I buy a AD9708 ,however its resolution is not enough for my system ，so I want to extend the resolution of DAC in software ,is there any way ? I read some articles of PWM ? sigma-delta ? thanks a lots for your answers
Not sure if I fully understand the question, but if you need a 10-bit DAC why did you buy an 8-bit DAC?... I do not mean to be cavalier about it, but if DAC resolution could be easily increased through software, why would ADI offer HS DACs with 8, 10, 12, 14, and 16-bit variants, each priced according to their resolution?
A good 14-bit alternative to the AD9708 is the AD9744. AD9740 and AD9742 are its 10-bit and 12-bit variants, with AD9740 is priced similarly to AD9708.
thank you so much .what I think is I already put a AD9708 in my system( E-board)，it used to work good for my system, however , I want to decrease the system noise to work better ,but I don't want to make a new board. so I want to know is there any way to improve DAC resolution in software. according to my knowledge , some way called sigma-delta modulation may help , but I don't how .
Sigma-delta is a specific converter architecture which sacrifices BW for improved noise spectral density across a narrow band. I am not sure on the processing requirements for such as setup. One would basically use noise-shaping to post process the data, assuming the carrier is at a low enough frequency. I am not sure on the best way to AD9708 implement this on an FPGA with a current-steering or a voltage DAC. But it can be theoretically done.
update: you may find the following application note interesting: