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C5515 SAR: NoHV bit?

Bill Finger
Genius 3735 points

 

SPRUFP1C talks about a NoHV bit that needs to be set to get measurements out of channels 0, 1, or 2.  However, I don't see that bit in any of the register descriptions.  Any hints how I can set it?

  

  • 0
    TI__Mastermind 23785 points

    Bill,

    This is an undocumented test feature to disable the high voltage protection circuit for the channels. The protection circuit is enabled by default for normal operation.

    Regards.

  • 0 in reply to Steve Tsang
    Prodigy 10 points

    If I want to use the channel 0-2, how can I do for it ?？？

  • 0 in reply to user1913996
    Intellectual 510 points
    I think that NoHV corresponds to bit 2 on SARPINCTRL register.
    Setting it to 1, I was able to read a voltage on GPAIN0 on channel 2.
    Voltage on GPAIN0 must NOT exceed VDD_ANA (1.3V)
    Powering both ends of a potentiometer to GND and VDD_ANA respectively and connecting middle point wiper to GPAINx pins I was able to read values between 6 to 1004 for GPAIN1-3 (channels 3 to 5) but only from 6 to 724 on GPAIN0 (channel 2)
    Documentation says that "NMOS pass gates won’t pass signals with voltage greater than VDD_ANA – Vt"
    so that means that Vt = 0.36V = 1.3*(1004-724)/1004