MHz)
Switch Saturation Voltage
ISW1-3 = 100mA
V
%
%
265
mV
Switch Current Limit
400
510
700
mA
DA Pin Current to Stop OSC
225
280
350
mA
700
nA
Switch Leakage
VSW1-3 = 0V
BST1-3 Pin Current
ISW1-3 = 100mA
Switching Frequency
RT = 220k
RT = 33.2k
2
170
900
200
1000
SYNC Input Low
230
1100
0.4
SYNC Input High
1.6
SYNC Frequency Range
RT = 220k
RT = 47k
SYNC Pin Bias Current
VSYNC = 3.3V
Soft-Start Time
(Note 4)
VREF Voltage
IVREF = 0µA
1.96
kHz
kHz
200
nA
2.0
ms
2.04
200
RISET1-3 = 20k, VCTRL = VCTRLM = TSET = 1.5V
TSET Voltage for LED Current Derating
TSET Pin Leakage Current
VTSET = 1.0V
ILED1-3 LED Current
RISET1-3 = 20k
l
98
97
V
1000
2.5
l
kHz
kHz
V
240
Maximum VREF Current
ISET1-3 Pin Voltage
mA
V
µA
1.0
V
540
mV
100
100
200
nA
102
103
mA
mA
3597f
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LT3597
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 = 29V, BIAS = 5V, EN/UVLO = 5V, PWM1-3 = 3.3V,
CTRL1-3 = CTRLM = TSET = 2.0V, VOUT1-3 = 24V, SYNC = 0V, unless otherwise specified. (Note 2)
PARAMETER
CONDITIONS
LED String Current Matching
RISET1-3 = 20k
MIN
l
LED Pin Voltage
Adaptive VOUT Loop Enabled
LED1-3 Open Detection Threshold
LED1-3 Short Protection Threshold (from GND)
PWM1-3 = 3.3V
10
LED1-3 Short Protection Threshold (from VOUT1-3)
VOUT1-3 = 6V
1
LED1-3 Pin Leakage Current
VLED1-3 = 42V
TYP
MAX
UNITS
±0.35
±0.35
±1.5
±2
%
%
1.1
V
0.28
V
1.25
PWM1-3 Input Low Voltage
PWM1-3 Input High Voltage
V
2
V
100
nA
0.4
V
1.6
V
PWM1-3 Pin Bias Current
200
CTRL1-3 Voltage for Full LED Current
CTRL1-3 Pin Bias Current
15
1.2
V
CTRL1-3 = 6V
CTRLM Voltage for Full LED Current
200
nA
200
nA
1.2
CTRLM Pin Bias Current
CTRLM = 3V
FAULT Output Voltage Low
IFAULT = 200µA
FAULT Pin Input leakage Current
FAULT = 25V
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 LT3597E 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
LT3597I specifications are guaranteed over the full –40°C to 125°C
operating junction temperature range.
nA
V
0.11
V
200
nA
Note 3: For Maximum Operating Ambient Temperature, see Thermal
Considerations in the Applications Information section.
Note 4: Guaranteed by design.
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LT3597
TYPICAL PERFORMANCE CHARACTERISTICS
VIN Quiescent Current
VBIAS = 5V
2.5
125°C
2.0
–40°C
25°C
1.5
1.0
VIN = 24V
VIN = 55V
1.75 VBIAS = 25V
125°C
25°C
2.0
1.50
–40°C
1.5
1.0
0.5
0.5
0
Shutdown Current
2.00
2.5
VBIAS CURRENT (mA)
VIN CURRENT (mA)
VBIAS Quiescent Current
3.0
CURRENT (µA)
3.0
TA = 25°C, unless otherwise noted.
10
20
30
40
VIN VOLTAGE (V)
50
–0.5
60
IVIN
IBIAS
5
0
10
15
VBIAS VOLTAGE (V)
20
0
–50
25
–25
0
25
50
75
TEMPERATURE (°C)
100
3597 G02
UVLO Threshold Voltage (Falling)
EN/UVLO Pin Bias Current
1.7
VREF Voltage
2.04
5
125
3597 G03
6
1.8
VREF LOAD = 0µA
2.03
EN/UVLO = 1.4V
1.6
2.02
1.4
1.3
4
VREF VOLTAGE (V)
1.5
CURRENT (µA)
UVLO VOLTAGE (V)
0.75
0.25
3597 G01
3
2
1.2
VIN = 55V
VIN = 24V
2.01
2.00
VIN = 6V
1.99
1.98
1
1.1
–25
0
25
50
75
TEMPERATURE (°C)
100
0
–50
125
–25
75
0
25
50
TEMPERATURE (°C)
3597 G04
100
1.96
–50
125
Switching Frequency
Current Limit
RT = 33.2k
CURRENT (mA)
0.6
0.4
RT = 220k
0.2
–25
0
25
50
75
TEMPERATURE (°C)
SWITCH
400
DA
300
200
100
100
125
3597 G07
100
0
–50
–25
0
25
50
75
TEMPERATURE (°C)
125
Switch Voltage Drop
600
500
0.8
0
25
50
75
TEMPERATURE (°C)
3597 G06
600
1.0
–25
3597 G05
1.2
0
–50
1.97
EN/UVLO = 1.6V
SWITCH VOLTAGE DROP (mV)
1.0
–50
FREQUENCY (MHz)
1.00
0.50
0
0
1.25
100
125
3597 G08
VBIAS = 5V
125°C
500
25°C
400
–40°C
300
200
100
0
0
50
100
150
200
SWITCH CURRENT (mA)
250
3597 G09
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LT3597
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, unless otherwise noted.
Soft-Start
Boost Diode VF
60V Switching Waveforms
800
600
DIODE VF (mV)
VEN/UVLO
5V/DIV
–40°C
700
25°C
500
VSW
20V/DIV
VSW
20V/DIV
125°C
400
200
VOUT
20V/DIV
VOUT
20V/DIV
100
0
IL
100mA/DIV
IL
100mA/DIV
300
2
0
4
6
8
DIODE CURRENT (mA)
3597 G11
400µs/DIV
10
3597 G12
400ns/DIV
3597 G10
Loop Regulation Voltage
LED Current
0.50
LED CURRENT (mA)
VFB
1.2
1.1
VLED
(ADAPTIVE LOOP)
1.0
101
CH1
100
CH2
CH3
99
98
0.9
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
97
–50
125
–25
75
0
25
50
TEMPERATURE (°C)
LED Current vs PWM Duty Cycle
125
10
100
LED CURRENT (mA)
120
1
0.1
0.01
0.001
0.1
1
DUTY CYCLE (%)
10
0
100
3597 G16
CH1
CH2
–0.25
–0.50
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
125
3597 G15
Adaptive Loop Operation
ILED
100mA/DIV
80
VOUT
10V/DIV
60
VLED
10V/DIV
40
VSW
20V/DIV
20
0.01
CH3
LED Current vs CTRL
100
0.0001
0.001
100
0.25
3597 G14
3597 G13
LED CURRENT (mA)
LED CURRENT MATCHING (%)
102
1.3
VOLTAGE (V)
LED Current Matching
103
1.4
0
0
0.25
0.5
0.75
1
CTRL VOLTAGE (V)
1.25
1.5
400µs/DIV
3597 G18
3597 G17
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LT3597
TYPICAL PERFORMANCE CHARACTERISTICS
20,000:1 PWM Dimming (100Hz)
TA = 25°C, unless otherwise noted.
1,000:1 PWM Dimming (100Hz)
PWM
2V/DIV
PWM
2V/DIV
ILED
50mA/DIV
ILED
50mA/DIV
3597 G19
100ns/DIV
Open LED Fault
Shorted LEDs Fault
VOUT
5V/DIV
VOUT
5V/DIV
VLED
2V/DIV
VLED
5V/DIV
ILED
100mA/DIV
ILED
100mA/DIV
VFAULT
5V/DIV
VFAULT
5V/DIV
3597 G21
20ms/DIV
400
TSET LED Current Derating
0.8
120
25°C
200
40°C
150
100
LED CURRENT (mA)
250
0.6
0.5
0.4
0
0.6
0.2
0.4
0.8
FAULT PIN CURRENT (mA)
1
3597 G23
0.3
–50
80
60
40
20
50
0
VTSET = 0.675V
100
0.7
TSET VOLTAGE (V)
FAULT PIN VOLTAGE (mV)
350
125°C
3597 G22
10ms/DIV
TSET Voltage for Temperature
Derating
FAULT Pin Voltage Low
300
3597 G20
2µs/DIV
–25
75
0
25
50
TEMPERATURE (°C)
100
125
3597 G24
0
25
45
65
85
105
TEMPERATURE (°C)
125
3597 G25
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LT3597
PIN FUNCTIONS
BOOST1, BOOST2, BOOST3 (Pins 2, 48, 39): Boost
Capacitor Pin. This pin is used to provide a voltage that
is higher than the input voltage when the switch is on to
supply current to the switch driver.
SW1, SW2, SW3 (Pins 4, 46, 41): Switch Pin. Connect
the inductor, catch diode and boost capacitor to this pin.
DA1, DA2, DA3 (Pins 6, 44, 43): Catch Diode Anode.
This pin is used to provide frequency foldback in extreme
situations.
FB1, FB2, FB3 (Pins 7, 34, 35): Feedback Pin. This pin is
regulated to the internal bandgap voltage. The maximum
Buck output voltage can be set by connecting this pin to
a resistor divider from VOUT1-3.
EN/UVLO (Pin 9): Enable and Undervoltage Lockout Pin.
Accurate 1.51V threshold. UVLO threshold can be programmed by using a resistor divider from VIN. If function
is not required, pin can be tied to the VIN pin.
TSET (Pin 11): Thermal Regulation Pin. Programs the
LT3597 junction temperature at which LED current begins
to derate.
VREF (Pin 12): 2.0V Reference Output Pin. This pin can
sources up to 200µA and can be used to program TSET
and CTRLM.
CTRLM (Pin 13): Master Control Pin. LED current derating
vs temperature is achievable for all channels if the voltage
on CTRLM has a negative temperature coefficient using an
external NTC resistor in a voltage divider from VREF.
ISET1, ISET2, ISET3 (Pins 14, 15, 16): LED Current Programming Pin. A resistor to ground programs full-scale
LED current.
RT (Pin 17): Switching Frequency Programming Pin. A
resistor to ground programs the switching frequency
between 200kHz and 1MHz.
GND (Pin 18, Exposed Pad Pin 53): Ground Pin. This is
the ground for both the IC and the switching converters.
Exposed pad must be soldered to PCB ground.
VOUT1, VOUT2, VOUT3 (Pins 19, 22, 23): 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 3 LED driver outputs, each containing
an open collector, constant current sink. All outputs are
matched within ±2% and are individually programmed up
to 100mA using an external resistor at the ISET1-3 pin.
Outputs are rated to allow a maximum VOUT1-3 of 42V.
Connect the cathode of the LED string to LED1-3. Connect
the anode of the LED string to VOUT1-3.
FAULT (Pin 25): Fault Detection Pin. Open collector pin
used to report open LED faults. FAULT must be externally
pulled to a positive supply through a resistor.
NC (Pin 26): No Connection Pin. Tie to ground.
SYNC (Pin 27): External Clock Synchronization Pin. When
an external clock drives this pin, the Buck regulators are
synchronized to that frequency. Frequency programmed
by the RT pin resistor must be at least 20% less 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. If PWM dimming is not desired, connect
the pin to VREF. Channels can be individually disabled by
tying PWM1-3 to ground.
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 feature is
unused, connect the pin to VREF.
BIAS (Pin 37): Supply Pin. This pin is the supply for an
internal voltage regulator to internal analog and digital
circuitry. BIAS must be locally bypassed with a 2.2µF
capacitor.
VIN (Pins 50, 51): Input Supply Pin. VIN must be locally
bypassed with a 10µF capacitor to ground. Pins 50 and
51 are internally fused.
3597f
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LT3597
BLOCK DIAGRAM
LT3597
VIN
EN/UVLO
BIAS
START-UP
REFERENCE
VREF
BIAS
+ –
BSTn
SYNC
S
OSC
RT
Q
R
SWn
SLOPE
COMP
+
CHANNEL n
n = 1-3
SOFT-START
AND CLAMP
VC
540mV
PTAT
TSET
CTRLM
CTRLn
–
+
CONVERSION
AND
CONTROL
–
+
–
1.22V
+
–
1.1V
GND
FBn
VOUTn
FAULT
LED
FAULT DETECTION
LOGIC
LEDn
ISETn
PWMn
DAn
PWM
DIMMING
LOGIC
LED
DRIVE
CIRCUITRY
GND, EXPOSED PAD
3597 BD
Figure 1. Block Diagram
3597f
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LT3597
OPERATION
The LT3597 uses a constant frequency, internally compensated peak current mode control scheme. Operation
is best understood by referring to the Block Diagram in
Figure 1.
Enable and undervoltage lockout (UVLO) are both controlled by a single pin. If the pin falls below 1.51V, an
accurate comparator turns off the LED drivers and buck
regulators. If the pin continues to fall to less than 0.4V,
the part enters shutdown and consumes less than 2µA.
The LT3597 contains three constant current sink LED
drivers. Each of the three LED strings is powered from
a dedicated adaptive buck converter in order to achieve
maximum efficiency. The frequency of the buck regulators
is programmed from 200kHz to 1MHz using an external
resistor. The frequency can also be synchronized to an
external clock using the SYNC pin.
Internal buck compensation and soft-start requires few
external components and permits simple board layout. A
high-side switch current limit protects the internal switch
during its on time, while a low side current limit prevents
the switch from turning on in the case of excessive off
phase current.
Step-Down Adaptive Control
Adaptive control of the output voltages achieves superior
system efficiency. When a given channel’s PWM pin is
low, the respective buck regulator output will go to a
programmable high output voltage. In this case the buck
will enter into a pulse-skipping mode since there is no load
connected. This guarantees that the buck output voltage
is high enough to immediately supply the LED current
once the string is reactivated. As soon as PWM goes
high, the output voltage of the buck will drop until there
is 1V across the LED current sink. This scheme ensures
the best efficiency for each LED channel. Since each LED
string is independently driven from a separate buck channel, efficiency is optimized for all three strings even if the
number of LEDs is mismatched between the channels.
Another benefit of this regulation method is that the LT3597
starts up with 10,000:1 dimming even if the PWM1-3 pulse
width is 1µs. Since VOUT starts up even if PWM1-3 is low,
the part achieves high dimming ratios with narrow pulse
widths within a couple of PWM1-3 clock cycles.
LED Current
Each LED string current can be individually programmed
up to a maximum of 100mA with a 2% matching accuracy
between the strings. An external resistor on the ISET1-3 pin
programs the max current for that string. The CTRL1-3
pin can be used for analog dimming. Digital PWM can be
programmed using the PWM1-3 pin. A dimming ratio of
10,000:1 can be achieved at a frequency of 100Hz.
Fault Protection and Reporting
The LT3597 protects against both open LED and shorted
LED conditions. If the LED1-3 pin voltage exceeds 12V
while the LED string is sinking current, or if the LED1-3
pin voltage is within 1.25V of VOUT1-3 pin voltage, the
channel is disabled until the fault is removed. If the LED
string opens, the LT3597 will limit the output to the voltage
set by the FB resistor divider.
The LT3597 reports a fault on the FAULT pin if any of the
LED strings is open or shorted. LED faults are only reported
if the respective string PWM signal is high. A fault is also
reported if the internal die temperature reaches the TSET
programmed derating limit.
3597f
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LT3597
APPLICATIONS INFORMATION
Inductor Selection
Inductor values between 100µH and 470µH are recommended 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.
Typically 10µF capacitors are sufficient for the VIN and BIAS
pins. The output capacitor for the buck regulators 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 (VLED = 3.5V)
SWITCHING FREQUENCY (kHz)
# LEDS
COUT (µF)
1000
1-3
3.3
>3
2.2
1-3
4.7
>3
3.3
1-3
15
>3
6.8
Table 1. Recommended Inductors
500
L (µH)
DCR (Ω)
CURRENT
RATING (A)
LPS6225
MSS1038
MSS1038
MSS1038
100
100
220
470
0.61
0.3
0.76
1.24
0.52
1.46
0.99
0.70
Coilcraft
www.coilcraft.com
CDRH105R
CDRW105R
CDRH105R
CDR6D28MN
100
220
470
100
0.253
0.50
1.29
0.9
1.35
0.94
0.60
0.75
Sumida
www.sumida.com
DS1262C2
DS1262C2
DS1262C2
100
220
470
0.17
0.35
1.243
1.5
1.0
0.7
Toko
www.toko.com
SLF10145T
SLF10145T
100
220
0.26
0.47
1.0
0.7
TDK
www.tdk.com
DR73
DR73
100
220
0.527
1.05
0.79
0.53
Coiltronics
www.cooperet.com
PART
VENDOR
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.
200
Diode Selection
Schottky diodes, with their low forward voltage drop and
fast switching speed, must be used for all LT3597 applications. Do not use P-N junction diodes. The diode’s
average current rating must exceed the application’s average 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 MAX REVERSE
(A)
VOLTAGE (V)
MANUFACTURER
DFLS160
B160
1
1
60
60
Diodes, Inc.
www.diodes.com
CMMSH1-60
1
60
Central
www.centralsemi.com
ESIPB
1
100
Vishay
www.vishay.com
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
3597f
11
LT3597
APPLICATIONS INFORMATION
Undervoltage Lockout (UVLO)
Programming Maximum LED Current
The EN/UVLO can be used to program the input UVLO
threshold by connecting it to a resistor divider from the
VIN pin as shown in Figure 2.
Maximum LED current can be programmed by placing a
resistor (RISET1-3) between the ISET1-3 pin and ground.
RISET1-3 values between 20k and 100k can be chosen to
set the maximum LED current between 100mA and 20mA
respectively.
LT3597
VIN
R2
The LED current is programmed according to the following equation:
EN/UVLO
R1
1.51V
+
–
3597 F02
Figure 2. EN/UVLO Control
Select R1 and R2 according to the following equation:
ILED1-3 = 2 •
(mA)
Table 5. LED Current Programming
RISET1-3 VALUE (kΩ)
LED CURRENT (mA)
20
100
25
80
33.3
60
50
40
100
20
In UVLO an internal 5.1µA pull-down current source is connected to the pin for programmable UVLO hysteresis. The
hysteresis can be set according to the following equation:
100
VUVLO(HYST) = 5.1µA • R2
80
LED CURRENT (mA)
Once the EN/UVLO pin falls below 0.4V, the part enters
into shutdown.
RISET1-3
See Table 5 and Figure 3 for resistor values and corresponding programmed LED current.
 R2 
VIN(UVLO) = 1.51V •  1+ 
 R1
Care must be taken if too much hysteresis is programmed,
the pin voltage might drop too far and cause the current
source to saturate.
1V
60
40
20
0
0
25
50
RSET1-3 (kΩ)
75
100
3597 F03
Figure 3. RISET1-3 Value for LED Current
3597f
12
LT3597
APPLICATIONS INFORMATION
LED Current Dimming
Two different types of dimming control are available with
the LT3597. The LED current can be dimmed using the
CTRL1-3 pin or the PWM1-3 pin.
For some applications, a variable DC voltage that adjusts
the LED current is the preferred method for brightness
control. In that case, the CTRL1-3 pin can be modulated
to set the LED dimming (see Figure 4). As the CTRL1-3 pin
voltage rises from 0V to 1.0V, the LED current increases
from 0mA to the maximum programmed LED current in a
linear fashion. As the CTRL1-3 pin continues to increase
past 1.0V, the maximum programmed LED current is
maintained. If this type of dimming control is not desired,
the CTRL1-3 pin can be tied to VREF .
120
LED CURRENT (mA)
100
80
60
40
20
0
0
0.25
0.5
0.75
1
CTRL1-3 (V)
1.25
1.5
3597 F04
Figure 4. LED Current vs CTRL1-3 Voltage
For True Color PWM dimming, the LT3597 provides up to
10,000:1 PWM dimming range at 100Hz. This is achieved
by allowing the duty cycle of the PWM1-3 pin to be reduced
from 100% to 0.01% for a PWM frequency of 100Hz (see
Figure 5), hence a minimum on-time of 1µs and a maximum period of 100ms. PWM duty cycle dimming allows
for constant LED color to be maintained over the entire
dimming range.
Using the TSET Pin for Thermal Protection
The LT3597 contains a special programmable thermal
regulation loop that limits the internal junction temperature. This thermal regulation feature provides important
protection at high ambient temperatures, and allows a
given application to be optimized for typical, not worstcase, ambient temperatures with the assurance that the
LT3597 will automatically protect 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 LT3597
linearly reduces the LED current, as needed, to maintain
this junction temperature. This can only be achieved when
the ambient temperature stays below the maximum programmed junction temperature. If the ambient temperature
continues to rise above the programmed maximum junction temperature, the LED current will reduce to less than
20% of the full current.
A resistor divider from the VREF pin programs the maximum
part junction temperature as shown in Figure 6.
tPWM
tON(PWM)
LT3597
PWM1-3
LED1-3
CURRENT
VREF
MAX ILED
R2
TSET
3597 F06
Figure 5. LED Current Using PWM Dimming
R1
3597 F07
Figure 6. Programming the TSET Pin
3597f
13
LT3597
APPLICATIONS INFORMATION
Table 6 shows commonly used values for R1 and R2.
Choose the ratio of R1 and R2 for the desired junction
temperature limit as described in Figure 7.
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.
0.8
TSET VOLTAGE (V)
0.7
0.6
0.5
LED Current Derating Using the CTRLM Pin
Another feature of the LT3597 is its ability to program a
derating curve for maximum LED current versus temperature. LED data sheets provide curves of maximum
allowable LED current versus temperature to warn against
exceeding this current limit and damaging the LED. The
LT3597 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
will fall below the internal 1V voltage reference, causing
LED currents to be controlled by the CTRLM pin voltage.
The LED current curve breakpoint and slope versus temperature are defined by the choice of resistor ratios and
use of temperature-dependent resistance in the divider
for the CTRLM pin.
0.4
0.3
–50
–25
75
0
25
50
TEMPERATURE (°C)
100
125
3597 F07
Figure 7. TSET Voltage for Temperature Derating
LT3597
VREF
RY
RY
R2
R1
(OPTION
A TO D)
CTRLM
RNTC
RNTC
A
B
RX
C
RX
RNTC
RNTC
D
3597 F08
Figure 8. Programming the CTRLM Pin
3597f
14
LT3597
APPLICATIONS INFORMATION
Table 7 shows a list of manufacturers/distributors of NTC
resistors. There are several other manufacturers available and the chosen supplier should be contacted for
more detailed information. If an NTC resistor is used to
indicate LED temperature, it is effective only if the resistor is placed as closely as possible 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 dependency of an NTC resistor can be nonlinear over a wide range of temperatures, it is important to
obtain a resistor’s exact value over temperature from the
manufacturer. Hand calculations of the CTRLM voltage can
then be performed at each given temperature, resulting in
the CTRLM versus temperature plotted curve. Iterations of
resistor value calculations may be necessary to achieve the
desired break point and slope of the LED current derating
curve. From the CTRLM voltage, the LED current can be
found using the curve shown in Figure 9.
Table 7. NTC Resistor Manufacturers/Distributors
Murata
www.murata.com
TDK Corporation
www.tdk.com
Digi-Key
www.digikey.com
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 voltage curve (CTRLM behavior) over temperature. Referred
to as the “Murata Chip NTC Thermistor Output Voltage
Simulator,” users can log onto www.murata.com and
download the software followed by instructions for creating 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 LT3597 can be programmed
between 200kHz and 1MHz by an external resistor connected between the RT pin and ground. Do not leave this
pin open. See Table 8 and Figure 10 for resistor values
and corresponding frequencies.
Table 8. RT Resistor Selection
SWITCHING FREQUENCY (MHz)
RT VALUE (kΩ)
1.0
33.2
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 temperature independent resistance to reduce the effects off the
NTC resistor over temperature.
100
1.0
SWITCHING FREQUENCY (MHz)
1.2
LED CURRENT (mA)
120
80
60
40
20
0
0
0.25
0.5
0.75
1
CTRLM (V)
1.25
1.5
3597 F09
Figure 9. LED Current vs CTRLM Voltage
0.5
80
0.2
220
0.8
0.6
0.4
0.2
0
25
50
75
100 125 150 175 200 225
RT (kΩ)
3597 F10
Figure 10. Programming Switching Frequency
3597f
15
LT3597
APPLICATIONS INFORMATION
Selecting the optimum switching frequency depends
on several factors. Inductor size is reduced with higher
frequency, but efficiency drops slightly due to higher
switching 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 hence 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.
Switching Frequency Synchronization
The nominal operating frequency of the LT3597 is programmed using a resistor from the RT pin to ground
over a 200kHz to 1MHz range. In addition, the internal
oscillator can be synchronized to an external clock applied
to the SYNC pin. The synchronizing clock signal input to
the LT3597 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 will 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.
The SYNC pin must be grounded if the clock synchronization 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, output voltage and maximum
input voltage. The advantage of high frequency operation
is smaller component sizes and values. The disadvantages
are lower efficiency and lower input voltage range for a
desired output voltage. The highest acceptable switching frequency (fSW(MAX)) for a given application can be
calculated as follows:
fSW(MAX) =
VD + VOUT
tON(MIN) ( VD + VIN − VSW )
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 (0.5V at max load). This equation
shows that slower switching is necessary to accommodate
high VIN /VOUT ratios. The reason the input voltage range
depends on the switching frequency is due to the finite
minimum switch on and off times. The switch minimum
on and off times are 200ns.
Adaptive Loop Control
The LT3597 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 PWM1-3 is low, the output of
the respective buck rises to a maximum value set by an
external resistor divider to the respective FB pin. Once
PWM1-3 goes high, the output voltage is adaptively reduced until the voltage across the LED current sink is 1V.
Figure 11 shows how the maximum output voltage can
be set by an external resistor divider.
LT3597
VOUT1-3
VOUT1-3
R2
FB1-3
R1
3597 F11
Figure 11. Programming Maximum VOUT1-3
3597f
16
LT3597
APPLICATIONS INFORMATION
The maximum output voltage must be set to exceed the
maximum LED drop plus 1V by a margin greater than 10%.
However, this margin must not exceed a voltage of 10V.
This ensures proper adaptive loop control. The equations
below are used to estimate the resistor divider ratio. The
sum of the resistors should be less than 100k to avoid
noise coupling to the FB pin.
)
 R2 
VOUT(MAX) = 1.1 VLED(MAX) + 1.1V = 1.2V •  1+ 
 R1
(
VOUT(MAX) = VLED(MAX) +1.1V +VMARGIN
VMARGIN ≤ 10V
Fault Flag
The FAULT pin is an open-collector output and needs an
external resistor tied to a supply. If the LED1-3 pin voltage exceeds 12V or if the LED1-3 pin voltage is within
1.25V of VOUT1-3 pins while PWM1-3 is high, the FAULT
pin will be pulled low. The FAULT pin will also be pulled
low if the internal junction temperature exceeds the TSET
programmed temperature limit.
There is a 3µs delay for FAULT flag generation when the
PWM1-3 signal is enabled to avoid generating a spurious
flag signal. The maximum current the FAULT can sink is
typically 1mA.
Minimum Input Voltage
Thermal Considerations
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:
VD + VOUT
DC =
VIN − VCESAT + VD
The LT3597 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. More power dissipation occurs in the
LT3597 at higher programmed LED currents. For 100mA
of LED current with a 100% PWM dimming ratio, at least
300mW is dissipated within the IC due to current sources.
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.
where VD is the Schottky forward drop and VCESAT is the
saturation voltage of the internal switch. The minimum
input voltage is:
 VD + VOUT(MAX) 
VIN(MIN) = 
 + VCESAT − VD
DCMAX

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.
In addition, the die temperature of the LT3597 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 LT3597. The maximum load
current should be derated as the ambient temperature approaches 125°C. The die temperature rise above ambient
is calculated by multiplying the LT3597 power dissipation
by the thermal resistance from junction to ambient. Power
dissipation within the LT3597 is estimated by calculating
the total power loss from an efficiency measurement and
subtracting 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.
3597f
17
LT3597
APPLICATIONS INFORMATION
Board Layout
As with all switching regulators, careful attention must be
paid to the PCB board 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 pin (SW). Always use a ground
plane under the switching regulator to minimize interplane coupling. Good grounding is essential in LED fault
detection.
Proper grounding is also essential for the external resistors
and resistor dividers that set critical operation parameters.
Both the LT3597 exposed pad and pin 18 are ground.
Resistors connected between ground and the CTRL1-3,
CTRLM, FB1-3, TSET, ISET1-3, RT and EN/UVLO pins are
best tied to pin 18 and not the ground plane.
3597f
18
LT3597
TYPICAL APPLICATIONS
48V 1MHz Triple Step-Down 100mA RGB LED Driver
VIN
48V
10µF
VIN
270k
BOOST2
0.1µF 100µH
EN/UVLO
SW2
BOOST1
DA2
SW1
FB2
DA1
VOUT2
LED2
BOOST3
91k
100µH
97k
R
2.2µF
0.1µF
9.1k
VCC
5V
97k
4.7k
B
3.3µF
FB1
LT3597
0.1µF 100µH
VOUT1
LED1
BIAS
10µF
2.2µF
33.2k
(1MHz)
3.83k
FB3
FAULT
PWM1-3
CTRL1-3
SYNC
RT
3
97k
DA3
100k
3
VOUT3
SW3
ISET1
VOUT3
LED3
VREF
ISET2
ISET3
GND
20k
20k
10k
TSET
CTRLM
3597 TA02
20k
82.5k
G
VREF
49.9k
100k
Efficiency
90
80
70
EFFICIENCY (%)
VOUT1
VOUT2
60
50
40
30
20
10
0
0
10 20 30 40 50 60 70 80 90 100
LED CURRENT PER CHANNEL (mA)
3597 TA02b
3597f
19
LT3597
TYPICAL APPLICATIONS
48V 1MHz Triple Step-Down 10W 100mA White LED Driver (3.6V LEDs)
VIN
48V
10µF
VIN
270k
BOOST2
0.1µF 100µH
EN/UVLO
SW2
BOOST1
DA2
SW1
FB2
DA1
VOUT2
LED2
BOOST3
91k
VOUT1
97k
2.2µF
100µH
0.1µF
97k
3.24k
2.2µF
3.24k
VCC
5V
VOUT2
FB1
LT3597
VOUT1
LED1
BIAS
10µF
2.2µF
33.2k
ISET1
VOUT3
LED3
VREF
ISET2
ISET3
20k
10k
TSET
GND CTRLM
3597 TA03
20k
97k
3.24k
FB3
FAULT
PWM1-3
CTRL1-3
SYNC
RT
3
VOUT3
DA3
100k
3
0.1µF 100µH
SW3
20k
82.5k
VREF
49.9k
100k
Efficiency
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0
10 20 30 40 50 60 70 80 90 100
LED CURRENT PER CHANNEL (mA)
3597 TA03b
3597f
20
LT3597
TYPICAL APPLICATIONS
24V 200kHz Triple Step-Down 100mA RGB LED Driver
VIN
24V
VIN
10µF
BOOST2
EN/UVLO
SW2
BOOST1
DA2
SW1
FB2
DA1
VOUT2
LED2
BOOST3
0.22µF
470µH
VOUT2
15µF
VOUT1
470µH
97k
9.1k
G
15µF
9.1k
FB1
LT3597
VOUT1
LED1
BIAS
10µF
3
VOUT3
15µF
97k
9.1k
FB3
220k
470µH
DA3
FAULT
PWM1-3
CTRL1-3
SYNC
RT
3
0.22µF
SW3
100k
ISET1
VOUT3
LED3
VREF
ISET2
ISET3
GND
B
VREF
TSET
CTRLM
3597 TA04
20k
20k
20k
Efficiency
90
80
70
EFFICIENCY (%)
R
0.22µF
97k
60
50
40
30
20
10
0
0
10 20 30 40 50 60 70 80 90 100
LED CURRENT PER CHANNEL (mA)
3597 TA04b
3597f
21
LT3597
TYPICAL APPLICATIONS
48V 1MHz Triple Step-Down 20mA RGB LED Driver
VIN
48V
10µF
VIN
270k
BOOST2
0.1µF 100µH
EN/UVLO
SW2
BOOST1
DA2
SW1
FB2
DA1
VOUT2
LED2
BOOST3
91k
VOUT1
R
2.2µF
100µH
97k
0.1µF
97k
4.7k
B
3.3µF
9.1k
VCC
5V
VOUT2
FB1
LT3597
0.1µF 100µH
VOUT1
LED1
BIAS
10µF
2.2µF
33.2k
3.83k
FB3
FAULT
PWM1-3
CTRL1-3
SYNC
RT
3
97k
DA3
100k
3
VOUT3
SW3
ISET1
VOUT3
LED3
VREF
ISET2
ISET3
GND
TSET
CTRLM
3597 TA05
100k
100k
100k
10k
82.5k
G
VREF
49.9k
100k
3597f
22
LT3597
PACKAGE DESCRIPTION
UHG Package
Variation: UHG52 (39)
52-Lead Plastic QFN (5mm × 8mm)
(Reference LTC DWG # 05-08-1846 Rev B)
43
41
39
6.40 REF
35 34 33 32 31 30 29 28
37
27
0.70 ± 0.05
44
26
25
24
46
5.50 ± 0.05
4.10 ± 0.05
23
48
22 3.20 REF
21
2.90 ±0.05
50
20
5.90 ±0.05
51
19
18
PACKAGE
OUTLINE
2
4
6
0.80 BSC
7
9
11 12
13 14 15 16
0.40 BSC
17
0.20 ± 0.05
7.10 ± 0.05
8.50 ± 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
51 50
48
46
44
R = 0.10
TYP
0.75 ± 0.05
5.00 ± 0.10
0.00 – 0.05
46
48
PIN 1 NOTCH
R = 0.30 TYP OR
0.35 × 45° CHAMFER
50 51
0.40 ±0.10
PIN 1
TOP MARK
(SEE NOTE 6)
43
43
41
41
39
39
7
37
37
9
35
35
6.40 REF
2
44
R = 0.10
TYP
2
4
4
6
6
7
9
34
34
11
33
33
12
32
32
12
13
31
31
14
30
30
13
14
15
29
29
16
28
17
27
28
27
8.00 ± 0.10
11
0.20 ± 0.05
0.80 BSC
0.60 TYP
0.40 BSC
15
5.90 ±0.10
2.90 ±0.10
16
17
0.70 TYP
0.200 REF
0.75 ± 0.05
26
25 24 23 22 21 20 19
18
(UHG39) QFN 0410 REV B
3.20 REF
BOTTOM VIEW—EXPOSED PAD
18 19 20 21 22 23 24 25 26
0.00 – 0.05
NOTE:
1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
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
3597f
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
23
LT3597
TYPICAL APPLICATION
Triple Step-Down RGB Single Pixel LED Driver, 100mA Current
VIN
48V
10µF
VIN
270k
BOOST2
0.1µF 100µH
EN/UVLO
SW2
BOOST1
DA2
SW1
FB2
DA1
VOUT2
LED2
BOOST3
91k
VOUT1
0.1µF
PWM
2V/DIV
97k
G
9.1k
3.3µF
9.1k
VCC
5V
10µF
VOUT2
3.3µF
100µH
97k
R
10,000:1 Dimming at 100Hz
FB1
LT3597
0.1µF 100µH
VOUT1
LED1
BIAS
10µF
VOUT3
SW3
3.3µF
200ns/DIV
97k
3597 TA06b
DA3
100k
9.1k
FB3
FAULT
PWM1:3
CTRL1:3
SYNC
RT
33.2k
ILED
50mA/DIV
ISET1
VOUT3
LED3
VREF
ISET2
ISET3
GND
TSET
CTRLM
3597 TA06
20k
20k
10k
20k
82.5k
B
VREF
49.9k
100k
RELATED PARTS
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
LT3492
60V, 2.1MHz 3-Channel (ILED = 1A) Full Featured LED
Driver
VIN: 3V to 30V (40VMAX), VOUT(MAX) = 60V, True Color PWM Dimming = 3000:1,
ISD < 1µA, 4mm × 5mm QFN-28 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, 2.5MHz 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
LT3596
60V, 1MHz 3-Channel Full Featured LED Driver
VIN: 6V to 60V, VOUT(MAX) = 40V, True Color PWM Dimming = 10,000:1,
ISD ≤ 2µA, 5mm × 8mm QFN-52 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 VIN: 3V to 30V, VOUT(MAX) = 44V, True Color PWM Dimming = 1000:1,
ISD < 1µA, 5mm × 5mm QFN-32 and TSSOP-28 Packages
Ballaster
LT3754
16-Channel x 50mA LED Driver with 60V Boost
Controller and PWM Dimming
VIN: 6V to 40V, VOUT(MAX) = 60V, True Color PWM Dimming = 3000:1,
ISD < 2µA, 5mm × 5mm QFN-52 Package
LT3760
8-Channel x 100mA LED Driver with 60V Boost
Controller and PWM Dimming
VIN: 6V to 40V, VOUT(MAX) = 60V, True Color PWM Dimming = 3000:1,
ISD < 2µA, TSSOP-28 Package
3597f
24 Linear Technology Corporation
LT 0311 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2011
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