I was testing the PSIEVM PA045B output with the Precision Signal Injector tool, and I noticed that I was unable to change the offset. I verified with the user guide that the SE_VCM jumper JP4 was connected to VCM and the DIF_VCM jumper JP8 was connected to ground for single-ended mode. However, I was unable to change the offset in the tool unless I changed JP1 and JP3 to use filter instead of bypass. There are two questions I have because of this issue:
- Why am I unable to change the DC offset voltage for single-ended mode while using bypass? Why does using the filter mode allow a DC offset to be configured?
- When I read in the data using single-ended offset and filter mode, I get the below waveform on the F280039C ControlCARD (PSI tool is set up to have an amplitude of 2.1V, offset of 1.25V, and frequency of 2 kHz). However, I when I test the same PSIEVM in bypass mode the signal is clean, the only issue is that it clips below 0V. I also checked with the AG33522A wavegen at 2 kHz and the signal was clean. Is there a reason why using the filter mode results in a more noisy signal?
I have tested this offset issue on 2 PSIEVMs, so I don't believe it's an issue with just the EVM that I have.