LM3431_08 Datasheet, PDF (3/24 Pages) National Semiconductor (TI) – 3-Channel Constant Current LED Driver with Integrated Boost Controller

Pin Descriptions
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
EP
Pin Name
VIN
PGND
VCC
LG
CS
ILIM
MODE/F
FF
RT
REF
REFIN
COMP
SGND
AFB
SS/SH
DLY
CFB
SC
LEDOFF
SNS3
NDRV3
SNS2
NDRV2
SNS1
NDRV1
THM
DIM
EN
Description
Power supply input.
Power ground pin. Connect to ground.
Internal reference voltage output. Bypass to PGND with a minimum 4.7 µF capacitor.
Boost controller gate drive output. Connect to the NFET gate.
Boost controller current sense pin. Connect to the top side of the boost current sense resistor.
Boost controller current limit adjust pin. Connect a resistor from this pin to the Boost current sense resistor
to set the current limit threshold.
Dimming mode selection pin. Pull high for digital PWM control. Or connect to a capacitor to GND to set
the internal dimming frequency.
Feedforward pin. Connect to a resistor to ground to control the output voltage over/undershoot during
PWM dimming.
Frequency adjust pin. Connect a resistor from this pin to ground to set the operating frequency of the
boost controller.
Reference voltage. Use this pin to provide the REFIN voltage.
This pin sets the LED current feedback voltage. Connect to a resistor divider from the REF pin.
Output of the error amplifier. Connect to the compensation network.
Signal ground pin. Connect to ground.
Anode feedback pin. The boost controller voltage feedback during LED off time. Connect this pin to a
resistor divider from the output voltage.
Soft-start and sample-hold pin. Connect a capacitor from this pin to ground to set the soft-start time.
Fault delay pin. Connect a capacitor from this pin to ground to set the delay time for shutdown.
Cathode feedback pin. The boost controller voltage feedback. Connect through a diode to the bottom
cathode of each LED string.
LED short circuit detection pin. Connect through a diode to the bottom cathode of each string.
A dual function pin. The LEDOFF signal controls external drivers during PWM dimming. Or connect to
ground to enable automatic fault restart.
Current feedback for channel 3. Connect to the top of the channel 3 current sense resistor.
Base drive for the channel 3 current regulator. Connect to the NPN base or NFET gate.
Current feedback for channel 2.
Base drive for the channel 2 current regulator.
Current feedback for channel 1.
Base drive for the channel 1 current regulator.
LED thermal monitor input pin. When pulled below 1.2V, device enters standby mode.
PWM dimming input pin. Accepts a digital PWM or analog voltage level input to control LED current duty
cycle.
Enable pin. Connect to VIN through a resistor divider to set an external UVLO threshold. Pull low to
shutdown.
Exposed pad. Connect to SGND.
3
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