We have a few questions about your AFE5848s. We recently found a single channel on one AFE with a higher DC offset than we would expect – when all of the other channels had an offset within +/-500 counts, this one’s offset was at ~1800 counts. The offset did not appear at the input to the AFE, nor were any components missing/damaged/poorly connected. (We were using the digital TGC with 3dB of attenuation, an LNA gain setting of 15dB and a PGA gain setting of 18dB).
The only spec I could find regarding the dc offset was the one from page 18, which only specifies a typical value of +/-800 LSBs. This was specified with a TGC near full scale, an LNA gain of 18dB and a PGA gain of 24dB. Based off of this, we would expect that if we increased our gains to match the gains from the spec, the DC offset we saw on this channel would be even larger.
Is this spec tested on each AFE, tested on a few from every batch, or assumed guaranteed by design? Do you have a maximum value for this spec instead of just a typical value? We would like channel-to-channel uniformity while maximizing the dynamic range of the result, so we’ll be writing a test to catch “bad” channels – but a maximum value or some knowledge of how many outliers we should anticipate would help us set reasonable limits for our test.
Thanks,
Michaela
