LT3599EUHTRPBF [Linear]
4-Channel 120mA LED Driver with ±1.5% Current Matching; 4通道120毫安LED驱动器，具有± 1.5％的电流匹配
| 型号： | LT3599EUHTRPBF |
| 厂家： | 
Linear |
| 描述： | 4-Channel 120mA LED Driver with ±1.5% Current Matching |
| 文件： | 总26页 (文件大小：1400K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT3599
4-Channel 120mA LED Driver
with 1ꢀ5ꢁ Cꢂrrent Matching
FeaTures
n
DescripTion
True Color PWMTM Dimming Ratio Up to 3000:1
The LT®3599 is a fixed frequency 2A step-up DC/DC
converter designed to drive four strings of 120mA LEDs
up to a 44V output voltage. The switching frequency
is programmable from 200kHz to 2.1MHz through an
external resistor.
n
Drives Four Strings of LEDs at Up to 120mA
n
1ꢀ.% Accurate LED Current Matcꢁing
n
Wide Input Voltage Range: 3.1V to 30V
n
Output Voltage Up to 44V
n
Regulates LED Current Even When V > V
IN
OUT
LED dimming can be achieved with analog dimming on
the CTRL pin, and with pulse width modulation dimming
on the PWM pin. The LT3599 accurately regulates LED
current even when the input voltage is higher than the
LED output voltage.
n
n
n
n
n
n
n
n
n
Disconnects LEDs in Shutdown
Programmable Maximum V
(Regulated)
OUT
Open/Short LED Protection and Fault Flags
Programmable LED Current Derating
Adjustable Frequency: 200kHz to 2.1MHz
Synchronizable to an External Clock
Analog Dimming Up to 20:1
Programmable Input UVLO with Hysteresis
Thermally Enhanced 32-Pin (5mm × 5mm) QFN and
28-Pin TSSOP Packages
Additional features include programmable LED current
derating, switching frequency synchronization to an ex-
ternal clock, LED string disable control, OPENLED alert
pin, SHORTLED alert pins and programmable maximum
output voltage when all LED strings are disconnected.
The LT3599 is available in the thermally enhanced 32-pin
(5mm × 5mm) QFN and 28-pin TSSOP packages.
applicaTions
L, LT, LTC, LTM, Linear Technology and the Linear logo 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.
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Automotive Navigation TFT LCD Displays
Desktop and Notebook TFT LCD Displays
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Typical applicaTion
90% Efficient 12W LED Driver
10µH
PV
IN
8V TO 24V
4.7µF
s2
V
IN
3.3µF
3.1V TO 5.5V
LED Current Matcꢁing
V
IN
V
SW
V
OUT
IN
V
1.5
IN
1µF
V
O_SW
ALL FOUR LED STRINGS
100k
1M
100k
SHORTLED
OPENLED
1.0
0.5
200k
FB
SHDN/UVLO
PWM
31.6k
PWM
31.6k
33.2k
SYNC
LT3599
CTRL
RT
0
V
REF
53.6k
–0.5
–1.0
53.6k
T
SET
LED1
LED2
LED3
LED4
80.6k
–1.5
3599 TA01a
–50
0
25 50 75 100 125 150
TEMPERATURE (°C)
3599 TA01b
–25
DISABLE4
80mA PER STRING
I
V
SS
GND
47nF
SET
C
16.5k
100pF
10k
2.2nF
3599fd
ꢀ
LT3599
absoluTe MaxiMuM raTings (Note 1)
V , SHDN/UVLO, OPENLED, SHORTLED ..................30V
Operating Junction Temperature Range (Note 2)
LT3599E/LT3599I.............................. –40°C to 125°C
LT3599H............................................–40°C to 150°C
Maximum Junction Temperature
IN
SHDN/UVLO Pin Above V .........................................3V
IN
SW............................................................................45V
V
, V
..............................................................45V
OUT O_SW
LED1, LED2, LED3, LED4..........................................45V
PWM, SYNC, CTRL, FB, T , DISABLE4....................6V
LT3599E/LT3599I............................................. 125°C
LT3599H........................................................... 150°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, sec) (Note 5) .........300°C
SET
V , SS.........................................................................3V
C
V
, RT, I ..............................................................2V
REF
SET
pin conFiguraTion
TOP VIEW
TOP VIEW
1
2
V
IN
28
27
26
25
24
23
22
21
20
19
18
17
16
15
SW
OUT
SHDN/UVLO
NC
V
3
V
O_SW
LED1
32 31 30 29 28 27 26 25
4
GND
V
1
2
3
4
5
6
7
8
24 NC
23 NC
OUT
5
V
LED2
LED3
LED4
REF
V
O_SW
LED1
6
SS
GND
22
21
29
7
RT
LED2
LED3
LED4
V
REF
33
8
PWM
NC
20 SS
RT
DISABLE4
SHORTLED
NC
19
9
DISABLE4
18 PWM
17 SYNC
10
11
12
13
14
SYNC
NC
SHORTLED
OPENLED
NC
9
10 11 12 13 14 15 16
T
SET
FB
I
SET
V
C
CTRL
FE PACKAGE
UH PACKAGE
32-LEAD (5mm s 5mm) PLASTIC QFN
= 125°C, θ = 34°C/W
28-LEAD PLASTIC TSSOP
T
= 125°C, θ = 28°C/W , θ = 10°C/W
JA JC
EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB
T
JMAX
JMAX
JA
EXPOSED PAD (PIN 33) IS GND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LT3599EFE#PBF
LT3599IFE#PBF
LT3599HFE#PBF
LT3599EUH#PBF
LT3599IUH#PBF
TAPE AND REEL
PART MARKING*
LT3599FE
LT3599FE
LT3599FE
3599
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3599EFE#TRPBF
LT3599IFE#TRPBF
LT3599HFE#TRPBF
LT3599EUH#TRPBF
LT3599IUH#TRPBF
28-Lead Plastic TSSOP
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–40°C to 125°C
–40°C to 125°C
28-Lead Plastic TSSOP
28-Lead Plastic TSSOP
32-Lead (5mm × 5mm) Plastic QFN
32-Lead (5mm × 5mm) Plastic QFN
3599
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/
3599fd
ꢁ
LT3599
elecTrical characTerisTics Tꢁe l denotes tꢁe specifications wꢁicꢁ apply over tꢁe full operating
temperature range, otꢁerwise specifications are at TA = 2.°Cꢀ VIN = .V, VSHDN = .V, unless otꢁerwise notedꢀ (Note 2)
PARAMETER
CONDITIONS
MIN
TYP
MAX
3.1
UNITS
l
l
Minimum Operating Voltage
Maximum Operating Voltage
2.7
V
V
30
Reference Voltage V
I(V ) = 0µA
1.21
1.20
1.227
0.01
1.24
1.25
V
V
REF
REF
l
Reference Voltage Line Regulation
Maximum V Pin Current
I(V ) = 0µA, 3.1V < V < 30V
REF
0.03
100
%/V
µA
IN
(Note 3)
REF
V
Load Regulation
0 < I(V ) ≤ 100µA (Max)
1
1.223
100
200
210
50
mV
V
REF
REF
l
Feedback Voltage
1.196
1.250
250
FB Pin Bias Current
(Note 3)
nA
FB Error Amp Transconductance
FB Error Amp Voltage Gain
Current Loop Amp Transconductance
Current Loop Amp Voltage Gain
µmhos
V/V
µmhos
V/V
µA
∆I = 5µA
50
V Source Current (Out of Pin)
LED1-4 = 0.4V, FB = 1V, V = 1.5V
8
C
C
V Sink Current (OVP Mode)
C
LED1-4 = 0.4V, FB = 1.5V, V = 1.5V
15
µA
C
Quiescent Current
V
V
= 5V, PWM = 0V, Not Switching, V = 0.7V
3
4.8
1
mA
µA
SHDN
SHDN
C
Quiescent Current in Shutdown
LED Current
= 0V
0
R
= 13.3k
96
99
102
1.5
0.4
2.2
mA
%
ISET
l
LED String Current Matching
100mA LED Current
FB > 1.25V
0.25
0.3
1.5
0.77
0.1
100
LED Open Detection Threshold (V –GND)
V
LED
LED Short Detection Threshold (V –V
)
LED
0.8
V
OUT
LED Regulation Voltage
LED1-4 Leakage Current
CTRL Pin Bias Current
Switching Frequency
V
V
V
= 45V
1
µA
LED1-4
= 0.8V (Note 3)
200
nA
CTRL
R = 324k
176
0.9
1.82
198
1
2.06
220
1.1
2.3
kHz
MHz
MHz
T
T
T
R = 53.6k
R = 20k
T
Voltage
595
mV
SET
Maximum Switch Duty Cycle
R = 324k
97
85
70
98
90
80
%
%
%
T
l
R = 53.6k
T
R = 20k
T
Switch Current Limit
(Note 4)
2
2.5
0.10
0.2
3
A
V
Switch V
I
SW
= 0.5A
CESAT
Switch Leakage Current
V
= 45V, FB = 1.3V
5
µA
V
SW
SHDN/UVLO Pin Threshold (V
)
Shutdown
Rising
0.3
1.28
2.5
0.7
0.95
1.44
5.5
SD_SHDN
SHDN/UVLO Pin Threshold (V
)
1.36
V
SD_ UVLO
SHDN/UVLO Pin Hysteresis Current
SHDN = V
SHDN = V
– 50mV
+ 50mV
4
0
µA
µA
SD_UVLO
SD_UVLO
Soft-Start Current
SS = 1V (Note 3)
11
µA
V
PWM Input High Threshold
PWM Input Low Threshold
1
0.4
V
3599fd
ꢂ
LT3599
elecTrical characTerisTics Tꢁe l denotes tꢁe specifications wꢁicꢁ apply over tꢁe full operating
temperature range, otꢁerwise specifications are at TA = 2.°Cꢀ VIN = .V, VSHDN = .V, unless otꢁerwise notedꢀ (Note 2)
PARAMETER
CONDITIONS
MIN
TYP
MAX
2
UNITS
PWM Pin Bias Current
SYNC Input High Threshold
SYNC Input Low Threshold
SYNC Pin Bias Current
PWM = 3.3V
0.1
µA
V
1.7
0.8
V
SYNC = 0V (Note 3)
SYNC = 3.3V
25
0.1
50
1
µA
µA
V
Switch Resistance
1000
Ω
mA
mA
V
O_SW
OPENLED Pull-Down Current
SHORTLED Pull-Down Current
DISABLE4 Input High Threshold
DISABLE4 Input Low Threshold
PWM = 5V; LEDx < 0.2V, OPENLED = 0.3V
PWM = 5V, SHORTLED = 0.3V
1
1
1.15
0.4
V
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 3: Current flows out of pin.
Note 4: Current limit guaranteed by design and/or correlation to static test.
Current limit is independent of duty cycle and is guaranteed by design.
Note .: TSSOP package only.
Note 2: The LT3599E 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
LT3599I is guaranteed over the full –40°C to 125°C operating junction
temperature range.
3599fd
ꢃ
LT3599
Typical perForMance characTerisTics TA = 2.°C unless otꢁerwise specified
SHDN/UVLO Pin Turn-On
Tꢁresꢁold (VSD_UVLO
SHDN/UVLO Pin
)
(Hysteresis) Current
VIN Current (Sꢁutdown)
500
450
400
350
300
250
200
150
100
50
1.45
1.40
1.35
1.30
1.25
6
5
4
3
2
1
0
JUST BEFORE PART TURN-ON
V
= 30V
IN
V
= 3V
IN
AFTER PART TURN-OFF
25 50 75 100 125 150
JUNCTION TEMPERATURE (°C)
0
0
25 50 75 100 125 150
–50 –25
0
25 50 75 100 125 150
0
–50 –25
–50 –25
JUNCTION TEMPERATURE (°C)
JUNCTION TEMPERATURE (°C)
3599 G01
3599 G02
3599 G03
VREF
Switcꢁing Frequency
Switcꢁing Frequency vs RT
3.0
2.5
2.0
1.5
10000
1000
100
1250
1240
1230
1220
1210
2.1MHz
V
= 30V
= 3V
IN
V
1MHz
IN
1.0
0.5
0
0.2MHz
50
100 125 150
0
25 50 75 100 125 150
–50 –25
0
25
75
10
100
1000
–50 –25
R
T
(k)
JUNCTION TEMPERATURE (°C)
JUNCTION TEMPERATURE (°C)
3599 G04
3599 G05
3599 G06
TSET Pin Tꢁresꢁold
LED Current vs CTRL Pin
Soft-Start Pin Current
vs Junction Temperature
120
13
900
850
800
750
700
650
600
550
500
I
= 13.3k
SET
100
80
60
40
20
0
12
11
10
9
8
7
0
25 50 75 100 125 150
–50 –25
0
0.2
0.4
0.6
0.8
1.0
1.2
0
25
50
150
75
100
125
JUNCTION TEMPERATURE (°C)
JUNCTION TEMPERATURE (°C)
CTRL PIN VOLTAGE (V)
3599 G07
3599 G08
3599 G09
3599fd
ꢄ
LT3599
Typical perForMance characTerisTics TA = 2.°C unless otꢁerwise specified
VC Pin Active and Clamp Voltages
LED Current vs PWM Duty Cycle
Switcꢁ Saturation Voltage
2500
2000
1500
1000
500
100
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
V
HIGH
C
10
1
V
ACTIVE
C
0.1
0
0.01
0
0.5
1
1.5
(A)
2
2.5
0
25 50 75 100 125 150
–50 –25
0.01
0.1
1
10
100
PWM DUTY CYCLE (%)
I
JUNCTION TEMPERATURE (°C)
SW
3599 G10
3599 G12
3599 G11
LED Current vs Temperature
Switcꢁ Current Limit
Feedback Pin Voltage
2.8
1250
1245
1240
1235
1230
1225
1220
1215
1210
1205
1200
101
100
99
2.4
2.0
1.6
1.2
0.8
0.4
98
97
0
25 50 75 100 125 150
50
–25
JUNCTION TEMPERATURE (°C)
125 150
0
25 50 75 100 125 150
JUNCTION TEMPERATURE (°C)
–50 –25
–50
0
25
75
–50 –25
100
JUNCTION TEMPERATURE (°C)
3599 G13
3599 G15
3599 G14
LED Current Waveforms
(0ꢀ1% PWM) (10ms Period)
LED Current Waveforms
(90% PWM) (10ms Period)
PWM
5V/DIV
PWM
5V/DIV
SW
20V/DIV
SW
20V/DIV
I
LED1
50mA/DIV
I
LED1
50mA/DIV
3599 G16
3599 G17
2µs/DIV
100µs/DIV
3599fd
ꢅ
LT3599
pin FuncTions
CTRL: LED Current Control. If the CTRL pin is not used,
SHDN/UVLO: The SHDN/UVLO pin has an accurate 1.36V
threshold and can be used to program an undervoltage
lockout (UVLO) threshold for system input supply using a
resistor divider from supply to ground. A 4µA pin current
hysteresis allows programming of undervoltage lockout
(UVLO) hysteresis. 1.36V turns the part on and removes a
4µA sink current from the pin. SHDN/UVLO = 0V reduces
tie this pin to V
.
REF
DISABLE4: Allows Disabling Channel 4. Connect to V
REF
to disable channel 4. If channel 4 is disabled, the LED4 pin
should be connected to the LED3 pin. Connect DISABLE4
to ground to allow operation of channel 4.
Exposed Pad: Ground. The ground for the IC should be
soldered to a continuous copper ground plane under the
LT3599 die.
V current<0.1µA.SHDN/UVLOcanbedirectlyconnected
IN
to V . Do not leave this pin open.
IN
SHORTLED: Indicates a high side short (LED pin shorted
FB: Feedback Pin for Overvoltage Protection. Reference
to V ). This is an open-collector output.
OUT
voltage is 1.223V. Connect the resistive divider tap here.
SS: Soft-Start Pin. Place a soft-start capacitor here. Upon
start-up,a11µAcurrentchargesthecapacitor.Usealarger
capacitor for a slower start-up.
Minimize trace area at FB. Set V
according to V
=
OUT
OUT
1.223(1 + R2/R1) when overvoltage protection occurs.
GND: Analog Ground. Tie directly to local ground plane.
Connect RT, I and T resistors between this local
SW: Switch Pin. This is the collector of the internal NPN
power switch. Minimize the metal trace area connected
to this pin to minimize EMI.
SET
SET
ground plane and their respective pins.
I
: Programs Led Current for Each String. A resistor
SET
SYNC:FrequencySynchronizationPin.Thisinputallowsfor
to ground programs LED currents between 30mA and
synchronizingtheoperatingfrequencytoanexternalclock.
120mA.
The R resistor should be chosen to program a switching
T
LED1-4: LED String Output. Connect the bottom cathode
of each LED string to these pins.
frequency 20% slower than SYNC pulse frequency. This
pin should be grounded if this feature is not used.
OPENLED:OpenLEDFlag. Anopen-collectoroutputwhen
T
: Programs LT3599 junction temperature breakpoint,
SET
any LED string opens.
beyond which LED currents will begin to decrease. An
internal V threshold (see Block Diagram) increases
PTAT
NC: No Connect Pins. Can be left open or connected to
any ground plane.
with junction temperature. When V
exceeds T pin
SET
PTAT
voltage, LED currents are decreased. If the function is not
PWM: Input Pin for PWM Dimming Control. Above 1V
required, connect T pin to V pin. If the T pin is
SET
REF
SET
allows converter switching, and below 0.4V disables
not used, tie this pin to V
.
REF
switching with V pin level maintained. A PWM signal
C
V : Error Amplifier Output Pin. Tie the external compensa-
tion network to this pin.
C
driving the PWM pin provides accurate dimming control.
The PWM signal can be driven from 0V to 5V. If unused,
the pin should be connected to V
.
V : Input Supply Pin. Must be locally bypassed with a
capacitor to ground.
REF
IN
RT: A Resistor to Ground Which Programs Switching
Frequency Between 200kHz and 2.1MHz. For SYNC func-
tion, choose the resistor to program a frequency 20%
slower than the SYNC pulse frequency. Do not leave this
pin open.
V
: Drain of an Internal PMOS. The internal PMOS
O_SW
disconnects the feedback resistors from the V
pin
OUT
during shutdown and when the PWM pin is low.
V
V
: Output Pin. This pin provides power to all LEDs.
OUT
:BandgapVoltageReference.Internallysetto1.227V.
REF
This pin can supply up to 100µA. Can be used to program
the CTRL pin voltage using resistor dividers to ground.
3599fd
ꢆ
LT3599
block DiagraM
V
RT
SYNC
SW
SHDN/UVLO
IN
–
+
OSCILLATOR
1.4V
1.227 V
REF
SLOPE
SOFT-START LOGIC
+
–
S
R
3
Q1
Q
A2
V
C
+
–
SS
A3
–
V
OUT
PWM
PMOS
PWM DIMMING
LOGIC
V
O_SW
+
–
V
REF
R2
R1
OVP g
m
V
REF
FB
0.7V
+
LED g
m
CTRL
1V
–
+
–
SHORTLED
OPENLED
OPENLED, SHORTLED
DETECTION
LED1
LED2
LED3
LED4
T
SET
–
LED DRIVE
CIRCUITRY
A1
V
+
PTAT
DISABLE4
I
LED4 DISABLE
SET
GND
3599 F01
Figure 1ꢀ Block Diagram
3599fd
ꢇ
LT3599
operaTion
TheLT3599usesaconstant-frequency,peakcurrentmode
control scheme to provide excellent line and load regula-
tion. Operation can be best understood by referring to the
Block Diagram in Figure 1.
the peak switch current limit and, hence, the inductor
current available to the output LEDs.
DimmingoftheLEDsisaccomplishedbyeitherPWMdim-
ming or analog dimming. PWM dimming is achieved by
pulsing the LED current using the PWM pin. For constant
color LED dimming, the LT3599 provides up to a 3000:1
widePWMdimmingrangebyallowingthedutycycleofthe
PWM pin to be reduced from 100% to as low as 0.033%.
When the PWM pin is low, switching is disabled and the
To turn on the LT3599, the V pin must exceed 3.1V and
IN
the SHDN/UVLO pin must exceed 1.4V. The SHDN/UVLO
pin threshold allows programming of an undervoltage
lockout (UVLO) threshold for the system input supply us-
ing a simple resistor divider. A 4µA current flows into the
SHDN/UVLO pin before the part turns on and is removed
after the part turns on. This current hysteresis allows the
programming of hysteresis for the UVLO threshold. See
“ShutdownPinandProgrammingUndervoltageLockout”
intheApplicationsInformationsection.Forpartswitching,
the PWM pin must exceed 1V (typical). For micropower
error amplifier is turned off so that it does not drive the V
C
pin. Also, all internal loads on the V pin are disabled so
C
that the state of the V pin is maintained on the external
C
compensation capacitor. This feature reduces transient
recovery time. When the PWM input again transitions
high, the peak switch current returns to the correct value.
In applications where the user can sacrifice OPENLED,
SHORTLED fault flag diagnostics, the dimming ratios can
be as high as 3000:1. Analog dimming of LED currents is
accomplished by varying the level of CTRL pin voltage.
This method, however, changes LED color since dimming
isachievedbychangingLEDcurrent. ForCTRLpinvoltage
less than 1V, LED current is defined as:
shutdown, the SHDN/UVLO pin at 0V reduces V supply
current to approximately ~0µA.
IN
LT3599 has a built-in boost converter which converts the
input voltage to a higher output voltage for driving LEDs.
The LED strings are connected to current sources where
the current level is set with an external resistor on the
I
pin. The LED1 to LED4 voltages are monitored for
SET
output voltage regulation. During normal operation, when
all LEDs are used, the lowest LED pin voltage (LED1 to
LED4) is used to regulate the output voltage to ensure all
LED strings have enough voltage to run the programmed
current.
1330
R
ILED = VCTRL
•
Amps
(
)
ISET
The LT3599 uses the FB pin to provide overvoltage protec-
tion when all LED strings are open. There is an internal
PMOS switch between V
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
If the user prefers only three strings, then LED string 4 can
be disabled through the DISABLE4 pin and by connecting
LED4 to any other LED pin. If the user prefers only two
strings,thentwopinsareconnectedinparallel(i.e.,LED1,2
and LED3,4 can be connected together in operation).
and V
that is controlled
OUT
O_SW
connected between the V
the overvoltage protection voltage.
pin and ground, which sets
O_SW
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) is proportional to the sum of the switch
current and oscillator ramp. When this signal exceeds the
IftheLED1-4pinvoltageisbelow0.3V, thestringistreated
as an open LED string. As a result, an OPENLED flag is
set. If a LED string is opened during regular operation,
the output voltage will regulate to the optimum voltage
for the remaining connected strings.
V voltage, the PWM comparator resets the latch. The
C
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 capacitor. The switch
is turned on again at the next reset cycle of the internal
If a short occurs between V
and any LED pin during
OUT
operation, the LT3599 immediately turns off the shorted
channel and sets a SHORTLED flag. Disabling the channel
protects the LT3599 from high power thermal dissipation
and ensures reliable operation.
oscillator.Duringnormaloperation,theV voltagecontrols
C
3599fd
ꢈ
LT3599
operaTion
SHORTLED and OPENLED detection are disabled during
the start-up phase to avoid false flag generation. If an LED
string is open during normal operation, it will no longer
be used to regulate the output voltage. The output voltage
will regulate itself to find the LED string with the lowest
LED pin voltage. Fault detection (SHORTLED, OPENLED)
is updated when the PWM pin is high and latched when
the PWM pin is low.
During start-up, 11µA of current charges the external
soft-start capacitor. The SS pin directly limits the rate
of voltage rise on the V pin, which in turn, limits the
C
peak switch current. Soft-start also enables switching
frequency foldback to provide a clean start-up for the
LT3599. Switch current limit protects the power switch
and external components.
applicaTions inForMaTion
Inductor Selection
Capacitor Selection
Table 1 lists several inductors that work well with the
LT3599,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
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
temperature ranges than other dielectrics. A 4.7µF to 10µF
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.
2
has a low DCR (copper wire resistance) to minimize I R
powerlosses. Valuesbetween4.7µHand22µHwillsuffice
for most applications.
Table 2ꢀ Recommended Ceramic Capacitor Manufacturers
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.
Taiyo Yuden
(408) 573-4150
www.t-yuden.com
AVX
(843) 448-9411
www.avxcorp.com
Murata
Kemet
(770) 436-1300
www.murata.com
(408) 986-0424
www.kemet.com
Table 1ꢀ Recommended Inductors
Diode Selection
L
MAX DCR CURRENT
PART
(µH)
(Ω)
RATING (A)
VENDOR
Schottky diodes, with their low forward voltage drop and
fast switching speed, should be used for all LT3599 ap-
plications. Table 3 lists several Schottky diodes that work
well. The diode’s average current rating must exceed the
application’saverageoutputcurrent.Thediode’smaximum
reverse voltage must exceed the application’s output volt-
age. 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 higher dimming range.
B1015AS-100M
817FY-4R7M
10
0.07
0.06
2.2
TOKO
4.7
2.26
www.toko.com
744065100
74454068
74454010
10
6.8
10
0.04
0.055
0.065
3
2.2
2
Würth Electronics
www.we-online.com
CDH115-100
CDH74NP-120L
CDH74NP-150L
10
12
15
0.028
0.065
0.083
3
2.45
2.10
Sumida
www.sumida.com
IHLP2020-BZ
IHLP2525-BD
10
10
0.184
0.116
2.3
2.5
Vishay
www.vishay.com
3599fd
ꢀ0
LT3599
applicaTions inForMaTion
The companies below offer Schottky diodes with high
voltage and current ratings. Standard silicon diodes (PN
junction diodes) should not be used.
The output voltage should be set 10% higher than the
normal LED string operating voltage. Under normal
operation, LED1 to LED4 pin voltages are monitored and
provide feedback information to the converter for output
voltage regulation given the programmed LED current.
The output voltage regulation loop is activated only when
all LEDs are open.
Table 3ꢀ Suggested Diodes
MAX
CURRENT
(A)
MAX REVERSE
VOLTAGE
(V)
PART
MANUFACTURER
B250A
DFLS240
B240A
B350A
B340A
2
2
2
3
3
50
40
40
50
40
Diodes, Inc.
www.diodes.com
Programming Maximum LED Current
Maximum LED current can be programmed by placing a
resistor between the I pin and ground (R ). The I
SET
ISET
SET
HSM150G
HSM150J
HSM350G
1
1
3
50
50
50
Microsemi
www.microsemi.com
pin resistor can be selected from 11k to 44.2k.
The LED current can be programmed according to the
following equation:
Overvoltage Protection
The LT3599 uses the FB pin to provide overvoltage protec-
tion. A resistor divider is connected between the V
1330
RISET
ILED
≈
Amps (CTRL >1V)
(
)
O_SW
pin and ground (Figure 2). There is an internal PMOS
switch between V and V , which is controlled by
See Table 4 and Figure 3 for resistor values and corre-
sponding programmed LED current.
OUT
O_SW
the PWM signal. The PMOS switch addition prevents the
feedback resistor divider from draining the output capaci-
tor during PWM off-period, allowing 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 resistor values taking
this resistance into account.
LED current can also be adjusted by programming the
CTRL pin voltage.
Table 4ꢀ RISET Value Selection for LED Current
LED CURRENT (mA)
30mA
RESISTOR ON I PIN (k)
SET
44.2
26.7
13.3
11
50mA
99mA
To set the maximum output voltage, select the values
of R1 and R2 (see Figure 2) according to the following
equation:
120mA
R2
R1
120
100
80
60
40
20
0
VOUT(MAX) =1.223V 1+
LT3599
V
V
OUT
O_SW
R2
FB
R1
0
20
60 80 100 120 140 160
(k)
40
R
ISET
3599 F03
3599 F02
Figure 2ꢀ Overvoltage Protection Voltage Feedback Connections
Figure 3ꢀ RISET Value Selection for LED Current
3599fd
ꢀꢀ
LT3599
applicaTions inForMaTion
LED Current Dimming
low as 0.033% at a PWM frequency of 100Hz (Figure 6).
Dimming by PWM duty cycle, allows for constant LED
color to be maintained over the entire dimming range.
Two different types of dimming control can be used with
theLT3599.TheLEDbrightnesscanbeseteitherbyanalog
dimming(CTRLpinvoltageadjustmentbetween0Vand1V)
or PWM dimming (PWM pin duty cycle adjustment).
For LT3599 PWM dimming control during startup and
normal operation, observe the following guidelines:
Forsomeapplications,thepreferredmethodofbrightness
control is to use a variable DC input voltage. The CTRL
pin voltage can be adjusted to set the dimming of the LED
string (see Figures 4 and 5). As the voltage on the CTRL
pin increases from 0V to 1V, the LED current increases
from 0 to the programmed LED current level. Once the
CTRL pin voltage increases beyond 1V, it has no effect on
the LED current.
(1) STARTUP
LT3599 V
start-up requires the SHDN/UVLO pin to be
OUT
asserted from off to on and the PWM on-time to be above
a minimum value. The lowest PWM on-time allowed for
fault detection is ≈20µs. The lowest PWM on-time allowed
for reaching V
regulation is typically 20µs but might be
OUT
greaterdependingonexternalcircuitparameters.OnceLED
current is in regulation, PWM on-time can be reduced as
low as 3µs depending on external component selection.
For True Color PWM dimming, the LT3599 provides
up to a 3000:1 PWM dimming range by allowing the duty
cycle of the PWM pin to be reduced from 100% to as
(2) V
Collapse
OUT
If during normal operation V
or because PWM on-time is too low, a re-start is required
(see STARTUP in item (1)).
collapses due to a fault
OUT
120
I
= 13.3k
SET
100
80
60
40
20
0
V
REF
R2
R1
LT3599
CTRL
0
0.2
0.4
0.6
0.8
1.0
1.2
3599 F05
CTRL PIN VOLTAGE (V)
3599 F04
Figure 4ꢀ LED Current vs CTRL Voltage
Figure .ꢀ LED Current vs CTRL
T
PWM
PWM
(= 1/f
)
PWM
TON
PWM
INDUCTOR
CURRENT
MAX I
LED
LED
CURRENT
3599 F06
Figure 6ꢀ LED Current Using PWM Dimming
3599fd
ꢀꢁ
LT3599
applicaTions inForMaTion
PROGRAMMING LED CURRENT DERATING
vs TEMPERATURE
temperature dependency of an NTC resistor can be non-
linear over a wide range of temperatures, it is important
to obtain a resistor’s exact values over temperature from
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.
Programming LED Current Derating Using tꢁe CTRL Pin
A useful feature of the LT3599 is its ability to program
a derating curve for maximum LED current versus tem-
perature. LED data sheets provide curves of maximum-
allowable LED current versus temperature to warn against
exceeding this current limit and damaging the LED. The
LT3599 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 negative temperature coefficient using a resistor divider
with temperature dependent resistance (Figure 7). As the
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 .ꢀ 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.
A variety of resistor networks and NTC resistors with
different temperature coefficients can be used for pro-
gramming CTRL to achieve the desired CTRL curve vs
temperature.
Murata Electronics provides a selection of NTC resistors
with complete data over a wide range of temperatures.
In addition, a software tool is available which allows the
user to select from different resistor networks and NTC
resistorvalues, and then simulate the exact output voltage
curve (CTRL behavior) over temperature. Referred to as
the “Murata Chip NTC Thermistor Output Voltage Simula-
tor,” users can log onto www.murata.com/designlib and
download the software followed by instructions for creat-
Table 5 shows a list of manufacturers/distributors of NTC
resistors. There are several other manufacturers avail-
able 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
ing an output voltage V
(CTRL) from a specified V
OUT
CC
supply (V ). At any time during the selection of circuit
REF
parameters, the user can access data on the chosen NTC
resistor by clicking on a link to the Murata catalog.
R
Y
R
Y
V
REF
R2
LT3599
CTRL
R
NTC
R
R
X
R
NTC
R
NTC
R
X
NTC
R1
(OPTION A TO D)
A
B
C
D
3599 F07
Figure 7 ꢀ LED Current Derating vs Temperature Using NTC Resistor
3599fd
ꢀꢂ
LT3599
applicaTions inForMaTion
Using tꢁe T Pin for Tꢁermal Protection
Two external resistors program the maximum IC junction
SET
temperature using a resistor divider from the V pin, as
REF
The LT3599 contains a special programmable thermal
regulationloopthatlimitstheinternaljunctiontemperature
of the part. Since the LT3599 topology consists of a single
boost converter with four 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 LT3599 will automatically protect itself
and the LED strings under worst-case conditions.
shown in Figure 8. Choose the ratio of R1 and R2 for the
desired junction temperature. Table 6 shows commonly
used values for R1 and R2 (see T graph).
SET
Table 6ꢀ Resistor Values to Program Maximum IC Junction
Temperature
T (°C)
R1 (k)
80.6
82.5
82.5
84.5
84.5
84.5
90.9
R2 (k)
53.6
53.6
51.1
51.1
49.9
44.2
44.2
J
100
105
110
115
120
135
145
Programming Switcꢁing Frequency
The switching frequency of the LT3599 is set between
200kHz and 2.1MHz by an external resistor connected
between the RT pin and ground (see Table 7). Do not
leave this pin open.
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 LT3599 begins to
linearly reduce the LED current, as needed, to try and
maintain this temperature. This can only be achieved
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.
Selecting the optimum switching frequency depends
on several factors. Inductor size is reduced with higher
frequency, but efficiency drops due to higher switching
losses.Inaddition,someapplicationsrequireveryhighduty
cycles to drive a large number of LEDs from a low supply.
Lowswitchingfrequencyallowsagreateroperationalduty
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.
WhilethisfeatureisintendedtodirectlyprotecttheLT3599,
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 LT3599 junction temperature, the
Table 7ꢀ Switcꢁing Frequency
T
function also provides some LED current derating
SET
at high temperatures.
SWITCHING FREQUENCY (MHz)
R (k)
T
2.1
2.0
1.5
1.0
0.5
0.4
0.3
0.2
20
V
REF
21.5
31.6
53.6
121
154
210
324
R2
LT3599
T
SET
R1
3599 F08
Figure 8ꢀ Programming tꢁe TSET Pin
3599fd
ꢀꢃ
LT3599
applicaTions inForMaTion
Switcꢁing Frequency Syncꢁronization
flowsintotheSHDN/UVLOpin.Afterthepartturnson,0µA
flows from the SHDN/UVLO pin. Calculation of the on/off
thresholds for a system input supply using the LT3599
SHDN/UVLO pin can be made as follows :
The nominal operating frequency of the LT3599 is pro-
grammed using a resistor from the RT pin to ground
and can be controlled over a 200kHz to 2.1MHz 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 LT3599 must have a frequency
between 240kHz and 1.5MHz, a pulse on-time of at least
150ns, a pulse off-time of at least 300ns, a low state below
0.8V and a high state above 1.7V. Synchronization signals
outside of these parameters will cause erratic switching
R1
R2
VS(OFF) =1.4 1+
VS(ON) = VS(OFF) +(4µA •R1)
Asimpleopendraintransistorcanbeaddedtotheresistor
divider network at the SHDN/UVLO pin to independently
control the turn off of the LT3599.
behavior. For proper operation, an R resistor should be
T
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.
WiththeSHDN/UVLOpinconnecteddirectlytotheV pin,
IN
aninternalundervoltagelockoutthresholdofapproximately
2.7V exists for the V pin. This prevents the converter
IN
from operating in an erratic mode when supply voltage is
TheSYNCpinshouldbegroundediftheclocksynchroniza-
tion feature is not used. When the SYNC pin is grounded,
the internal oscillator generates switching frequency to
the converter.
too low. The LT3599 provides a soft-start function when
recovering from such faults as SHDN < 1.4V and/or V
IN
< 2.7V. See “Soft-Start” in the Applications Information
section for details.
Sꢁutdown and Programming Undervoltage Lockout
Soft-Start and Switcꢁing Frequency Foldback
The LT3599 has an accurate 1.4V shutdown threshold
at the SHDN/UVLO pin. This threshold can be used in
conjunction with a resistor divider from the system input
supply to define an accurate undervoltage lockout (UVLO)
threshold for the system (Figure 10). A pin current hys-
teresis allows programming of the hysteresis voltage for
this UVLO threshold. Just before the part turns on, 4µA
To limit inrush current and output voltage overshoot dur-
ing start-up/recovery from a fault condition, the LT3599
providesasoft-startpin,SS.TheSSpinisusedtoprogram
switchcurrentramp-uptimingusingacapacitortoground.
TheLT3599monitorssystemparametersforthefollowing
faults: V < 2.7V or SHDN < 1.4. On detection of any of
IN
these faults, the LT3599 stops switching immediately and
10000
1000
100
V
S
LT3599
R1
SHDN/UVLO
11
–
ON
+
1.4V
OFF
R2
4µA
10
100
1000
3599 F11
RT (k)
3599 F10
Figure 10ꢀ Programming Undervoltage
Lockout (UVLO) witꢁ Hysteresis
Figure 9ꢀ Switcꢁing Frequency
3599fd
ꢀꢄ
LT3599
applicaTions inForMaTion
a soft-start latch is set causing the SS pin to be discharged
(see the Soft-Start Pin Timing Diagram in Figure 11). All
faults are detected internally and do not require external
components. When all faults no longer exist and the SS
pin has been discharged to at least 0.25V, the soft-start
latch is reset and an internal 11µA supply charges the SS
pin. During start-up or recovery from a fault, the SS pin
ramp up controls the ramp up of switch current limit.
Soft-start ramp rate is given by:
but continues to ramp upwards. If the soft-start ramp
voltage was held every time PWM goes low, this would
cause very slow start-up of LED displays for applications
using very high PWM dimming ratios.
OPENLED FLAG
The OPENLED pin is an open-collector output and needs
an external resistor tied to a supply (see Figure 12). If any
LED string is open during normal operation, the OPENLED
pin will be pulled down.
∆VSS ISS
=
I =11µA typ
(
SS
)
∆T
CSS
The open LED detection is enabled only when the PWM
signalisenabled.ThereisadelayforOPENLEDflaggenera-
tion when the PWM signal is enabled to avoid generating
a spurious flag signal.
A 10nF capacitor from the SS pin to ground will therefore
provide a 1V/ms ramp rate on the SS pin.
In addition, during soft-start, switching frequency is re-
duced to protect the inductor from high currents.
During start-up (see the Operation section), the open LED
detection is disabled.
SW
SHORTLED FLAG
The SHORTLED pin is an open-collector output, and needs
SS
FAULTS TRIGGERING
an external resistor tied to a supply (see Figure 12). If
SOFT-START LATCH
0.3V (ACTIVE THRESHOLD)
WITH SW TURNED OFF
0.25V (RESET THRESHOLD)
any LED pin is shorted to V
during normal operation,
OUT
IMMEDIATELY:
0.15V
the SHORTLED pin will be pulled down. In addition, the
shorted LED string (channel) is immediately disabled,
thereby protecting the LT3599.
V
IN
< 2.7V
OR
SOFT-START
LATCH RESET:
SS < 0.25V
AND
SOFT-START
LATCH SET
SHDN < 1.4V
V
> 2.7V
AND
IN
The short LED detection is enabled only when the PWM
signal is enabled. There is a delay for SHORTLED flag gen-
eration when the PWM signal is enabled to avoid spurious
signal being generated.
SHDN > 1.4V
AND
PWM > 1V (FOR >200ns)
3599 F12
Figure 11ꢀ Soft-Start Pin Timing Diagram
During start-up, the SHORTLED flag is disabled (see the
Operation section).
A useful feature of the LT3599 is that it waits for the first
PWMpinactivehigh(minimum200nspulsewidth)before
LT3599
it allows the soft-start of V pin to begin. This feature
C
R1
R2
ensures that during start-up of the LT3599 the soft-start
ramp has not timed out before PWM is asserted high.
Without this ‘wait for PWM high’ feature, systems which
OPENLED
SHORTLED
apply PWM after V and SHDN are valid, can potentially
IN
turn on without soft-start and experience high inductor
currents during wake up of the converter’s output voltage.
It is important to note that when PWM subsequently goes
low, the soft-start ramp is not held at its present voltage
3599 F13
Figure 12ꢀ OPENLED and SHORTLED Connection
3599fd
ꢀꢅ
LT3599
applicaTions inForMaTion
Loop Compensation
programming current with a 100% PWM dimming ratio,
at least 280mW is dissipated within the IC due to current
sources. 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 same number of LEDs, and each string has a
similar voltage drop across the LEDs.
The LT3599 has an internal transconductance error
amplifier for LED current regulation whose V output
C
compensates the control loop. During overvoltage, the
V node also compensates the control loop. The external
C
inductor, output capacitor, and the compensation resistor
and capacitor determine the loop stability. The inductor
and output capacitor are chosen based on performance,
size and cost. The compensation resistor and capacitor
Board Layout Considerations
at V are selected to optimize control loop stability. For
C
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 es-
sential. Minimize the length and area of all traces con-
nected 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. Recommended component placement is
shown in Figure 13.
typical LED applications, a 10nF compensation capacitor
in series with a 2k resistor at V is adequate.
C
Tꢁermal Consideration
The LT3599 provides four channels for LED strings with
internalNPNdevicesservingasconstant-currentsources.
When LED strings are regulated, the lowest LED pin volt-
age is 0.7V. The higher the programmed LED current, the
more power dissipation in the LT3599. For 100mA LED
BYPASS
CAPACITOR
SOLDER EXPOSED PAD (PIN 29)
TO THE ENTIRE COPPER GROUND
POWER V
IN
PLANE UNDERNEATH THE DEVICE.
GROUND
CONNECT MULTIPLE GROUND PLANES
THROUGH VIAS UNDERNEATH THE IC
INDUCTOR
LT3599
SW
V
SCHOTTKY DIODE
POWER
GROUND
V
C
VIN
1
2
28
IN
OUT
27 SHDN/UVLO
C
OUT
3
4
26 NC
V
O_SW
LED1
LED2
LED3
LED4
25 GND
V
C
5
REF
24
23
22
21
20
19
18
17
16
15
VREF
LED +
(V
C
)
SS
6
SS
OUT
EXPOSED
PAD
(PIN 29)
R
R
7
T
T
DISABLE4
SHORTLED
NC
PWM
NC
8
R
R
R
9
10
11
12
13
14
SYNC
NC
OPENLED
NC
T
SET
I
FB
R
R
SET
R
C
C
CTRL
V
C
C
C
f
3599 F13
Figure 13ꢀ Recommended Component Placement
3599fd
ꢀꢆ
LT3599
Typical applicaTions
12W LED Driver
1MHz Boost, 80mA per String, 10 LEDs per String
L1
D1
PV
IN
10µH
8V TO 24V
C2
C1
3.3µF
25V
4.7µF
50V
s2
V
IN
3.1V TO 5.5V
V
IN
V
SW
V
OUT
IN
V
C3
1µF
6.3V
IN
V
R5
100k
O_SW
R10
1M
R4
100k
R1
200k
SHORTLED
OPENLED
FB
SHDN/UVLO
PWM
R11
31.6k
PWM
R2
31.6k
SYNC
LT3599
CTRL
RT
R3
33.2k
V
R6
53.6k
REF
R7
53.6k
T
SET
LED1
LED2
LED3
LED4
R8
80.6k
DISABLE4
80mA PER STRING
I
V
GND
SS
SET
C
C4
47nF
R9
16.5k
R
C
100pF
C1: MURATA GRM21BR71E335K
C2: MURATA GRM31CR71H475K
D1: DIODES INC. DFLS240
10k
C
C
2.2nF
3599 TA02a
L1: VISHAY IHLP2020BZER100M01
PWM Dimming Range 1000:1
(10ms Period)
Efficiency
100
95
90
85
80
75
70
65
60
PV = 24V
IN
PWM
5V/DIV
PV = 12V
IN
I
LED
TOTAL
200mA/DIV
3599 TA02c
10µs/DIV
40
120 160 200 240 280 320
TOTAL LED CURRENT (mA)
3599 TA02b
80
3599fd
ꢀꢇ
LT3599
Typical applicaTions
12W LED Driver
400kHz Boost, Two LED Strings, 200mA per String, 8 LEDs per String
L1
22µH
D1
PV
IN
C2
9V TO 16V
C1
3.3µF
25V
4.7µF
50V
s3
V
IN
3.1V TO 5.5V
V
IN
V
SW
V
OUT
IN
V
C3
IN
R5
100k
V
O_SW
1µF
R4
R10
1M
6.3V
R3
464k
R1
SHORTLED
OPENLED
SHDN/UVLO
PWM
SYNC
100k
200k
8 LEDs/
STRING
FB
R11
39.2k
PWM
R2
64.9k
CTRL
LT3599
CTRL
RT
V
R12
64.9k
R6
154k
REF
R7
LED1
LED2
LED3
LED4
53.6k
T
SET
R8
200mA PER STRING
100pF
DISABLE4
80.6k
I
V
GND
SS
SET
C
C4
47nF
R9
13.3k
R
C
3.01k
C
C1: MURATA GRM21BR71E335K
C2: MURATA GRM31CR71H475K
D1: DIODES INC. DFLS240
C
10nF
3599 TA03a
L1: VISHAY IHLP2525CZER220M11
3599fd
ꢀꢈ
LT3599
Typical applicaTions
7W LED Driver
SEPIC (Survives Output Sꢁort to Ground)
300kHz, Tꢁree Strings, 100mA per String, 6 LEDs per String
C7
4.7µF
25V
10Ω
L1
22µH
PV
IN
D1
8V TO 16V
C2
4.7µF
50V
s2
C1
3.3µF
25V
C6
1µF
25V
L2
22µH
V
IN
3.1V TO 5.5V
V
IN
V
SW
V
OUT
IN
C3
V
IN
V
R5
O_SW
1µF
6.3V
100k
R10
1M
R4
6 LEDs/
STRING
R1
200k
SHORTLED
OPENLED
SHDN/UVLO
100k
FB
R11
49.9k
PWM
PWM
SYNC
R2
31.6k
LT3599
CTRL
RT
V
R3
33.2k
LED1
LED2
LED3
LED4
R6
210k
REF
R7
DISABLE4
53.6k
100mA PER STRING
T
I
SET
R8
V
GND
80.6k
SS
SET
C
C4
47nF
R9
13.3k
R
10k
C
C
100pF
C1: MURATA GRM21BR71E335K
C2: MURATA GRM31CR71H475K
D1: DIODES INC. B360A
C
2.2nF
3599 TA04a
L1, L2: VISHAY IHLP2525CZER220M11
3599fd
ꢁ0
LT3599
Typical applicaTions
8W LED Driver
2MHz Boost, Tꢁree Strings, 100mA per String, 7 LEDs per String
L1
4.7µH
PV
IN
D1
8V TO 16V
C2
C1
3.3µF
25V
4.7µF
50V
s2
V
IN
3.1V TO 5.5V
V
IN
V
SW
V
OUT
IN
V
C3
IN
R5
100k
V
O_SW
1µF
R10
1M
R4
100k
6.3V
R1
200k
SHORTLED
OPENLED
SHDN/UVLO
PWM
7 LEDs/
STRING
FB
R11
43.2k
PWM
R2
31.6k
SYNC
LT3599
CTRL
RT
REF
R3
33.2k
LED1
LED2
LED3
LED4
V
R6
21.5k
R7
53.6k
DISABLE4
100mA PER STRING
T
SET
R8
80.6k
I
V
GND
SS
SET
C
C1: MURATA GRM21BR71E335K
C2: MURATA GRM31CR71H475K
D1: DIODES INC. DFLS240
C4
47nF
R9
13.3k
R
C
100pF
10k
C
3599 TA05a
L1: SUMIDA CDRH4D22HPNP-4R7N
C
2.2nF
3599fd
ꢁꢀ
LT3599
Typical applicaTions
2ꢀ1 MHz Boost, Four Strings, 80mA per String, 7 LEDs per String
L1
4.7µH
PV
IN
D1
9V TO 16V
C2
C1
3.3µF
25V
4.7µF
50V
s2
V
IN
3.1V TO 5.5V
V
IN
V
SW
V
OUT
IN
V
C3
IN
R5
100k
V
O_SW
1µF
R10
1M
R4
100k
6.3V
R1
200k
SHORTLED
OPENLED
SHDN/UVLO
PWM
FB
7 LEDs/
STRING
R11
43.2k
PWM
R2
32.4k
SYNC
LT3599
CTRL
RT
REF
R3
32.4k
LED1
LED2
LED3
LED4
V
R6
20k
R7
53.6k
80mA PER STRING
T
SET
R8
80.6k
V
C
DISABLE4
I
100pF
R
C
SS
GND
SET
10k
C4
47nF
R9
16.5k
C
C
C1: MURATA GRM21BR71E335K
C2: MURATA GRM31CR71H475K
D1: DIODES INC. DFLS240
2.2nF
3599 TA06a
L1: SUMIDA CDRH4D22HPNP-4R7N
PWM Dimming 3000:1
(10ms Period)
PWM
5V/DIV
I
LED
TOTAL
200mA/DIV
3599 TA07
10µs/DIV
3599fd
ꢁꢁ
LT3599
package DescripTion
FE Package
28-Lead Plastic TSSOP (4ꢀ4mm)
(Reference LTC DWG # 05-08-1663)
Exposed Pad Variation EB
9.60 – 9.80*
(.378 – .386)
4.75
(.187)
4.75
(.187)
28 2726 25 24 23 22 21 20 19 18 1716 15
6.60 ±0.10
2.74
(.108)
EXPOSED
PAD HEAT SINK
ON BOTTOM OF
PACKAGE
4.50 ±0.10
SEE NOTE 4
6.40
2.74
(.252)
(.108)
BSC
0.45 ±0.05
1.05 ±0.10
0.65 BSC
RECOMMENDED SOLDER PAD LAYOUT
5
7
1
2
3
4
6
8
9 10 12 13 14
11
1.20
(.047)
MAX
4.30 – 4.50*
(.169 – .177)
0.25
REF
0° – 8°
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
FE28 (EB) TSSOP 0204
(.0077 – .0118)
TYP
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS 4. RECOMMENDED MINIMUM PCB METAL SIZE
2. DIMENSIONS ARE IN
FOR EXPOSED PAD ATTACHMENT
MILLIMETERS
(INCHES)
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.150mm (.006") PER SIDE
3. DRAWING NOT TO SCALE
3599fd
ꢁꢂ
LT3599
package DescripTion
UH Package
32-Lead Plastic QFN (.mm × .mm)
(Reference LTC DWG # 05-08-1693 Rev D)
0.70 p0.05
5.50 p0.05
4.10 p0.05
3.45 p 0.05
3.50 REF
(4 SIDES)
3.45 p 0.05
PACKAGE OUTLINE
0.25 p 0.05
0.50 BSC
RECOMMENDED SOLDER PAD LAYOUT
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
BOTTOM VIEW—EXPOSED PAD
PIN 1 NOTCH R = 0.30 TYP
OR 0.35 s 45° CHAMFER
R = 0.05
TYP
0.00 – 0.05
R = 0.115
TYP
0.75 p 0.05
5.00 p 0.10
(4 SIDES)
31 32
0.40 p 0.10
PIN 1
TOP MARK
(NOTE 6)
1
2
3.45 p 0.10
3.50 REF
(4-SIDES)
3.45 p 0.10
(UH32) QFN 0406 REV D
0.200 REF
0.25 p 0.05
0.50 BSC
NOTE:
1. DRAWING PROPOSED TO BE A JEDEC PACKAGE OUTLINE
M0-220 VARIATION WHHD-(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 0.20mm 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
3599fd
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.
ꢁꢃ
LT3599
revision hisTory (Revision ꢁistory begins at Rev D)
REV
DATE
DESCRIPTION
PAGE NUMBER
D
01/10 Updated Typical Applications
1, 18, 19, 20, 21, 22
Added H-Grade to Abs Max Ratings and Order Information
Updated Typical Performance Characteristics
Revised Pin Functions
2
5, 6
7
Updated Table 6 and Deleted Text in Programming Switching Frequency Section
Added to Related Parts Table
14
26
3599fd
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.
ꢁꢄ
LT3599
relaTeD parTs
PART NUMBER DESCRIPTION
COMMENTS
LT3463/
LT3463A
Dual Output, Boost/Inverter, 250mA I , Constant
SW
V : 2.3V to 15V, V
= 40V, I = 40µA, I < 1µA, 3mm × 3mm
Q SD
IN
OUT(MAX)
OUT(MAX)
Off-Time, High Efficiency Step-Up DC/DC Converter with
DFN-10 Package
Integrated Schottkys
LT3466/
LT3466-1
Dual Constant Current, 2MHz, High Efficiency White LED
Boost Regulator with Integrated Schottky Diode
V : 2.7V to 24V, V
= 40V, I = 5µA, I < 16µA, 3mm × 3mm
Q SD
IN
DFN-10 Package
LT3474
LT3475
LT3476
LT3477
36V, 1A (I ), 2MHz, Step-Down LED Driver
V : 4V to 36V, V
SD
= 13.5V, True Color PWM Dimming = 400:1,
LED
IN
OUT(MAX)
OUT(MAX)
I
< 1µA, TSSOP-16E Package
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
SD
I
< 1µA, TSSOP-20E Package
Quad Output 1.5A, 2MHz High Current LED Driver with
1000:1 Dimming
V : 2.8V to 16V, V
= 36V, True Color PWM Dimming = 1000:1,
IN
SD
OUT(MAX)
OUT(MAX)
I
< 3µA, 5mm × 7mm QFN-10 Package
3A, 42V, 3MHz Boost, Buck-Boost, Buck LED Driver
V : 2.5V to 25V, V
= 40V, Dimming = Analog/PWM,
IN
SD
I
< 1µA, QFN and TSSOP-20E Packages
LT3478/
LT3478-1
High Current LED Driver
V : 2.8V to 36V, V
SD
= 42V, True Color PWM Dimming = 3000:1,
IN
OUT(MAX)
I
< 10µA, TSSOP-16E Package
LT3486
LT3496
LT3497
LT3498
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
45V, 2.1MHz 3-Channel (I
LED Driver
= 1A) Full Featured
V : 3V to 30V (40V
), V
= 45V, True Color PWM Dimming =
LED
IN
MAX
OUT(MAX)
3000:1, I < 1µA, 4mm × 5mm QFN-28 Package
SD
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
2.3MHz, 20mA LED Driver and OLED Driver with
Integrated Schottkys
V : 2.5V to 12V, V
= 32V, I = 1.65mA, I < 9µA, 2mm × 3mm
IN
Q
SD
DFN-12 Package
LT3518/
LT3517
2.3A/1.3A 45V, 2.5MHz Full Featured LED Driver with True V : 3V to 30V (40V
), V = 42V, True Color PWM Dimming =
OUT(MAX)
IN
MAX
Color PWM Dimming
3000:1, I < 5µA, 4mm × 4mm QFN-16 Package
SD
LT3590
48V Buck Mode LED Driver
V : 4.5V to 55V, V
= 5V, I = 700µA, I < 15µA,
OUT(MAX) Q SD
IN
2mm × 2mm DFN-6 and SC70 Packages
LT3591
Constant Current, 1MHz, High Efficiency White LED Boost
Regulator with Integrated Schottky Diode and 80:1 True
Color PWM Dimming
V : 2.5V to 12V, V
= 40V, I = 4mA, I < 9µA, 2mm × 3mm
Q SD
IN
OUT(MAX)
DFN-8 Package
LT3595
LT3598
LT3754
LT3760
45V, 2.5MHz 16-Channel Full Featured LED Driver
44V, 1.5A, 2.5MHz Boost 6-Channel LED Driver
16-Channel × 50mA LED Driver
V : 4.5V to 45V, V
SD
= 45V, True Color PWM Dimming = 5000:1,
IN
OUT(MAX)
I
< 1µA, 5mm × 9mm QFN-56 Package
V : 3V to 30V, V
SD
= 44V, True Color PWM Dimming = 3000:1,
IN
OUT(MAX)
I
< 1µA, 4mm × 4mm QFN-24 Package
V : 6V to 40V, V
SD
= 60V, 3,000:1 True Color PWM Dimming,
IN
OUT(MAX)
I
< 2µA, 5mm × 5mm QFN-32 Package
V : 6V to 40V, V
SD
= 60V, 3,000:1 True Color PWM Dimming,
OUT(MAX)
8-Channel × 100mA LED Driver
IN
I
< 2µA, TSSOP-28E Package
3599fd
LT 0110 REV D • PRINTED IN USA
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
ꢁꢅ
●
●
LINEAR TECHNOLOGY CORPORATION 2009
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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