ADAU1702 hysteresis settings

    Hello,

    This is going to appear a bit strange, but you can get the LP filter without hysteresis by selecting the fourth choice, 11 -- No Low Pass Filter.  At least, that's what my informal frequency response and waveform tests show.

•     Frequency Response:

    Three settings (below, right) out of the four have similar responses:

00 -- 4-bit Hysteresis

01 -- 5-bit Hysteresis

11 -- No Low Pass Filter

    The odd one out is 10 -- No Hysteresis, which yields a full frequency response:

•     Waveform:

    By sending a low-frequency (0.2 Hz), low-amplitude (about -20 dB) sine wave to the Aux ADC, its hysteresis response can be seen.  Two settings, 10 -- No Hysteresis and 11 -- No Low Pass Filter, place no hysteresis on the sine wave:

    The 00 -- 4-Bit Hysteresis and 01 -- 5-bit Hysteresis settings place increasing hysteresis on the ADC output:

    Thus, to get a LP filter without hysteresis, choose (ironically), 11 -- No Low Pass Filter.

BTW -- the Capture Window correctly shows the ADC control bits from the selections in the 170x / 140x Register Control window -- so any discrepancy appears to be in the silicon vs. data sheet, not in SigmaStudio.

     Best regards,

     Bob

    Hello,

    This is going to appear a bit strange, but you can get the LP filter without hysteresis by selecting the fourth choice, 11 -- No Low Pass Filter.  At least, that's what my informal frequency response and waveform tests show.

•     Frequency Response:

    Three settings (below, right) out of the four have similar responses:

00 -- 4-bit Hysteresis

01 -- 5-bit Hysteresis

11 -- No Low Pass Filter

    The odd one out is 10 -- No Hysteresis, which yields a full frequency response:

•     Waveform:

    By sending a low-frequency (0.2 Hz), low-amplitude (about -20 dB) sine wave to the Aux ADC, its hysteresis response can be seen.  Two settings, 10 -- No Hysteresis and 11 -- No Low Pass Filter, place no hysteresis on the sine wave:

    The 00 -- 4-Bit Hysteresis and 01 -- 5-bit Hysteresis settings place increasing hysteresis on the ADC output:

    Thus, to get a LP filter without hysteresis, choose (ironically), 11 -- No Low Pass Filter.

BTW -- the Capture Window correctly shows the ADC control bits from the selections in the 170x / 140x Register Control window -- so any discrepancy appears to be in the silicon vs. data sheet, not in SigmaStudio.

     Best regards,

     Bob