Part Number:ADS5277
Hello there,
we have designed a waveform capture circuit using ADS5277 and an OP-Amp + single end to differential convertor with FPGA connecting the output of ADS5277. However the reading is not stable (incorrect neither) even though the readings using the ADS5277's test mode are correct. To simplify the problem, we feed DC into the system (our DC is about -0.875V when entering the single to differential convertor), but the reading is around 0x275 and the variation can go up to 0x390. after further reviewing our schematic, we did find several issues but problem exists after we fixing the issue.
And one more sympton:
Vcm reading =0.25V instead of 1.45V as specified in the datasheet.
Please see the enclosed file for our schematic and changes we made.
thanks for your help!
Hong(Please visit the site to view this file)