Datasheet

ManualsBrandsMICROCHIP TECHNOLOGY ManualsData collecting ICsData acquisition IC - DA converter (DAC) MSOP 10

MCP4728

5 . 6 . 1 F A S T W R I T E C O M M A N D

(C2=0, C1=0, C0=X, X = DON’T

CARE)

The Fast Write command is used to update the input

DAC registers from channels A to D sequentially. The

EEPROM data is not affected by this command. This

command is called “Fast Write” because it updates the

input registers with only limited data bits. Only the

Power-Down mode selection bits (PD1 and PD0) and

12 bits of DAC input data are writable.

The input register is updated at the acknowledge pulse

of each channel’s last data byte. Figure 5-7 shows an

example of the Fast Write command.

Updating Analog Outputs:

a. When the LDAC pin is “High” before the last byte

of the channel D, all analog outputs are updated

simultaneously by bringing down the LDAC pin

to “Low” any time.

b. If the command starts with the LDAC

pin “Low”,

the channel’s analog output is updated at the

falling edge of the acknowledge clock pulse of

the channel’s last byte.

c. Send the General Call Software Update

command: This command updates all channels

simultaneously.

5.6.2 MULTI-WRITE COMMAND: WRITE

DAC INPUT REGISTERS

(C2=0, C1=1, C0=0; W1=0, W0=0)

This command is used to write DAC input register, one

at a time. The EEPROM data is not affected by this

command.

The DAC selection bits (DAC1, DAC0) select the DAC

channel to write. Only a selected channel is affected.

Repeated bytes are used to write more multiple DAC

registers.

The D11 - D0 bits in the third and fourth bytes are the

DAC input data of the selected DAC channel.

Bytes 2 - 4 can be repeated for the other channels.

Figure 5-8 shows an example of the Multi-Write

command.

Updating Analog Outputs:

The analog outputs can be updated by one of the

following events after the falling edge of the

acknowledge clock pulse of the 4th byte.

a. When the LDAC

pin or UDAC bit is “Low”.

b. If UDAC bit is “High”, bringing down the LDAC

pin to “Low” any time.

c. By sending the General Call Software Update

command.

Note: The U

DAC bit is not used in this

command.

Note: The UDAC bit can be used effectively to

upload the input register to the output

channel only, while the LDAC

pin and

General Call Software Update command

affect all channels.