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Original question:

ADS8686S: ADS8686 ADC outputs repeated readings of the first sequence

ADS8686S: Programmable LPF Questions

RJ
Intellectual 2550 points
Part Number: ADS8686S

Hi Team,

For ADS8686S, it has a build in 2nd order anti-alias low pass filter, but the datasheet said “the programmable LPF options are available in the software mode of operation”, what this mean when the chip is in hardware mode?

The LPF would be bypassed? Or LPF would be default to one specific option, then my next question would be which one? Is there a trick to do can set LPF to be 15kHz in hardware mode? I don’t need to change it at all, but I like it to be set as 15kHz.

Regards,

RJ

  • 0
    TI__Mastermind 45435 points

    Hi RJ,

    In hardware mode, the BW of LPF on ADS8686S depends on the input range you select through HW_RANGSEL1 and HW_RANGSEL0 pins. Please see the following table for the details, for example:

    • If you configure HW_RANGSELx=11 which indicate +/-10V input range, the BW of LPF will be 39kHz.
    • If you configure HW_RANGSELx=10 which indicate +/-5V input range, the BW of LPF will be 33kHz.

    Note that  the LPF_CONFIG[1:0] bits in the LPF_CONFIG register are 000b which is ADC's default status after the ADC is powered up.

    If the 15kHz BW is preferred, you may have to use software mode or external low-pass filter.

    I hope this helps.

    Best regards,

    Dale