MCP4728 datasheet(37/66 Pages) MICROCHIP

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DS22187C-page 37

MCP4728

5.6.5

WRITE COMMAND: SELECT VREF

BIT (C2=1, C1=0, C0=0)

When the device receives this command, it updates the

DAC voltage reference selection bit (VREF) of each

channel. The EEPROM data is not affected by this

command. The affected channel’s analog output is

updated after the acknowledge pulse of the last byte.

Figure 5-12 shows an example of the write command

for Select VREF bits.

5.6.6

WRITE COMMAND: SELECT

POWER-DOWN BITS (C2=1, C1=0,

C0=1)

When the device receives this command, it updates the

Power-Down selection bits (PD1, PD0) of each

channel. The EEPROM data is not affected by this

command. The affected channel is updated after the

acknowledge pulse of the last byte. Figure 5-13 shows

an example of the write command for the Select

Power-Down bits.

5.6.7

WRITE COMMAND: SELECT GAIN

BIT (C2=1, C1=1, C0=0)

When the device receives this command, it updates the

gain selection bits (GX) of each channel. The EEPROM

data is not affected by this command. The analog out-

put is updated after the acknowledge pulse of the last

byte. Figure 5-14 shows an example of the write com-

mand for select gain bits.

5.6.8

WRITE COMMAND: WRITE I2C

ADDRESS BITS (C2=0, C1=1, C0=1)

This command writes new I2C address bits (A2, A1,

A0) to the DAC input registers and EEPROM. When

the device receives this command, it overwrites the

current address bits with the new address bits.

This command is valid only when the LDAC pin makes

a transition from “High” to “Low” at the low time of the

last bit (8th clock) of the second byte, and stays “Low”

until the end of the 3rd byte. The update occurs after

“Stop” bit if the conditions are met. The LDAC pin is

used to select a device of interest to write. The highest

clock rate of this command is 400 kHz. Figure 5-11

shows the details of the address write command.

5.6.9

READ COMMAND

If the R/W bit is set to a logic “High” in the I2C serial

communications command, the device enters a

reading mode and reads out the input registers and

EEPROM. Figure 5-15 shows the details of the read

command.

Note 1: To write a new device address, the

current address of the device is also

required. If the current address is not

known, it can be read out by sending

General Call Read Address Bits com-

mand. See

5.4.4 “General call Read

Address Bits” for more details of reading

the I2C address bits.

Note 1: The device address bits are read by using

General

Call

Read

Address

Bits

command.

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