Hi all members
Recently i used an AD574 in my Fpga board,It works truly
I gave this schematic and pcb to my friend and he redesign his board with only one difference, 
using AD7862AN-3 (4 Channel ADC) instead of AD574.
He called me today for solving his problem,
bad treat of ADC
ADC-Out: 15DH 150H 152H 158H 15EH 150H .....160H
I doubt that this is for timing 
I check his code and did'nt see any problem
then i doubt to pcb , a gnd polygon , agnd and dgnd was apart and joint at one point
0.1uF multilayer decoupling caps near every supply pins
even i brought my power supply but the problem didn't solve!
Unfortunately my scope isn't calibrate these days and it's ground has 40-50 mv 
He used a 5k multi turn for ADC analog input, and 0.1uF,1uF multilayer and 10uF tantal for these inputs
Then i used software method(100 instances mean),but there are 
2 lsb fluctuate yet
Can you please say your valuable comment
Thanks beforehand
Mehdi