MCP4021 datasheet(26/64 Pages) MICROCHIP

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MCP4021/2/3/4

DS21945E-page 26

3.6

Chip Select (CS)

The CS pin is the chip select input. Forcing the CS pin

to VIL enables the serial commands. These commands

can increment and decrement the wiper. Depending on

the command, the wiper may (or may not) be saved to

non-volatile memeory (EEPROM). Forcing the CS pin

to VIHH enables the high-voltage serial commands.

These commands can increment and decrement the

wiper and enable or disable the WiperLock technology.

The wiper is saved to non-volatile memory (EEPROM).

The CS pin has an internal pull-up resistor. The resistor

will become “disabled” when the voltage on the CS pin

is below the VIH level. This means that when the CS pin

is “floating”, the CS pin will be pulled to the VIH level

(serial communication (the U/D pin) is ignored). And

when the CS pin is driven low (VIL), the resistance

becomes very large to reduce the device current

consumption when serial commands are occurring.

See Figure 2-4 for additional information.

3.7

Increment/Decrement (U/D)

The U/D pin input is used to increment or decrement

the wiper on the digital potentiometer. An increment

moves the wiper one step toward terminal A, while a

decrement moves the wiper one step toward

terminal B.

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