3-Channel Constant Current LED Driver

with Programmable PWM Control

A6281

3

Allegro MicroSystems, LLC

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

OUT2

OUT1

OUT0

Regulator

800 kHz Clock

To PWM Counters

To logic

To PWM Counters

Current

Regulator 0

Current

Regulator 1

Current

Regulator 2

Latched Registers

REXT

LGND

PGND

OEO

OEI

VIN

VREG

LI

LO

Shift Register

SDI

CI

SDO

CO

100 ns

One-Shot

Terminal List Table

Number

Name

Description

1

REXT

An external resistor at this terminal establishes maximum output current

2

VREG

Regulator decoupling

3

LGND

Logic ground

4

VIN

5

CI

Serial clock input; PWM clock if external clock is selected

6

OEI

Output enable input; when low (active), the output drivers are enabled; when high (inactive), all

output drivers are turned off (blanked)

7

LI

Latch input terminal; serial data is latched with high-level input

8

SDI

Serial data input to shift register

9

OUT2

Sinking output terminal

10

PGND

Power ground

11

OUT1

Sinking output terminal

12

OUT0

Sinking output terminal

13

SDO

Buffered serial data output after shift register

14

LO

Buffered latch output

15

OEO

Buffered output enable output

16

CO

Buffered clock output

–

PAD

Exposed thermal pad, not internally connected; connect externally to LGND and PGND.

Pin-out Drawings

Functional Block Diagram

12

11

10

9

1

2

3

4

OUT0

OUT1

PGND

OUT2

REXT

VREG

LGND

VIN

PAD