LT3476 Datasheet, PDF (1/12 Pages) Linear Technology – High Current Quad Output LED Driver

FEATURES
■ _{True Color PWM}^TM _{Dimming Delivers Up to 5000:1}
Dimming Ratio (In Boost Configuration)
■ _{LED Current Regulation with High-Side Sense}
■ _{VADJ Pin Accurately Sets LED Current Sense}
Threshold Over Range 10mV to 120mV
■ _{Four Independent Driver Channels with 1.5A, 36V}
Internal NPN Switches
■ _{Frequency Adjust Pin: 200kHz to 2MHz}
■ _{High Efficiency Conversion = Up to 96%}
■ _{Open LED Protection}
■ _{Low Quiescent Current}
22mA in Active Mode
<10μA in Shutdown Mode
■ _{Wide VIN Range: 2.8V to 16V}
■ _{Thermally Enhanced, 38-Lead, 5mm × 7mm}
QFN Package
U
APPLICATIO S
■ _{RGGB Lighting}
■ _{Automotive and Avionic Lighting}
■ _{TFT LCD Backlighting}
■ _{Constant-Current Sources}
LT3476
High Current
Quad Output LED Driver
DESCRIPTIO
The LT^®3476 is a quad output DC/DC converter designed
to operate as a constant-current source for driving high
current LEDs. A fixed frequency, current mode architecture
results in stable operation over a wide range of supply and
output voltages. A frequency adjust pin allows the user to
program switching frequency between 200kHz and 2MHz
to optimize efficiency and external component size.
The LT3476 senses output current at the high side of
the LED. High side current sensing is the most flexible
scheme for driving LEDs, allowing buck, boost or buck-
boost configurations. Each current monitor threshold is
trimmed to within 2.5% at the full scale of 105mV. With
an external sense resistor, the user programs the output
current range of each channel. Each of the four regulators
is independently operated by that channel’s PWM signal.
This PWM feature allows precise adjustment of the color
mixing or dimming ratio of the LED source. Dimming
ratios up to 1000:1 can be achieved.
, 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.
TYPICAL APPLICATIO
100W Quad 1A × 8 LED Driver
PV_IN
33V
CAP1
CAP2
CAP3
100mΩ
100mΩ
100mΩ
LED1
LED2
LED3
CAP4
100mΩ
LED4
UP TO
8 LEDS
1A
0.22μF
1A
0.22μF
1A
0.22μF
1A
0.22μF
2.2μF
×4
10μH
10μH
10μH
10μH
1000:1 PWM Dimming at 100Hz
PWM
5V/DIV
I_LED
500mA/DIV
5μs/DIV
3476 TA02
V_IN
2.8V TO 16V
PWM1-4
SHDN
2.2μF
SW1
CAP1-4
LED1-4
V_IN
PWM1-4
SHDN
SW2
SW3
LT3476
GND
SW4
REF
VADJ1-4
VC1-4
R_T
3476 TA01
1.05V
4.99k
100k
21k
1nF
3476fa
1