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ADS124S06: ADC Data conversion (initial) time

Sky
Prodigy 20 points
Part Number: ADS124S06

We are using ADS124s06 ADC. Measurement is in continuous mode with the data rate of 4000SPS and we are using the low-latency filter.  As per our understanding from the datasheet,  reading data from one channel is possible at a time. So we have to set the channel in INPMUX register  to switch between the channels and read the measurement values. In Page 42 of the datasheet, it is mentioned that there will be a delay of 0.406 + programmable delay for the first data and 0.25+programmable delay for the subsequent readings.  Since we are switching between multiple channels of the same device (in continuous mode ), we would like to know if the first data delay appears each time when we switch the channels.

For example:

Step1 : Send the START command to acquire in continuous mode.

Step2:  Set the channel 0 and 1 in differential mode and wait for the required time and read the data -> It will take 0.406 ms for the first data

Step 3: Set the channel 2 and 3 in differential mode -> Whether this is considered as the first reading or subsequent reading? Will the initial delay of 0.406ms be applicable here due to changing channels?

Thanks

  • +1
    TI__Guru** 113765 points

    Hi Sky,

    Welcome to the E2E forum!  When using the low-latency filter, the correct timing guide to follow is Table 13 in the ADS124S06 datasheet on page 42.  When changing channels, the digital filter is reset and will respond to the timing of the FIRST DATA column in the table.  The SECOND AND SUBSEQUENT column only reflects the timing if there is no configuration register changes.

    When changing the configuration (which would include gain, data rate, reference, etc.) the FIRST DATA column would apply.  Note also that note 3 will need to be added to the time which relates to the Programmable Delay.  The programmable delay is used to reduce analog settling error and the default delay is an additional 14tMOD periods.  So the total time with the default delay would be (104 + 14) tMOD (or 460.94us).

    If you take multiple conversions using the same input channel and device configuration, then the SECOND AND SUBSEQUENT column would apply and you would not add in the programmable delay.  The programmable delay only applies to the first conversion following a configuration change (see section 9.3.6.3 in the datasheet) while in continuous mode.

    Also be aware that when using the internal oscillator there could be some variation in the timing due to initial frequency and possible drift over temperature.  Another thing to be aware of is the filter is reset following the decoding of the register write of the configuration change(s).  For additional information see the WREG section 9.5.3.12 on page 68 of the datasheet.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 20 points

    Dear Bob,

    Thanks for the information