MAX6979 Ver la hoja de datos (PDF) - Maxim Integrated

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Fabricante

MAX6979

16-Port, 5.5V Constant-Current LED Driver with LED Fault Detection and Watchdog

Maxim Integrated 

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

LED Fault Detection and Watchdog

PIN

1

2

3

4

5–20

21

22

23

24

Pin Description

NAME

GND

DIN

CLK

LE

OUT0–

OUT15

OE

DOUT

SET

V+

Ground

FUNCTION

Serial-Data Input. Data is loaded into the internal 16-bit shift register on CLK’s rising edge.

Serial-Clock Input. Data is loaded into the internal 16-bit shift register on CLK’s rising edge.

Load-Enable Input. Data is loaded transparently from the internal shift register(s) to the output latch(es)

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

LED Driver Outputs. OUT0 to OUT15 are open-drain, constant-current-sinking outputs rated to 5.5V.

Output Enable Input. High forces outputs OUT0 to OUT15 high impedance without altering the contents of

the output latches. Low enables outputs OUT0 to OUT15 to follow the state of the output latches.

Serial-Data Output. Data is clocked out of the 16-bit internal shift register to DOUT on CLK’s rising edge.

LED Current Setting. Connect SET to GND through a resistor (RSET) to set the maximum LED current.

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

CLK

MAX6979

DIN

D0 SERIAL-TO-PARALLEL SHIFT REGISTER D15

LE

D0

LATCHES

D15

POWER-ON

RESET

WATCH-

OE

DOG

V+

D0

CONSTANT-CURRENT SINKS

D15

FAULT DETECTION

CURRENT

REFERENCE

OUT0

OUT2

OUT1

Figure 1. MAX6979 Block Diagram

OUT13

OUT15

OUT14

GND

DOUT

V+

RSET

GND

Detailed Description

The MAX6979 LED driver comprises a 4-wire serial

interface driving eight constant-current sinking open-

drain output ports. The outputs drive LEDs in either sta-

tic or multiplex applications (Figure 1). The constant-

current outputs are guaranteed for current accuracy

not only with chip-supply voltage variations (5V ±10%

and 3V to 5.5V), but also over a realistic range of driver

output voltage drop (0.5V to 2.5V). The drivers use cur-

rent-sensing feedback circuitry (not simple current mir-

rors) to ensure very small current variations over the full

allowed range of output voltage (see the Typical

Operating Characteristics).

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