8-Port, 5.5V Constant-Current LED Driver with

LED Fault Detection and Watchdog

6

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Pin Description

PIN

NAME

FUNCTION

1

GND

Ground

2

DIN

Serial-Data Input. Data is loaded into the internal 8-bit shift register on CLK’s rising edge.

3

CLK

Serial-Clock Input. Data is loaded into the internal 8-bit shift register on CLK’s rising edge.

4LE

Load-Enable Input. Data is loaded transparently from the internal shift register to the output latch while

LE is high. Data is latched into the output latch on LE's falling edge, and retained while LE is low.

5–12

OUT0–OUT7

LED Driver Outputs. OUT0–OUT7 are open-drain, constant-current sinking outputs rated to 5.5V.

13

OE

Output-Enable Input. High forces outputs OUT0–OUT7 to high impedance, without altering the contents

of the output latches. Low enables outputs OUT0–OUT7 to follow the state of the output latches.

14

DOUT

Serial-Data Output. Data is clocked out of the 8-bit internal shift-register to DOUT on CLK’s rising edge.

15

SET

16

V+

Positive Supply Voltage. Bypass V+ to GND with a 0.1µF ceramic capacitor.

PAD

Exposed Pad*

Exposed pad on package underside. Connect to GND.

SERIAL-TO-PARALLEL SHIFT REGISTER

LATCHES

OUT0

OUT1

OUT2

DOUT

DIN

CLK

OUT7

CONSTANT-CURRENT SINKS

OUT5

OUT6

POWER-ON

RESET

V+

CURRENT

REFERENCE

V+

OE

GND

GND

LE

D0

D7

D0

D7

D0

D7

MAX6978

FAULT DETECTION

WATCH

DOG

Figure 1. MAX6978 Block Diagram

*TSSOP package only.