I met a problem totally different from my old experiences with under 10MHz ADC. I found that the output data of AD9265 will be different in different sampling rate, even the same input source (function generator with high impedance output).
For example, giving a 0.4V input, I got 0.4V in 10Msps, but 0.41 in 100Msps. Is this the feature of AD9265 or ?!
And I found the offset will increase in higher input voltage. ex 0.8V input, 0.8V in 10Msps. but 0.82V in 100MSps.
At first, I doubt the voltage reference may be affected when ADC operates faster in 100MSps. I applies a high-speed OPAMP to drive the voltage reference input. Furthermore, I applied the expensive low-ESR capacitor to stabilize the reference, but all of these are useless.
Had anyone experienced this?! Please give me some advice how to deal with this problem. Thank you.
I have tested another high speed ADC, AD9226ARSZ, 12-Bit 65MSps, to compare with AD9265, but i didn't find the gain error of AD9226 in different sampling rate. From the datasheet of AD9226ARSZ, it has max. 2% FSR gain error. We analyzed this spec. and find the output codes are almost the same under 30MHz and 1MHz sampling rate. Could you give us some points why these two parts, AD9265 & AD9226, are so different?! Are there any thing we could do to improve AD9265?!
Thank you for the reply.