LT3598IUFTRPBF [Linear]
6-String 30mA LED Driver with 1.5% Current Matching; 6串30毫安LED驱动器， 1.5 ％的电流匹配
| 型号： | LT3598IUFTRPBF |
| 厂家： | 
Linear |
| 描述： | 6-String 30mA LED Driver with 1.5% Current Matching |
| 文件： | 总24页 (文件大小：396K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT3598
6-String 30mA LED Driver
with 1.5% Current Matching
FEATURES
DESCRIPTION
TheLT®3598isafixedfrequencystep-upDC/DCconverter
designed to drive up to six strings of LEDs at an output
voltage up to 44V. LED dimming can be achieved with
analog dimming on the CTRL pin, and with pulse width
modulation dimming on the PWM pin. The LT3598
accurately regulates LED current even when the input
voltageishigherthantheLEDoutputvoltage.Theswitching
frequency is programmable from 200kHz to 2.5MHz
through an external resistor.
n
True Color PWM™ Dimming Delivers Up to 3000:1
Dimming Ratio
n
Drives Six Strings of LEDs at Up to 30mA
n
1.5% Accurate LED Current Matching
n
Wide Input Voltage Range: 3.2V to 30V
n
Output Voltage Up to 44V
n
Regulates Current Even When V > V
IN
OUT
n
n
n
n
n
n
n
n
Disconnects LEDs in Shutdown
Programmable Open LED Protection (Regulated)
OPENLED Alert Pin
Additional features include programmable overvoltage
protection, switching frequency synchronization to an
external clock, LED current derating based on junction
temperature and/or LED temperature, LED string disable
control, OPENLED alert pin and output voltage limiting
when all LED strings are disconnected. The LT3598 is
available in a thermally enhanced 24-lead (4mm × 4mm)
QFN and 24-lead TSSOP packages.
Programmable LED Current Derating
Adjustable Frequency: 200kHz to 2.5MHz
Synchronizable to an External Clock
Parallel Channels for Higher Current per LED String
Thermally Enhanced 4mm × 4mm QFN and 24-Lead
TSSOP Packages
APPLICATIONS
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. Protected by U.S. Patents, including 7199560, 7321203.
n
Notebook Computer Display
n
Medium Size Displays
n
Automotive LCD Display
TYPICAL APPLICATION
LED Current Matching
90% Efficient LED Driver for 60 White LEDs
PV
IN
10μH
8V TO 40V
1.5
ALL SIX LED STRINGS
2.2μF
4.7μF
1.0
SW
V
OUT
V
IN
V
V
O_SW
IN
5V
1.00M
30.9k
0.5
0
100k
2.2μF
OPENLED
SHDN
PWM
FB
SHDN
PWM
SYNC
–0.5
–1.0
–1.5
LT3598
SYNC
RT
51.1k
V
REF
10k
–50 –25
0
25
50
75 100 125
LED1
LED2
LED3
LED4
LED5
LED6
CTRL
TEMPERATURE (°C)
3598 TA01b
20mA
100k
T
I
V
C
SS
GND
SET SET
60.4k
10nF
2.61k
15nF
47pF
14.7k
100k
3598 TA01a
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1
LT3598
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
SHDN ................................................................V + 3V
IN
SW Voltage ...............................................................45V
V
, FB Voltage..........................................................6V
IN
REF
V , OPENLED...........................................................30V
I
, T .....................................................................6V
SET SET
Operating Junction Temperature Range
V
, V
Voltage .................................................44V
(Note 2)..................................................–40°C to 125°C
Maximum Junction Temperature........................... 125°C
Storage Temperature Range...................–65°C to 150°C
OUT O_SW
LED1 to LED6............................................................44V
PWM, SYNC, CTRL, RT, SS, V ...................................6V
C
TOP VIEW
TOP VIEW
1
2
V
IN
24
23
22
21
20
19
18
17
16
15
14
13
SW
OUT
SHDN
V
24 23 22 21 20 19
3
GND
V
O_SW
LED1
LED1
LED2
LED3
LED4
LED5
LED6
1
2
3
4
5
6
18
17
16
V
REF
4
V
REF
SS
RT
5
SS
LED2
LED3
LED4
LED5
LED6
6
RT
25
25
15 PWM
14 SYNC
13 NC
7
PWM
SYNC
NC
8
9
7
8
9 10 11 12
10
11
12
T
OPENLED
SET
FB
I
SET
V
C
CTRL
UF PACKAGE
24-LEAD (4mm s 4mm) PLASTIC QFN
FE PACKAGE
24-LEAD PLASTIC TSSOP
T
= 125°C, θ = 38°C/W
JMAX
JA
T
= 125°C, θ = 37°C/W
JA
JMAX
EXPOSED PAD (PIN 25) IS PGND, MUST BE SOLDERED TO PCB
EXPOSED PAD (PIN 25) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT3598EUF#PBF
LT3598IUF#PBF
LT3598EFE#PBF
LT3598IFE#PBF
TAPE AND REEL
PART MARKING*
3598
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3598EUF#TRPBF
LT3598IUF#TRPBF
LT3598EFE#TRPBF
LT3598IFE#TRPBF
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
24-Lead (4mm × 4mm) Plastic QFN
24-Lead (4mm × 4mm) Plastic QFN
24-Lead Plastic TSSOP
3598
LT3598
LT3598
24-Lead Plastic TSSOP
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/
3598fa
2
LT3598
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 5V, VSHDN = VIN unless otherwise noted. (Note 2)
PARAMETER
CONDITIONS
MIN
TYP
MAX
3.2
UNITS
Minimum Operating Voltage
Maximum Operating Voltage
Reference Voltage
3
V
V
30
1.216
1.210
1.230
0.01
1.260
1.260
V
V
l
Reference Voltage Line Regulation
3 < V < 30V, V = 0.3V
0.03
%/V
μA
IN
C
Maximum V Pin Current
Out of Pin
200
REF
FB Pin Bias Current
V
= 1.230V (Note 3)
100
300
600
1.24
21
250
nA
FB
FB Error Amp Transconductance
FB Error Amp Voltage Gain
FB Pin Voltage
ΔI = 5μA
μmhos
V/V
V
1.22
1.26
Current Loop Amp Transconductance
Current Loop Amp Voltage Gain
μmhos
V/V
μA
80
V Sink Current
C
10
Quiescent Current
V
V
V
= 5V, PWM = 0V, Not Switching
= 0V
3.5
0
5
1
mA
μA
SHDN
SHDN
CTRL
Quiescent Current in Shutdown
I
Voltage
= 1.5V, V
= 1.5V, R = 14.7kΩ
ISET
0.985
19.5
1.000
20
1.015
20.7
1.5
V
SET
TSET
LED Current
R
= 14.7kΩ
mA
%
ISET
l
LED String Current Matching
LED Open Detection Threshold
OPENLED Sink Current
20mA LED Current
0.5
0.2
2
0.25
V
mA
V
Minimum LED Regulation Voltage
LED1-6 Leakage Current
0.8
V
V
= 1V, V
= 5V, PWM = 0V
OUT
OUT
0.1
0.2
1
2
μA
μA
LED1-6
LED1-6
= 42V, V
= 44V, PWM = 0V
CTRL Pin Bias Current
Switching Frequency
V
= 0.8V (Note 4)
50
125
nA
CTRL
RT = 309kΩ
RT = 51.1kΩ
RT = 14.7kΩ
171
0.9
2.25
190
1
2.5
209
1.1
2.75
kHz
MHz
MHz
T
SET
Voltage
602
mV
Maximum Switch Duty Cycle
RT = 309kΩ
RT = 51.1kΩ
RT = 14.7kΩ
90
87
80
95
90
86
%
%
%
l
Switch Current Limit
(Note 5)
1.5
2
2.5
5
A
V
Switch V
I
= 0.5A
= 40V
0.12
0.2
CESAT
SW
Switch Leakage Current
V
SW
μA
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LT3598
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 5V, VSHDN = VIN unless otherwise noted. (Note 2)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
SHDN Pin Current
V
SHDN
V
SHDN
= 0V, V = 5V
0.1
30
1
60
μA
μA
IN
= 5V, V = 5V
IN
SHDN Voltage High
1.6
V
V
SHDN Voltage Low
0.4
15
Soft-Start Charging Current
PWM Input High Voltage
PWM Input Low Voltage
PWM Pin Bias Current
SYNC Input High Voltage
SYNC Input Low Voltage
SYNC Pin Bias Current
V
= 0.1V
5
1
10
μA
V
SS
0.4
1
V
PWM = 3.3V
0.1
μA
V
1.5
0.4
V
SYNC = 0V
SYNC = 3.3V
25
0.1
50
1
μA
μA
V
Switch Resistance
1000
Ω
O_SW
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 LT3598E 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
LT3598I is guaranteed over the full –40°C to 125°C operating junction
temperature range.
Note 3: Current flows out of FB pin.
Note 4: Current flows out of CTRL pin.
Note 5: Current limit guaranteed by design and/or correlation to static test.
Current limit is independent of duty cycle and is guaranteed by design.
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LT3598
TYPICAL PERFORMANCE CHARACTERISTICS
SHDN Pin Turn-On Threshold
SHDN Pin Current
Quiescent Current
6
5
4
1.5
1.4
1.3
1.2
50
45
40
35
30
25
20
15
10
5
125°C
–50°C
25°C
3
2
0
0
25
50
75 100 125
0
25
50
75 100 125
–50 –25
–50 –25
0
10
15
20
(V)
25
30
35
5
TEMPERATURE (°C)
TEMPERATURE (°C)
V
SHDN
3598 G03
3598 G01
3598 G02
Reference Voltage
Oscillator Frequency
Switch Current Limit
3.0
2.5
2.0
1.5
1.0
0.5
0
2.8
2.4
2.0
1.6
1.2
0.8
0.4
1.240
1.235
1.230
1.225
1.220
1.215
2.5MHz
V
= 40V
= 5V
IN
V
= 30V
IN
V
IN
1MHz
200kHz
0
25
50
75 100 125
0
25
50
75 100 125
0
25
50
75 100 125
–50 –25
–50 –25
–50 –25
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
3598 G05
3598 G06
3598 G04
Switch VCESAT
Soft-Start Pin Current
Feedback Pin Voltage
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
1.24
1.23
1.22
15.0
12.5
10.0
25°C
V
= 1.5V
C
125°C
V
= 1V
C
–50°C
1.21
1.20
7.5
5.0
0
25
50
75 100 125
–50 –25
0.25 0.50 0.75 1.00 1.25 1.5O
0
25
50
75 100 125
0
–50 –25
TEMPERATURE (°C)
SWITCH CURRENT (A)
TEMPERATURE (°C)
3598 G09
3598 G07
3598 G08
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LT3598
TYPICAL PERFORMANCE CHARACTERISTICS
LED Current vs PWM Duty Cycle
LED Current vs Temperature
LED Current vs CTRL Voltage
100
10
20.3
20.2
20.1
20.0
19.9
19.8
19.7
25
20
15
1
0.1
10
5
0.01
0.001
0
0
25
50
75 100 125
–50 –25
0.01
0.1
1
10
100
0
0.2
0.4
0.6
0.8
1.0
1.2
PWM DUTY CYCLE (%)
TEMPERATURE (°C)
CTRL VOLTAGE (V)
3598 G12
3598 G11
3598 G10
LED Current Matching
vs Temperature
LED Current Waveforms
(0.1% PWM)
OPENLED Sink Current
3.0
1.5
2.5
2.0
1.5
1.0
0.5
0
1.0
0.5
PWM
5V/DIV
SW
20V/DIV
0.0
I
L
1A/DIV
I
–0.5
–1.0
–1.5
LED1
50mA/DIV
3598 G15
20μs/DIV
0
25
50
75 100 125
0
25
50
75 100 125
–50 –25
–50 –25
TEMPERATURE (°C)
TEMPERATURE (°C)
3598 G14
3598 G13
LED Current Waveforms
(0.1% PWM)
LED Current Waveforms
(90% PWM)
LED Current Waveforms
(90% PWM)
PWM
5V/DIV
PWM
5V/DIV
PWM
5V/DIV
SW
20V/DIV
SW
20V/DIV
SW
20V/DIV
I
I
L
L
I
L
1A/DIV
1A/DIV
1A/DIV
I
I
LED1
50mA/DIV
LED1
50mA/DIV
I
LED1
50mA/DIV
3598 G16
3598 G18
3598 G17
2μs/DIV
5μs/DIV
100μs/DIV
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LT3598
PIN FUNCTIONS (QFN/TSSOP)
LED1-6 (Pins 1, 2, 3, 4, 5, 6/Pins 4, 5, 6, 7, 8, 9): LED
signal driving the PWM pin provides accurate dimming
control. The PWM signal can be driven from 0V to 5V. If
StringOutput.ConnectthebottomcathodeofeachLEDstring
to these pins. Tie pins to V
if the string is not used.
unused, the pin should be connected to V
.
OUT
REF
OPENLED (Pin 7/Pin 10): Open LED Flag When Any LED
String Opens. The output is open-collector. Tie a resistor
to other supply for open LED flag function.
RT (Pin 16/Pin 19): A resistor to ground programs
switching frequency between 200kHz and 2.5MHz. For
SYNCfunction,choosetheresistortoprogramafrequency
20% slower than the SYNC pulse frequency. Do not leave
this pin open.
I
(Pin8/Pin11):ProgramsLEDCurrentforEachString.
SET
Connecta14.7kresistorbetweenI andGNDtoprogram
SET
SS (Pin 17/Pin 20): Soft-Start Pin. Place a soft-start
capacitor here. Upon start-up, a 10μA current charges
the capacitor. Use a larger capacitor for slower start-up.
Leave open if not used.
each LED string current to 20mA. A 47pF capacitor on the
I
pin reduces current ripple in each LED string.
SET
CTRL (Pin 9/Pin 12): LED Current Control. If the CTRL
pin is not used, tie this pin to V
resistor.
through a 10k to 20k
REF
V
(Pin 18/Pin 21): Bandgap Voltage Reference.
REF
Internally set to 1.230V. This pin can supply up to 100μA.
CanbeusedtoprogramtheCTRLpinvoltageusingresistor
dividers to ground.
V (Pin 10/Pin 13): Error Amplifier Output Pin. Tie the
C
external compensation network to this pin.
FB (Pin 11/Pin 14): Feedback Pin for Overvoltage
Protection. Reference voltage is 1.230V. Connect the
GND (Pin 19/Pin 22): Ground. Tie directly to local ground
plane.
resistivedividertaphere.MinimizetraceareaatFB.SetV
OUT
SHDN (Pin 20/Pin 23): Shutdown Pin. Tie to 1.6V or more
to enable the device. Tie below 0.4V or less to disable
device. Do not float this pin.
according to V
= 1.230(1 + R2/R1) when overvoltage
OUT
protection occurs (see Figure 2).
T
(Pin 12/Pin 15): An external resistor divider from
SET
V
(Pin 21/Pin 24): Input Supply Pin. Must be locally
V
programs a decrease in LED current versus internal
IN
REF
bypassed with a capacitor to ground.
junction temperature (setting temperature breakpoint and
slope). If the T pin is not used, tie this pin to V
.
SET
REF
SW (Pin 22/Pin 1): Switch Pin. This is the collector of the
internal NPN power switch. Minimize the metal trace area
connected to this pin to minimize EMI.
NC (Pin 13/Pin 16): No Connection.
SYNC (Pin 14/Pin 17): Frequency Synchronization Pin.
Thisinputallowsforsynchronizingtheoperatingfrequency
to an external clock. The RT resistor should be chosen to
program a switching frequency 20% slower than SYNC
pulse frequency. This pin should be grounded if this
feature is not used.
V
(Pin 23/ Pin 2): Output Pin. This pin provides power
OUT
to all LEDs.
V
(Pin 24/ Pin 3): Drain of an Internal PMOS. The
O_SW
internal PMOS disconnects the feedback resistors from
the V pin during shutdown and the PWM transitioned
to low.
OUT
PWM (Pin 15/Pin 18): Input Pin for PWM Dimming
Control. Above 1V allows converter switching and below
Exposed Pad (Pin 25/ Pin 25): Ground. The Exposed Pad
must be soldered to the PCB.
1VdisablesswitchingwithV pinlevelmaintained.APWM
C
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LT3598
BLOCK DIAGRAM
V
RT
SYNC
SW
SHDN
IN
OSCILLATOR
1.230V
REF
SLOPE
+
–
S
R
3
Q1
Q
A2
V
C
SS
+
–
GND
GND
A3
V
OUT
PWM
PWM DIMMING
LOGIC
V
O_SW
+
–
OVP g
m
V
REF
FB
0.8V
+
–
LED g
m
CTRL
OPENLED
OPENLED DETECTION
T
SET
–
LED1
LED2
LED3
V
OUT
LED
A1
V
PTAT +
LED
DRIVE
DISABLE
DETECTION
LED4
LED5
CIRCUITRY
I
SET
LED6
3598 F01
Figure 1. Block Diagram
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LT3598
OPERATION
TheLT3598usesaconstant-frequency,peakcurrentmode
controlschemetoprovideexcellentlineandloadregulation.
Each string can drive up to 30mA with 1.5% matching ac-
curacybetweenstrings.Operationcanbebestunderstood
by referring to the Block Diagram in Figure 1.
is maintained on the external compensation capacitor.
This feature reduces transient recovery time. When the
PWM input again transitions high, the peak switch current
returns to the correct value.
The LT3598 uses the FB pin to provide overvoltage protec-
tion when all LED strings are open. There is an internal
LT3598 has a built-in boost converter which converts the
input voltage to a higher output voltage to drive LEDs.
The LED strings are connected to current sources where
the current level is set with an external resistor on the
PMOS switch between V
and V
that is controlled
OUT
O_SW
by the PWM signal. During the PWM off-period, this
PMOS is turned off, allowing for higher dimming range
and lower current during shutdown. A resistor divider is
I
pin. The LED1 to LED6 voltages are monitored for
SET
output voltage regulation. During normal operation, when
all LEDs are used, the lowest LED pin voltage (LED1 to
LED6) is used to regulate the output voltage to ensure all
LED strings have enough voltage to run the programmed
current.
connected between the V
pin and ground, which sets
O_SW
the overvoltage protection voltage.
If the LED1-6 pin voltage is below 0.2V (for a certain delay
after 80% of the programmed output voltage is reached),
the string is treated as an open LED string. As a result,
OPENLED lag is set. If a LED string is open in the middle
of the operation, the regulation will continue.
For any unused LED strings, tie their LED pins to V
.
OUT
An unused LED string is no longer in the regulation loop,
nor does it affect open LED detection. Never allow unused
LED strings to be left open.
OPENLED detection is disabled during the start-up phase
to avoid erratic flag generation. An LED string that is
The basic loop uses a pulse from an internal oscillator
to set the SR latch and turn on the internal power NPN
switchQ1. ThesignalatthenoninvertinginputofthePWM
comparator (A2 slope) is proportional to the sum of the
switch current and oscillator ramp. When slope exceeds
disabled by connecting its LED pin to V
is not an open
OUT
LED condition. During normal operation, if an LED string
is open and has the lowest LED pin voltage, the output
voltagewillregulateitselftofindanotherLEDstringthathas
the lowest LED pin voltage at about 0.8V. If the open LED
string has an LED voltage above 0.8V, the output voltage
will remain the same. When the LED string is open, it is
no longer in the regulation loop. The OPENLED detection
is active only when the PWM signal is enabled. To avoid
spurious OPENLED detection and high PWM dimming
ratio, more output capacitance is recommended to allow
V (the output of the g amplifier), the PWM comparator
C
m
resets the latch. The switch is then turned off, causing the
inductor current to lift the SW pin and turn on an external
Schottky diode connected to the output. Inductor current
flows via the Schottky diode charging the output capaci-
tor. The switch is turned on again at the next reset cycle
of the internal oscillator. During normal operation, the V
less voltage drop on V
.
C
OUT
voltage controls the peak switch current limit and, hence,
During start-up, 10μA of current charges the external
soft-start capacitor. The SS pin directly limits the rate of
the inductor current available to the output LEDs.
Dimming of the LEDs is accomplished by pulsing the LED
current using the PWM pin. When the PWM pin is low,
switching is disabled and the error amplifier is turned off
voltage rise on the V pin, which in turn, limits the peak
C
switch current. Soft-start also enables the switching
frequency foldback to provide a clean start-up for the
LT3598. Current limit protects the power switch and
external components.
so that it does not drive the V pin. Also, all internal loads
C
on the V pin are disabled so that the state of the V pin
C
C
3598fa
9
LT3598
APPLICATIONS INFORMATION
Inductor Selection
temperaturerangesthanotherdielectrics. A4.7μFto10μF
output capacitor is sufficient for most high output current
designs. Table 2 lists some suggested manufacturers.
Consult the manufacturers for detailed information on
their entire selection of ceramic parts.
Table 1 lists several inductors that work well with the
LT3598,however,therearemanyothermanufacturersand
devices that can be used. Consult each manufacturer for
detailed information on their entire range of parts. Ferrite
coreinductorsshouldbeusedtoobtainthebestefficiency.
Choose an inductor that can handle the necessary peak
current without saturating. Also, ensure that the inductor
has a low DCR (copper wire resistance) to minimize I R
powerlosses. Valuesbetween4.7μHand22μHwillsuffice
for most applications.
Table 2. Recommended Ceramic Capacitor Manufacturers
Taiyo Yuden
408-573-4150
www.t-yuden.com
2
AVX
843-448-9411
www.avxcorp.com
Murata
770-436-1300
www.murata.com
Inductor manufacturers specify the maximum current
rating as the current where inductance falls by a given
percentage of its nominal value. An inductor can pass a
current greater than its rated value without damaging it.
Consulteachmanufacturertodeterminehowthemaximum
inductor current is measured and how much more current
the inductor can reliably conduct.
Kemet
408-986-0424
www.kemet.com
United Chemi-Con
847-696-2000
www.chemi-con.com
Diode Selection
Schottky diodes, with their low forward voltage drop and
fast switching speed, must be used for all LT3598 applica-
tions. DonotuseP-Ndiodes. Table3listsseveralSchottky
diodes that work well. The diode’s average current rating
must exceed the application’s average output current.
The diode’s maximum reverse voltage must exceed the
application’s output voltage. A 2A diode is sufficient for
most designs. For PWM dimming applications, be aware
of the reverse leakage current of the diode. Lower leakage
current will drain the output capacitor less, allowing for
higherdimmingrange.ThecompaniesbelowofferSchottky
diodes with high voltage and current ratings.
Table 1. Recommended Inductors
MAX CURRENT
L
(μH)
DCR
(Ω)
RATING
(A)
PART
VENDOR
B1015AS-100M
#817FY-4R7M
1123AS-4R7M
10
4.7
4.7
0.07
0.06
0.12
2.2
2.26
1.90
TOKO
www.toko.com
74454068
74454010
7447745100
6.8
10
10
0.055
0.065
0.12
2.2
2
1.7
Würth Electronics
www.we-online.com
CDH74NP-120L
CDH74NP-150L
CDRH6D38-100
12
15
10
0.065
0.083
0.038
2.45
2.10
2.00
Sumida
www.sumida.com
IHLP-2525BD-01
10
4.7
4.7
0.129
0.056
0.200
2.5
1.83
1.8
Vishay
Table 3. Suggested Diodes
www.vishay.com
MAX
CURRENT
(A)
MAX REVERSE
VOLTAGE
(V)
SD25-4R7-R
Cooper
www.cooperet.com
PART
MANUFACTURER
LPS4018-472ML
Coilcraft
www.coilcraft.com
B250A
2
2
1
3
50
40
40
40
Diodes, Inc.
www.diodes.com
B240A
SBR140S3
SBM340, PDS340
Capacitor Selection
HSM150G
HSM150J
1
1
50
50
Microsemi
www.microsemi.com
Low ESR (equivalent series resistance) ceramic capaci-
tors should be used at the output to minimize the output
ripple voltage. Use only X5R or X7R dielectrics, as these
materials retain their capacitance over wider voltage and
SS3H9
3
90
Vishay
www.vishay.com
3598fa
10
LT3598
APPLICATIONS INFORMATION
Overvoltage Protection
The output voltage should be set higher than the normal
LED string operating voltage. Under normal operation,
LED1 to LED6 pin voltages are monitored and provide
feedback information to the converter for output volt-
age regulation given the programmed LED current. The
maximum output regulation loop is activated only when
all LEDs are open.
TheLT3598usestheFBpintoprovideregulatedovervoltage
protectionwhenallLEDstringsareopen.Aresistordivider
is connected between the V
pin and ground (Figure
O_SW
2). There is an internal PMOS switch between V
and
OUT
V
, which is controlled by the PWM signal. The PMOS
O_SW
switchadditionpreventsthefeedbackresistordividerfrom
draining the output capacitor during PWM off-period, al-
lowing for a higher dimming range without falsely tripping
the OPENLED flag. It also reduces the system current in
shutdown. This PMOS has about 1k resistance, so select
FB resistors taking this resistance into account.
Programming Maximum LED Current
Maximum LED current is programmed by placing a resis-
tor between the I pin and ground (R ). The I pin
SET
ISET
SET
resistor can be selected from 10k to 100k.
The LED current is programmed according to the follow-
ing equation:
To set the maximum output voltage, select the values
of R1 and R2 (see Figure 2) according to the following
equation:
294V
RISET
ILED
≈
R2
R1
⎛
⎜
⎝
⎞
V
OUT(MAX) = 1.230V 1+
⎟
⎠
See Table 4 and Figure 3 for resistor values and corre-
sponding programmed LED current.
LT3598
V
V
LED current can also be adjusted by programming the
CTRL pin voltage.
OUT
O_SW
R2
Table 4. RISET Value Selection for LED Current
FB
LED CURRENT (mA)
RESISTOR ON I PIN (k)
SET
R1
3mA
10mA
20mA
30mA
97.6
29.4
14.7
9.76
3598 F02
Figure 2. Overvoltage Protection
Voltage Feedback Connections
30
25
20
15
10
5
0
40
60
(k)
80
100
0
20
R
ISET
3598 F03
Figure 3. RISET Value Selection for LED Current
3598fa
11
LT3598
APPLICATIONS INFORMATION
LED Current Dimming
For True Color PWMTM dimming, the LT3598 provides up
to a 3000:1 PWM dimming range. This is achieved by
allowing the duty cycle of the PWM pin (connected to
the IC and an internal switch in series with the LED(s)),
to be reduced from 100% to as low as 0.1% for a PWM
frequency of 100Hz (Figure 6). PWM duty cycle dimming
allows for constant LED color to be maintained over the
entire dimming range.
Two different types of dimming control can be used with
the LT3598. The LED current can be set by modulating
the CTRL pin or the PWM pin.
For some applications, a variable DC voltage that adjusts
the LED current is the preferred method of brightness
control. The CTRL pin voltage can be modulated to set
the dimming of the LED string (see Figures 4 and 5). As
the voltage on the CTRL pin increases from 0V to 1.0V,
the LED current increases from 0 to the programmed LED
current level. As the CTRL pin voltage increases beyond
1V, it has no effect on the LED current.
For wide PWM dimming range, higher switching freq-
uency and lower PWM frequency configuration are
needed.Specialconsiderationsarerequiredforcomponent
selection and compensation network. Please contact
factory for optimized components selection if very high
dimming ratio is desired.
35
R
= 9.76k
ISET
True Color PWM is a registered trademark of Linear Technology Corporation.
30
25
20
15
10
5
V
REF
R2
R1
LT3598
CTRL
0
3598 F05
0.4 0.6 0.8
CTRL (V)
1
1.2
1.6
0
0.2
1.4
3598 F04
Figure 4. LED Current vs CTRL Voltage
Figure 5. LED Current vs CTRL
T
PWM
PWM
(= 1/f
)
PWM
TON
PWM
INDUCTOR
CURRENT
MAX I
LED
LED
CURRENT
3598 F06
Figure 6. LED Current Using PWM Dimming
3598fa
12
LT3598
APPLICATIONS INFORMATION
LED Current Derating Using the CTRL Pin
the manufacturer. Hand calculations of CTRL voltage can
then be performed at each given temperature, resulting
in the CTRL versus temperature plotted curve. Several
iterations of resistor value calculations may be required
to achieve the desired breakpoint and slope of the LED
current derating curve.
A useful feature of the LT3598 is its ability to program a
derating curve for maximum LED current versus tempera-
ture.LEDdatasheetsprovidecurvesofmaximum-allowable
LED current versus temperature to warn against exceed-
ing this current limit and damaging the LED. The LT3598
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 CTRL pin with a nega-
tive temperature coefficient using a resistor divider with
temperature dependent resistance (Figure 7). As ambient
temperatureincreases, theCTRLvoltagewillfallbelowthe
internal 1V voltage reference, causing LED currents to be
controlled by the CTRL pin voltage. The LED current curve
breakpoint and slope versus temperature is defined by the
choiceofresistorratiosanduseoftemperature-dependent
resistance in the divider for the CTRL pin.
Table 5. NTC Resistor Manufacturers/Distributors
Murata Electronics North America 770-436-1300
www.murata.com
TDK Corporation
516-535-2600
www.tdk.com
Digi-Key
800-344-4539
www.digikey.com
If calculating the CTRL voltage at various temperatures
gives a downward slope that is too strong, alternative
resistor networks can be chosen (B, C, D in Figure 7)
which use temperature independent resistance to reduce
the effects of the NTC resistor overtemperature.
Table 5 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 connected 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
nonlinearoverawiderangeoftemperatures,itisimportant
to obtain a resistor’s exact value over temperature from
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 (CTRL behavior) overtemperature. 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 creat-
ing an output voltage V
(CTRL) from a specified V
OUT
CC
supply (V ).
REF
R
R
Y
Y
V
REF
R2
LT3598
CTRL
R
R
R
R
R
NTC
R
X
NTC
NTC
X
NTC
R1
(OPTION A TO D)
A
B
C
D
3598 F07
Figure 7 . LED Current Derating vs Temperature Using NTC Resistor
3598fa
13
LT3598
APPLICATIONS INFORMATION
Using the T Pin for Thermal Protection
when the ambient temperature stays below the desired
maximum junction temperature. If the ambient tempera-
ture continues to rise past the programmed maximum
junction temperature, the LEDs current will be reduced
to approximately 5% of the full LED current.
SET
The LT3598 contains a special programmable thermal
regulationloopthatlimitstheinternaljunctiontemperature
of the part. Since the LT3598 topology consists of a single
boost converter with six linear current sources, any LED
string voltage mismatch will cause additional power to be
dissipatedinthepackage.Thistopologyprovidesexcellent
current matching between LED strings and allows a single
power stage to drive a large number of LEDs, but at the
priceofadditionalpowerdissipationinsidethepart(which
means a higher junction temperature). Being able to limit
the maximum junction temperature allows the benefits of
this topology to be fully realized. This thermal regulation
featureprovidesimportantprotectionathighambienttem-
peratures, and allows a given application to be optimized
for typical, not worst-case, ambient temperatures with the
assurance that the LT3598 will automatically protect itself
and the LED strings under worst-case conditions.
WhilethisfeatureisintendedtodirectlyprotecttheLT3598,
it can also be used to derate the LED current at high tem-
peratures. Since there is a direct relationship between the
LED temperature and LT3598 junction temperature, the
TSET function also provides some LED current derating
at high temperatures.
Two external resistors program the maximum IC junction
temperature using a resistor divider from the V pin, as
REF
shown in Figure 8. Choose the ratio of R1 and R2 for the
desired junction temperature. Figure 9 shows the relation-
ship of T voltage to junction temperature, and Table 6
SET
shows commonly used values for R1 and R2.
Table 6. TSET Junction Temperature
The operation of the thermal loop is simple. As the ambi-
ent temperature increases, so does the internal junction
temperature of the part. Once the programmed maximum
junction temperature is reached, the LT3598 begins to
linearly reduce the LED current, as needed, to try and
maintain this temperature. This can only be achieved
T (°C)
J
R1
R2
90
100k
100k
100k
100k
68.1k
63.4k
59k
100
110
120
54.9k
900
850
800
750
700
650
600
550
500
V
REF
R2
R1
LT3598
T
SET
3598 F08
Figure 8. Programming the TSET Pin
0
25
50
150
75
100
125
JUNCTION TEMPERATURE (°C)
3598 F09
Figure 9. TSET Pin Threshold
3598fa
14
LT3598
APPLICATIONS INFORMATION
Programming Switching Frequency
Switching Frequency Synchronization
The switching frequency of the LT3598 should be pro-
grammed between 200kHz and 2.5MHz by an external
resistorconnectedbetweentheRTpinandground. Donot
leave this pin open. See Table 7 and Figure 10 for resistor
values and corresponding frequencies.
The nominal operating frequency of the LT3598 is
programmed using a resistor from the RT pin to ground
and can be controlled over a 200kHz to 2.5MHz 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 LT3598 must have a frequency
between 240kHz and 3MHz, a duty cycle between 20%
and 80%, a low state below 0.4V and a high state above
1.5V. Synchronization signals outside of these parameters
willcauseerraticswitchingbehavior.Forproperoperation,
an RT resistor should be 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.
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. In addition, some applications require
very high duty cycles to drive a large number of LEDs from
a low supply. Low switching frequency allows a greater
operational duty cycle and, hence, a greater number of
LEDs to 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.
The SYNC pin should be grounded if the clock
synchronization feature is not used. When the SYNC pin
is grounded, the internal oscillator generates switching
frequency to the converter.
Table 7. Switching Frequency
SWITCHING FREQUENCY (MHz)
RT (k)
14.7
20.5
29.4
51.1
105
Soft-Start and Switching Frequency Foldback
2.5
2
For many applications, it is necessary to minimize the
inrush current at start-up. The LT3598’s soft-start circuit
significantly reduces the start-up current spike and output
voltage overshoot. Before the SS pin voltage reaches 1V,
the switching frequency will also fold back proportional
to the SS pin voltage. A typical value for the soft-start
capacitor is 10nF.
1.5
1
0.5
0.2
301
2.5
2.0
1.5
1.0
0.5
0
1000
10
100
(k)
R
T
3598 F10
Figure 10. Switching Frequency
3598fa
15
LT3598
APPLICATIONS INFORMATION
OPENLED FLAG
output capacitor are chosen based on performance, size
and cost. The compensation resistor and capacitor at V
C
The OPENLED pin is an open-collector output and needs
an external resistor tied to a supply (see Figure 11). If any
LEDstringisopenduringnormaloperation, theOPENLED
pin will be pulled down.
are selected to optimize control loop stability. For typical
LEDapplications,a15nFcompensationcapacitorinseries
with a 3k resistor at V is adequate.
C
The OPENLED flag is only activated after the first PWM
edge. The open LED detection is enabled only when the
PWM signal is enabled. There is a delay for OPENLED
flag generation when the PWM signal is enabled to avoid
generating a spurious flag signal. The maximum current
the OPENLED can sink is typically 2mA.
Thermal Considerations
The LT3598 provides six channels for LED strings with
internalNPNdevicesservingasconstant-currentsources.
WhenLEDstringsareregulated,thelowestLEDpinvoltage
is typically 0.8V. The higher the programmed LED current,
the more power dissipation in the LT3598. For 30mA LED
programming current with a 100% PWM dimming ratio,
at least 144mW is dissipated within the IC due to current
sources. If the forward voltages of the six LED strings are
verydissimilar, therecanbesignificantpowerdissipation.
Thermal calculations shall include the power dissipation
on current sources in addition to conventional switch DC
loss, switch AC loss and input quiescent loss. For best
efficiency, it is recommended that all channels have the
samenumberofLEDs,andeachstringhasasimilarvoltage
drop across the LEDs.
During start-up (see the Operation section), the open LED
detection is disabled. If an LED string is not used and tied
to V , the string will not be in any fault detection.
OUT
LT3598
R1
OPENLED
3598 F11
Figure 11. OPENLED Connection
Board Layout Considerations
As with all switching regulators, careful attention must be
paid to the PCB board layout and component placement.
To prevent electromagnetic interference (EMI) problems,
properlayoutofhighfrequencyswitchingpathsisessential.
Minimize the length and area of all traces connected to the
switchingnodepin(SW).Alwaysuseagroundplaneunder
the switching regulator to minimize interplane coupling.
Good grounding is essential in LED fault detection.
Loop Compensation
The LT3598 has an internal transconductance error
amplifier for LED current regulation whose V output
C
compensates the control loop. During an open LED
event where all LED strings are open, the V node also
C
compensates the control loop. The external inductor,
output capacitor, and the compensation resistor and
capacitor determine the loop stability. The inductor and
3598fa
16
LT3598
TYPICAL APPLICATIONS
LED Driver for 40 White LEDs with Two Channels Unused
L1
10μH
D1
PV
IN
6V TO 40V
C1
V
5V
C3
C2
4.7μF
IN
V
SW
V
OUT
2.2μF
IN
R6
V
O_SW
100k
2.2μF
R4
OPENLED
SHDN
PWM
1.00M
SHDN
FB
R5
30.9k
PWM
SYNC
SYNC
RT
LT3598
R1
51.1k
V
REF
R
HOT
LED1
LED2
LED3
LED4
LED5
LED6
10k
CTRL
20mA
R
100k
NTC
3598 TA02a
R8
60.4k
T
I
V
C
SS
GND
SET SET
C4
0.1μF
R
C
C5
47pF
2.61k
C
R7
100k
R3
14.7k
C
15nF
C1: TAIYO YUDEN GMK325BJ225ML
C2: MURATA GRM32ER71H475K
C3: TAIYO YUDEN LMK212BJ225MG
D1: DIODES, INC. B240A
L1: WÜRTH ELEKTRONIK 744777410
R
: MURATA NCP18WF104J03RB
NTC
Efficiency (PWM Dimming)
95
90
PV = 25V
IN
85
80
75
70
65
60
55
50
PV = 12V
IN
20 30 40 50 60
0
10
70 80 90
TOTAL LED CURRENT (mA)
3598 TA02b
3598fa
17
LT3598
TYPICAL APPLICATIONS
LED Driver for 30 White LEDs with 60mA Each String
L1
10μH
D1
PV
IN
6V TO 40V
C1
V
IN
C2
4.7μF
5V
V
SW
V
OUT
IN
2.2μF
R6
C3
2.2μF
V
O_SW
100k
R4
OPENLED
SHDN
CTRL
PWM
SYNC
RT
1.00M
SHDN
FB
CTRL
PWM
SYNC
R5
30.9k
LT3598
R1
51.1k
V
REF
R
HOT
LED1
LED2
LED3
LED4
LED5
LED6
10k
CTRL
60mA
R
100k
NTC
R8
60.4k
T
I
V
C
SS
GND
SET SET
C4
0.1μF
R
C
C5
47pF
2.61k
C
R7
100k
R3
9.76k
C
15nF
3598 TA03a
C1: TAIYO YUDEN GMK325BJ225ML
C2: MURATA GRM32ER71H475KA88L
C3: TAIYO YUDEN LMK212BJ225MG
D1: VISHAY SS3H9
L1: WÜRTH ELEKTRONIK 744777410
R
: MURATA NCP18WF104J03RB
NTC
Dimming Range (1000:1 PWM) at 125°C
Junction Temperature, 10ms Period
Efficiency (PWM Dimming)
100
95
90
85
80
75
70
65
60
PV = 25V
IN
PWM
5V/DIV
PV = 12V
IN
SW
20V/DIV
I
LED1
100mA/DIV
3598
2μs/DIV
40 60 80 100 120
140 160 180
0
20
TOTAL LED CURRENT (mA)
3598 TA03b
3598fa
18
LT3598
TYPICAL APPLICATIONS
Auto Battery Powered Driver for 20 LEDs with 90mA Each String
L1
4.7μH
D1
PV
IN
6V TO 40V
V
C2
4.7μF
C1
IN
V
SW
V
OUT
5V
C3
2.2μF
IN
2.2μF
V
100k
O_SW
R4
OPENLED
SHDN
CTRL
PWM
SYNC
RT
1.00M
SHDN
CTRL
PWM
FB
R5
30.9k
LT3598
R1
51.1k
V
REF
R10
20k
LED1
LED2
LED3
LED4
LED5
LED6
CTRL
90mA
R8
60.4k
T
I
V
C
SS
GND
SET SET
C4
0.1μF
R
C
C5
56pF
5.11k
C
R7
100k
R3
9.76k
C
6.8nF
3598 TA04a
C1: NIPPON CHEMI-CON KTS500B225M32NOTOO
C2: MURATA GRM32ER71H475KA88L
C3: TAIYO YUDEN LMK212BJ225MG
D1: VISHAY SS3H9
L1: WÜRTH ELEKTRONIK 7447785004
Dimming Range 1000:1 PWM,
10ms Period (125°C Junction Temperature)
Efficiency
95
90
PWM
5V/DIV
85
80
75
70
65
I
LED1
100mA/DIV
3598 TA04c
5μs/DIV
60
40 60 80 100 120
0
20
140 160 180
TOTAL LED CURRENT (mA)
3598 TA04b
3598fa
19
LT3598
TYPICAL APPLICATIONS
2 MHz LED Driver for 20 White LEDs
L1
10μH
D1
PV
IN
11.4V TO 12.6V
C1
2.2μF
V
C2
4.7μF
IN
3.2V TO 5.5V
C3
V
SW
V
OUT
IN
R6
V
O_SW
100k
2.2μF
R4
OPENLED
SHDN
PWM
2.4M
SHDN
FB
R5
140k
PWM
SYNC
SYNC
RT
LT3598
R1
21.5k
V
REF
R9
10k
LED1
LED2
LED3
LED4
LED5
LED6
CTRL
20mA
3598 TA02a
R8
T
I
V
C
SS GND
SET SET
107k
C6
100pF
C5
47pF
R7
178k
R3
14.7k
R
C
2k
C4
0.1μF
C
10nF
C
C1: MURATA GRM21BR71E225K
C2: MURATA GRM32ER71H475K
C3: TAIYO YUDEN LMK212BJ225MG
D1: DIODES, INC. SBR140S3
L1: TOKO 1123AS-100M
PWM Dimming (3000:1)
PWM
5V/DIV
I
L
200mA/DIV
I
LED, total
50mA/DIV
3598 TA07a
PV = 12V, V = 3.3V
IN
IN
1μs/DIV
3598fa
20
LT3598
TYPICAL APPLICATIONS
1 MHz LED Driver for 36 White LEDs
L1
10μH
D1
V
IN
5V
C2
4.7μF s 2
C1
2.2μF
V
SW
V
OUT
IN
R6
C3
1μF
V
O_SW
100k
R4
OPENLED
SHDN
PWM
2.4M
SHDN
FB
R5
76.8k
PWM
SYNC
SYNC
RT
LT3598
R1
53.6k
V
REF
R9
10k
LED1
LED2
LED3
LED4
LED5
LED6
CTRL
25mA
R8
107k
3598 TA07
T
I
V
C
SS
GND
SET SET
C4
0.1μF
C5
47pF
C6
100pF
R3
11.5k
R
C
3k
C
C
10nF
C1: MURATA GRM21BR71A225K
C2: MURATA GRM32ER71H475K
D1: DIODES, INC. SBR140S3
L1: VISHAY IHLP-2525BD-01
PWM Dimming (20μS Pulse Width)
PWM
5V/DIV
I
L
500mA/DIV
I
LED, total
50mA/DIV
3598 TA06
PV = V = 5V
IN
IN
5μs/DIV
3598fa
21
LT3598
PACKAGE DESCRIPTION
FE Package
24-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1771 Rev Ø)
Exposed Pad Variation AA
7.70 – 7.90*
3.25
(.128)
(.303 – .311)
3.25
(.128)
24 23 22 21 20 19 18 17 16 15 14 13
6.60 p0.10
2.74
(.108)
4.50 p0.10
6.40
(.252)
BSC
2.74
(.108)
SEE NOTE 4
0.45 p0.05
1.05 p0.10
0.65 BSC
5
7
8
1
2
3
4
6
9 10 11 12
RECOMMENDED SOLDER PAD LAYOUT
1.20
(.047)
MAX
4.30 – 4.50*
(.169 – .177)
0.25
REF
0o – 8o
0.65
(.0256)
BSC
0.09 – 0.20
(.0035 – .0079)
0.50 – 0.75
(.020 – .030)
0.05 – 0.15
(.002 – .006)
0.195 – 0.30
FE24 (AA) TSSOP 0208 REV Ø
(.0077 – .0118)
TYP
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS 4. RECOMMENDED MINIMUM PCB METAL SIZE
FOR EXPOSED PAD ATTACHMENT
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.150mm (.006") PER SIDE
MILLIMETERS
(INCHES)
2. DIMENSIONS ARE IN
3. DRAWING NOT TO SCALE
3598fa
22
LT3598
PACKAGE DESCRIPTION
UF Package
24-Lead Plastic QFN (4mm × 4mm)
(Reference LTC DWG # 05-08-1697)
0.70 ±0.05
4.50 ± 0.05
3.10 ± 0.05
2.45 ± 0.05
(4 SIDES)
PACKAGE OUTLINE
0.25 ±0.05
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
BOTTOM VIEW—EXPOSED PAD
R = 0.115
PIN 1 NOTCH
R = 0.20 TYP OR
0.35 × 45° CHAMFER
0.75 ± 0.05
4.00 ± 0.10
(4 SIDES)
TYP
23 24
PIN 1
TOP MARK
(NOTE 6)
0.40 ± 0.10
1
2
2.45 ± 0.10
(4-SIDES)
(UF24) QFN 0105
0.200 REF
0.25 ± 0.05
0.00 – 0.05
0.50 BSC
NOTE:
1. DRAWING PROPOSED TO BE MADE A JEDEC PACKAGE OUTLINE MO-220 VARIATION (WGGD-X)—TO BE APPROVED
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 0.15mm ON ANY SIDE, IF PRESENT
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
3598fa
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.
23
LT3598
TYPICAL APPLICATION
Efficiency vs Total LED Current
90% Efficient LED Driver for 60 White LEDs
PV
IN
8V TO 40V
D1
L1, 10μH
100
V
IN
C2
4.7μF
C1
2.2μF
5V
C3
V
SW
V
OUT
IN
95
90
85
80
75
70
65
60
V
V
= 25V
= 16V
100k
V
IN
O_SW
2.2μF
R4
OPENLED
SHDN
PWM
IN
1.00M
SHDN
FB
R5
30.9k
PWM
SYNC
SYNC
RT
LT3598
R1
51.1k
V
REF
R
HOT
LED1
LED2
LED3
LED4
LED5
LED6
10k
0
20
40
60
80
100
120
CTRL
TOTAL LED CURRENT (mA)
R
100k
NTC
3598 TA05b
20mA
R8
60.4k
T
I
V
C
SS
GND
SET SET
R
C4
10nF
C
2.61k
C5
47pF
R7
100k
R3
14.7k
C
C
3598 TA04a
15nF
RELATED PARTS
PART NUMBER
DESCRIPTION
36V, 1A (I ), 2MHz, Step-Down LED Driver
COMMENTS
V : 4V to 36V, V
LT3474/
LT3474-1
= 13.5V, True Color PWM Dimming = 400:1,
LED
IN
OUT(MAX)
OUT(MAX)
I
< 1μA, TSSOP-16E Package
SD
LT3475/
LT3475-1
Dual 1.5A (I ), 36V, 2MHz, Step-Down LED Driver
V : 4V to 36V, V
= 13.5V, True Color PWM Dimming = 3000:1,
LED
IN
I
< 1μA, TSSOP-20E Package
SD
LT3476
Quad Output 1.5A, 2MHz High Current LED Driver with V : 2.8V to 16V, V
= 36V, True Color PWM Dimming = 1000:1,
IN
OUT(MAX)
1000:1 Dimming
I
< 10μA, 5mm × 7mm QFN-10 Package
SD
LT3477
3A, 42V, 3MHz Boost, Buck-Boost, Buck LED Driver
V : 2.5V to 25V, V
= 40V, Dimming = Analog/PWM, I < 1μA,
IN
OUT(MAX) SD
QFN and TSSOP20E Packages
LT3478/LT3478-1 4.5A, 42V, 2.5MHz High Current LED Driver with 3000:1 V : 2.8V to 36V, V
= 42V, True Color PWM Dimming = 3000:1,
IN
OUT(MAX)
Dimming
I
< 3μA, TSSOP16E Package
SD
LT3486
Dual 1.3A, 2MHz High Current LED Driver
V : 2.5V to 24V, V
SD
= 36V, True Color PWM Dimming = 1000:1,
IN
OUT(MAX)
I
< 1μA, 5mm × 3mm DFN and TSSOP-16E Packages
LT3496
45V, 2.1MHz 3-Channel (I
LED Driver
= 1A) Full Featured
V : 3V to 30V (40V
), V
= 45V, True Color PWM Dimming =
OUT(MAX)
LED
IN
MAX
3000:1, I < 1μA, 4mm × 3mm QFN-28 Package
SD
LT3497
Dual 2.3MHz, Full Function LED Driver with Integrated
Schottkys and 250:1 True Color PWM Dimming
V : 2.5V to 10V, V
= 32V, I = 6mA, I < 12μA, 2mm × 3mm
Q SD
IN
OUT(MAX)
OUT(MAX)
DFN-10 Package
LT3498
2.3MHz, 20mA LED Driver and OLED Driver with
Integrated Schottky
V : 2.5V to 12V, V
= 32V, I = 1.65mA, I < 9μA, 2mm × 3mm
Q SD
IN
DFN-10 Package
LT3518/LT3517
LT3590
2.3A/1.3A 45V, 2.5MHz Full Featured LED Driver with
True Color PWM Dimming
V : 3V to 30V (40V
), V
= 42V, True Color PWM Dimming =
OUT(MAX)
IN
MAX
3000:1, I < 5μA, 4mm × 4mm QFN-16 Package
SD
48V, 850kHz 50mA Buck Mode LED Driver
36V, 2.2MHz, 500mA Buck Mode LED Driver
45V, 2.5MHz 16-Channel Full Featured LED Driver
V : 4.5V to 55V, Dimming = 200:1 True Color PWM, I < 15μA,
IN
SD
2mm × 2mm DFN-6 and SC70 Packages
LT3592
V : 3.6V to 36V, True Color PWM Dimming = 10:1, I < 1μA, 2mm × 3mm
IN
SD
DFN-10 and MSOP-10E Packages
LT3595
V : 4.5V to 55V, V
SD
= 45V, True Color PWM Dimming = 5000:1,
IN
OUT(MAX)
I
< 1μA, 5mm × 9mm QFN-56 Package
3598fa
LT 0309 REV A • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
24
●
●
© LINEAR TECHNOLOGY CORPORATION 2008
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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