Dear Mehmet,

Could generally gather your setup details. My concerns in such a setup would be :

1. The LM2917 can aim at a conversion linearity of around +/- 1% ( though typical is around +/- 0.3% ). Is this OK for you ?

2. What is the capacitor resistor that you have used for the integration ( the R1+C2 combo in the National data sheet ) ? This has a significant influence on the output update rates and if you try to make it fast then your ripple will go high.

3. HAve you been able to work out the overall loop gain of the system and the step response of the driven load ? That should give you an idea of the required correction update frequency. This will also tell you the limits on accelaration and decelartion parameters to remain in synch with the command.

4. Mixing up digital and analog circuits - and particularly stuff like LM2917 in the feedback loop would'nt be easy. Cant you go digital all the way ?