MAX6974 查看數據表（PDF） - Maxim Integrated

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MAX6974

24-Output PWM LED Drivers for Message Boards

Maxim Integrated 

24-Output PWM LED Drivers

for Message Boards

The global-intensity data is received in an intermediate

register and is applied to the outputs at subframe 0 and

PWM clock 0.

The MAX6974/MAX6975 have one byte of configuration

data with 5 active bit settings as shown in Table 6. One

byte of data containing configuration bit settings is sent

three times. Data is updated immediately into the CAL-

DAC latches. See Table 10. The loaded configuration

settings take effect immediately.

Serial Interface

The MAX6974/MAX6975 feature a fully synchronous

and fully buffered serial interface that allows cascading

of multiple devices. The serial interface consists of

inputs (CLKI, DIN, and LOADI) and outputs (CLKO,

DOUT, and LOADO). The MAX6974/MAX6975 can

pass different data to each cascaded device without

any additional inputs to identify the position of the

devices in the cascaded chain.

Table 6. Load Configuration Bit Definitions

CONFIGURATION BIT

MSB

D7

D6

D5

ACRONYM

—

—

—

FUNCTION

0

0

0

Not used

Not used

Not used

DESCRIPTION

Enables the reduced global-intensity setting in the MAX6975 when set to

D4

GLB4

Global quarter

1. When set, the MAX6975 uses eight (or four, if multiplexing) PWM

subframes. GLB4 is set to 0 as power-on default. Setting bit D4 has no

effect in the MAX6974.

D3

D2

D1

LSB

D0

PWM-ON

CRST

WDOG

MUX

Enable

individual

PWMs

Turns all individual PWM outputs on when set to 1. Power-on default is

PWM-ON set to 0 to disable all current output drivers. PWM-ON can be

used to turn all LEDs on or off without affecting the global-intensity or

individual PWM settings.

Reset frame

and PWM

counters

Setting CRST to 1 synchronously resets internal counters to 0. This action

sets the MAX6974/MAX6975 to subframe 0 of the global-intensity

subframe counter and clock 0 of all individual PWM counters. The CRST

bit is a nonlatching control function that resets to 0 after the counters are

set to 0.

Watchdog

enable

Multiplex

enable

Setting WDOG to 1 enables the watchdog timer operation. Power-on

default is 0.

Setting MUX to 1 turns multiplex mode on. Power-on default is 0.

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