Using AD7840 14 bit DAC as 8 bit DAC

[okbro]

hi,

I have a 14 bit DAC AD7840 which I want to use as 8 bit DAC for use with Arduino. Can it be done?

Thanks

 

[Ian Rogers]

Yep... Stick it in Mode1 and drop the LSByte

 

[Pommie]

Yup, read the 14 bits and shift it right 6 times. But, why?

Mike.

 

[Les Jones]

Mike, I think you are thinking of an ADC when you say READ 14 bits. As it is a DAC if the OP only wants to use 8 bits I think using the top 8 bits would best. If he was using the parallel load option then he could just connect the top 8 bits and ground the lower 6 bits. If he was loading it serially he would probably have to send all 14 bits and just make the lower 6 bits zeroes.

Les.

 

[Pommie]

Yup, read DAC as ADC. Do as Les says.

Mike.

 

[Ian Rogers]

Mike, I think you are thinking of an ADC when you say READ 14 bits. As it is a DAC if the OP only wants to use 8 bits I think using the top 8 bits would best. If he was using the parallel load option then he could just connect the top 8 bits and ground the lower 6 bits. If he was loading it serially he would probably have to send all 14 bits and just make the lower 6 bits zeroes.

Les.

There are four modes.... One is MSB justified into a 16 bit.... Just lose the bottom byte..

 

[Les Jones]

Hi Ian, I only skimmed through the data sheet to see how the DAC communicated with the micro. (I was expecting it to be I2C.) I can't understand why the OP is using such an expensive IC when only 8 bits is required. (I looked up the price as I thought it looked a useful device. It costs about £23 so I lost interest.) I think if I wanted an 8 bit DAC I would just use a R/2R network.

Les.