I am debugging AD9653 with Artix-7 FPGA and referenced the ADC_interface supplied by XAPP524.
The input of the signal is a sine wave which is fed by a signal generator. The outputs of each channel are monitored with a ILA in Vivado after the signals are deserialized in ADC_interface. The outputs of three channels, channel A, B, C, work well. But channel D doesn't show the right value range compared with other channels even though it received the sine wave. It seems that the highest one or two bits are always unavailable, like the picture below.
I tried to use test mode and it worked fine for all channels, in other words, the four channels could receive the same data that is generated by ADC.
The analogy inputs (refer to Fig.57 in AD9653 datasheet) are also checked, the parameters of the analog input are the same, and the amplitude and bias (from VCM, 0.9V) of input sine wave are the same as well.
Then what should I do to figure out the problem?
Thanks in advance.
Thank you for using the AD9653. It sounds like it is always Channel D that does not behave properly, across many power-ups, correct?
If you could, would you please try a Digital Reset to make sure that the ADC is initialized properly.SPI_Write (0x08, 0x03); Start Digital ResetSPI_Write (0x08, 0x00); Complete Digital Reset and return to normal operation
Maybe this will make no difference but at least we can be sure the ADC is in the right state.
What is your sample rate and what is the frequency of your test signal (sine wave)?
Thanks for your response.
I already had a digital reset for ADC. The sample rate is 100 MHz and the sine wave frequency is about 2 MHz.
We doubt there is something wrong with internal DC reference voltage circuit which was damaged by static electricity or improper soldering. Anyway I will try to think this problem from another angle.
You already mentioned that the amplitude of the sine wave is the same at all the inputs. Did you probe/measure the analog signal amplitude right at the ADC inputs?
What kind of circuit elements do you have between your signal source and the ADC inputs?
Do you see this on multiple parts/boards?