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 V
OUT
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
LED Billboards and Signboards
Mono, Multi, Full-Color LED Displays
Large Screen Display LED Backlighting
Automotive, Industrial, and Medical Displays
LT3597
60V Triple Step-Down
LED Driver
DescripTion
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 be-
tween 200kHz and 1MHz. The frequency is also synchroniz-
able to an external clock. The LT3597 provides maximum
LED brightness while adhering to manufacturers’ speci-
fications 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 V
OUT
in order to achieve
optimal efficiency. Other features include: 2% LED cur-
rent matching between channels, open LED reporting,
shorted LED protection, programmable LED current, and
programmable temperature protection.
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.
applicaTions
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Typical applicaTion
Triple Step-Down RGB Single Pixel LED Driver, 100mA Current
V
IN
48V
10µF
270k
91k
BOOST1
V
OUT1
97k
R
9.1k
100µH
3.3µF
DA1
FB1
V
OUT1
LED1
BIAS
10µF
3
3
100k
FAULT
PWM1-3
CTRL1-3
SYNC
RT
33.2k
(1MHz)
I
SET1
20k
I
SET2
20k
I
SET3
20k
GND
LT3597
V
OUT2
LED2
BOOST3
0.1µF 100µH
SW3
3.3µF
DA3
FB3
V
OUT3
LED3
V
REF
T
SET
CTRLM
3597 TA01a
V
IN
EN/UVLO
BOOST2
0.1µF 100µH
SW2
3.3µF
DA2
FB2
9.1k
G
97k
V
OUT2
10,000:1 PWM Dimming at 100Hz
0.1µF
SW1
PWM
2V/DIV
V
OUT3
97k
9.1k
B
200ns/DIV
3597 TA01b
I
LED
50mA/DIV
V
CC
5V
10k
82.5k
49.9k
V
REF
100k
3597fa
1
LT3597
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
BST2
SW2
46
DA2
44
43 DA3
BST1 2
41 SW3
SW1 4
39 BST3
DA1 6
FB1 7
EN/UVLO 9
T
SET
11
V
REF
12
CTRLM 13
I
SET1
14
I
SET2
15
I
SET3
16
RT 17
18 19 20 21 22 23 24 25 26
LED1
LED2
LED3
V
OUT1
V
OUT2
V
OUT3
FAULT
GND
NC
53
GND
37 BIAS
35 FB3
34 FB2
33 CTRL1
32 CTRL2
31 CTRL3
30 PWM1
29 PWM2
28 PWM3
27 SYNC
V
IN
V
IN
Input Voltage (V
IN
), EN/UVLO ...................................60V
BOOST1-3 .................................................................85V
BOOST Pin Above SW Pin........................................ 25V
LED1-3, V
OUT1-3
........................................................42V
BIAS,
FAULT
..............................................................25V
V
REF
, RT, I
SET1-3
, T
SET
, 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
51 50
48
UHG PACKAGE
VARIATION: UHG52(39)
52-LEAD (5mm
×
8mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 32°C/W
EXPOSED PAD (PIN 53) IS GND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LT3597EUHG#PBF
LT3597IUHG#PBF
TAPE AND REEL
LT3597EUHG#TRPBF
LT3597IUHG#TRPBF
PART MARKING*
3597
3597
PACKAGE DESCRIPTION
52-Lead (5mm
×
8mm) Plastic QFN
52-Lead (5mm
×
8mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–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/
3597fa
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LT3597
elecTrical characTerisTics
PARAMETER
V
IN
Operating Voltage
Quiescent Current from V
IN
Minimum BIAS Voltage
Quiescent Current from BIAS
EN/UVLO = 0.4V
BIAS = 5V, Not Switching
BIAS = 0V, Not Switching, Current Out of Pin
0.4
1.47
EN/UVLO = 1.6V
EN/UVLO = 1.4V
FB = 6V
R
T
= 220k (200kHz)
R
T
= 33.2k (1MHz)
I
SW1-3
= 100mA
400
225
V
SW1-3
= 0V
I
SW1-3
= 100mA
R
T
= 220k
R
T
= 33.2k
170
900
1.6
R
T
= 220k
R
T
= 47k
V
SYNC
= 3.3V
(Note 4)
I
VREF
= 0µA
R
ISET1-3
= 20k, V
CTRL
= V
CTRLM
= T
SET
= 1.5V
V
TSET
= 1.0V
R
ISET1-3
= 20k
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 24V, BOOST = 29V, BIAS = 5V, EN/UVLO = 5V, PWM1-3 = 3.3V,
CTRL1-3 = CTRLM = T
SET
= 2.0V, V
OUT1-3
= 24V, SYNC = 0V, unless otherwise specified. (Note 2)
CONDITIONS
l
MIN
6
TYP
MAX
55
2
4
6
3.1
2
3
150
1.53
6
1.25
200
UNITS
V
µA
mA
mA
V
µA
mA
µA
V
V
nA
µA
V
nA
%
%
mV
EN/UVLO = 0.4V
BIAS = 5V, Not Switching
BIAS = 0V, Not Switching
2.1
4
3
2
60
0.7
1.51
10
5.1
1.22
95
85
265
510
280
2
200
1000
EN Threshold (Falling)
UVLO Threshold (Falling)
EN/UVLO Pin Current (Hysteresis)
FB1-3 Regulation Voltage
FB1-3 Pin Bias Current
Maximum Duty Cycle
Switch Saturation Voltage
Switch Current Limit
DA Pin Current to Stop OSC
Switch Leakage
BST1-3 Pin Current
Switching Frequency
SYNC Input Low
SYNC Input High
SYNC Frequency Range
SYNC Pin Bias Current
Soft-Start Time
V
REF
Voltage
Maximum V
REF
Current
I
SET1-3
Pin Voltage
T
SET
Voltage for LED Current Derating
T
SET
Pin Leakage Current
I
LED1-3
LED Current
4
1.15
90
78
700
350
700
230
1100
0.4
mA
mA
nA
mA
kHz
kHz
V
V
kHz
kHz
nA
ms
V
µA
V
mV
240
1000
200
2.5
1.96
200
2.0
1.0
540
2.04
200
98
97
100
100
102
103
nA
mA
mA
3597fa
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LT3597
elecTrical characTerisTics
PARAMETER
LED String Current Matching
LED Pin Voltage
LED1-3 Open Detection Threshold
LED1-3 Short Protection Threshold (from GND)
LED1-3 Short Protection Threshold (from V
OUT1-3
)
LED1-3 Pin Leakage Current
PWM1-3 Input Low Voltage
PWM1-3 Input High Voltage
PWM1-3 Pin Bias Current
CTRL1-3 Voltage for Full LED Current
CTRL1-3 Pin Bias Current
CTRLM Voltage for Full LED Current
CTRLM Pin Bias Current
FAULT
Output Voltage Low
FAULT
Pin Input leakage Current
CTRLM = 3V
I
FAULT
= 200µA
FAULT
= 25V
0.11
200
Note 3:
For Maximum Operating Ambient Temperature, see Thermal
Considerations in the Applications Information section.
Note 4:
Guaranteed by design.
CTRL1-3 = 6V
1.2
200
1.2
200
1.6
200
PWM1-3 = 3.3V
V
OUT1-3
= 6V
V
LED1-3
= 42V
10
1
1.25
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 24V, BOOST = 29V, BIAS = 5V, EN/UVLO = 5V, PWM1-3 = 3.3V,
CTRL1-3 = CTRLM = T
SET
= 2.0V, V
OUT1-3
= 24V, SYNC = 0V, unless otherwise specified. (Note 2)
CONDITIONS
R
ISET1-3
= 20k
l
MIN
TYP
±0.35
±0.35
1.1
0.28
MAX
±1.5
±2
UNITS
%
%
V
V
Adaptive V
OUT
Loop Enabled
15
2
200
0.4
V
V
nA
V
V
nA
V
nA
V
nA
V
nA
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.
3597fa
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LT3597
Typical perForMance characTerisTics
3.0
2.5
V
IN
CURRENT (mA)
2.0
1.5
1.0
0.5
0
25°C
T
A
= 25°C, unless otherwise noted.
V
IN
Quiescent Current
V
BIAS
= 5V
125°C
V
BIAS
CURRENT (mA)
3.0
2.5
2.0
1.5
1.0
0.5
0
V
BIAS
Quiescent Current
V
IN
= 24V
125°C
25°C
–40°C
CURRENT (µA)
Shutdown Current
2.00
V
IN
= 55V
V
BIAS
= 25V
1.75
1.50
1.25
1.00
0.75
0.50
0.25
I
VIN
I
BIAS
–25
0
25
50
75
TEMPERATURE (°C)
100
125
–40°C
0
10
20
30
40
V
IN
VOLTAGE (V)
50
60
3597 G01
–0.5
0
5
15
V
BIAS
VOLTAGE (V)
10
20
25
3597 G02
0
–50
3597 G03
UVLO Threshold Voltage (Falling)
1.8
1.7
1.6
UVLO VOLTAGE (V)
CURRENT (µA)
1.5
1.4
1.3
1.2
1.1
1.0
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
125
1
4
3
2
6
5
EN/UVLO Pin Bias Current
2.04
EN/UVLO = 1.4V
V
REF
Voltage
V
REF
LOAD = 0µA
2.03
2.02
V
REF
VOLTAGE (V)
2.01
2.00
1.99
1.98
V
IN
= 24V
V
IN
= 55V
V
IN
= 6V
0
–50
EN/UVLO = 1.6V
–25
75
0
25
50
TEMPERATURE (°C)
100
125
1.97
1.96
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
125
3597 G04
3597 G05
3597 G06
Switching Frequency
1.2
1.0
FREQUENCY (MHz)
0.8
0.6
0.4
0.2
0
–50
R
T
= 220k
R
T
= 33.2k
600
500
400
300
200
100
Current Limit
600
Switch Voltage Drop
V
BIAS
= 5V
125°C
25°C
–40°C
500
400
300
200
100
0
SWITCH
SWITCH VOLTAGE DROP (mV)
CURRENT (mA)
DA
–25
0
25
50
75
TEMPERATURE (°C)
100
125
0
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
125
0
50
100
150
200
SWITCH CURRENT (mA)
250
3597 G09
3597 G07
3597 G08
3597fa
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