I have solved the power problem and here comes my design purpose, schematic and some questions:
I would like to control an optical modulator by a DAC. The DAC needs a precision of 0.1mV. The DAC will be connected with the modulator through a coaxial cable.
1.One end of modulator is connected with ground. In order to avoid ground loop, I think differential output(from LP filter after DAC) should be connected with the modulator, is that correct?
2. After DAC, there will be a low-pass filter, before connecting with the optical modulator. The output of the low pass filter will be differential pairs. Which kind of DAC should be used to connect with the differential output LP filter, a differential DAC or a voltage output DAC?
3. I have read in a tutorial (http://www.hit.bme.hu/~papay/edu/Acrobat/GndADCs.pdf) that the connection between DAC with data bus should be buffered to reduce digital return current. Is it also true for a microcontroller based application? If so, what kind of buffers should be used?
My current design: MicroController (No Buffer)---> Single end output voltage DAC--->single input differential output low pass filter---->Coaxial cable---->Optical modulator.
It would be really appreciated if you could give me any suggestions/advice on the questions/design.
BTW, I have watched 5 things you need to know about DACs. It is very useful.
Thank you very very much.