MAX6977 Ver la hoja de datos (PDF) - Maxim Integrated
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componentes Descripción
Fabricante
MAX6977 Datasheet PDF : 13 Pages
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8-Port, 5.5V Constant-Current LED Driver with
LED Fault Detection
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.
4
LE
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 (RSET) 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.
*TSSOP package only.
CLK
MAX6977
DIN
D0 SERIAL-TO-PARALLEL SHIFT REGISTER D7
LE
D0
LATCHES
D7
POWER-ON
RESET
DOUT
V+
OE
V+
D0
CONSTANT-CURRENT SINKS
D7
CURRENT
REFERENCE
FAULT DETECTION
RSET
GND
OUT0
OUT2
OUT1
OUT5
OUT7
OUT6
GND
Figure 1. MAX6977 Block Diagram
Detailed Description
The MAX6977 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 Typical Operating
Characteristics).
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