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ADS114S06B: Digital Filter Settle Time

Russell Wetherley1
Expert 4255 points
Part Number: ADS114S06B

Hello E2E,

I am using the ADS114S06B to support two separate sensors at a time.  I will have to ping-pong between the two sensors during operation.  This will entail switching IDAC connections (and current value), external reference connections and PGA input connections.  At the moment, my concern is settling time of the RC input filters and the digital filters in the ADS114S06B.  I am using the internal clock and continuous conversion mode with an output data rate of 20 samples/sec.  What I would like to know is, neglecting RC input filter settling, how long does it take to settle the digital filters after starting continuous conversions?  In other words, how many output samples should I discard before starting to believe the data?

Thanks!

Russell

 

  • 0
    TI__Guru** 113765 points

    Hi Russell,

    When you change certain register settings the conversion will restart which also flushes the digital filter.  The registers (addresses 0x03 through 0x07) that trigger a new conversion are listed in the ADS114S06B datasheet in section 9.5.3.12 (WREG).  So the length of time to first conversion following a mux change, for example, will depend on the data rate being used.  In any case the first DRDY falling edge after the register write will have settled data with respect to the digital filter.  So you don't need to discard any samples with respect to the digital filter.  Take a look at the Data Conversion Time listed in Table 7 of the datasheet.  The timing is shown in Figure 62.

    From Table 7 we see that at 20sps the first conversion after the register change would take 56.559ms and the data are valid at that time.

    Best regards,

    Bob B