LM3431_14 Datasheet, PDF (3/36 Pages) Texas Instruments – 3-Channel Constant Current LED Driver with Integrated Boost Controller

LM3431
www.ti.com
SNVS547F – NOVEMBER 2007 – REVISED MARCH 2009
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
CONNECTION DIAGRAM
VIN 1
PGND 2
VCC 3
LG 4
CS 5
ILIM 6
MODE/F 7
FF 8
RT 9
REF 10
REFIN 11
COMP 12
SGND 13
AFB 14
Top View
28 EN
27 DIM
26 THM
25 NDRV1
24 SNS1
23 NDRV2
22 SNS2
21 NDRV3
20 SNS3
19 LEDOFF
18 SC
17 CFB
16 DLY
15 SS/SH
Exposed Pad
Connect to SGND
Figure 1. 28 Lead Plastic Exposed Pad TSSOP
See Package Number PWP0028A
Pin No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Pin Name
VIN
PGND
VCC
LG
CS
ILIM
MODE/F
FF
RT
REF
REFIN
COMP
SGND
AFB
SS/SH
DLY
CFB
SC
LEDOFF
SNS3
PIN DESCRIPTIONS
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.
Copyright © 2007–2009, Texas Instruments Incorporated
Product Folder Links: LM3431
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