Datasheet

MAX6978
8-Port, 5.5V Constant-Current LED Driver with
LED Fault Detection and Watchdog
6 _______________________________________________________________________________________
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 LED Current Setting. Connect SET to GND through a resistor (R
SET
) to set the maximum LED current.
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
R
SET
MAX6978
FAULT DETECTION
WATCH
DOG
Figure 1. MAX6978 Block Diagram
*TSSOP package only.