Other Parts Discussed in Thread: TDC1000, TDC7200
We are designing an air flow meter using 400kHz sensors with the TDC1000 and TDC7200 devices. We have a 4-pole 400kHz narrow bandpass filter between TDC1000 PGAOUT and COMPIN pins which is working well but finding that if the PGA gain is set above 15dB (5) the signal at PGAOUT disappears. After some testing the issue seems to be related to loading on the PGAOUT pin. Currently we have a 10k resistive load to analogue ground and a unity gain buffer amp between the PGAOUT pin and the bandpass filter input but still cannot get above 15dB gain.
The design will require dynamic adjustment of gain based on received signal strength and use of the full PGA gain range is required.
Can someone please advise the specific loading requirements of the PGAOUT pin so we know what we have to deal with?
