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ADS8557: operating mode without HVDD/HVSS voltages

Marina Iriarte40
Prodigy 190 points
Part Number: ADS8557

Hello,

Question related to ADS8557IPM: If we have no HVDD/HVSS voltages (due to a failure in a DC/DC converter for example). Would the digital part still work? I mean, if we have HVDD=HVSS=0V; and AVDD=BVDD=5V, would BUSY signal go up and down (we assume that the converted values woud have nos sense)? Or it would stay always down? (we have CR bit 21='0').

In this situation, what would be the expected read value? All '0's or full-scale value?

Thanks,

  • 0
    TI__Guru**** 176421 points

    Hi Marina!

    Great question on the ADS8557!  To be honest, I don't know how the 'converter side' will work without the HV analog supply connected.  For sure the conversion results will be wrong.  Let me hook up an evaluation module in the lab and I'll let you know what I see.

  • +1 in reply to Tom Hendrick
    TI__Guru**** 176421 points

    So, without HVDD and HVSS there is still activity on the control lines (i.e. BUSY goes active with a CONVST input), but the conversion values are wrong.  The results are noisy and distorted - neither all 0's nor full-scale - just wrong, no sense as you expected..