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ADS131E04: ADS131E04 and ADS8861 synchronize together

Will Wang47
Expert 7780 points
Part Number: ADS131E04
Other Parts Discussed in Thread: ADS8861, , ADS8363, ADS8556, ADS8910B

Hi team,

My customer Qunling is working on a project. In this project, they get four signal need to be sampled, one high speed signal, grid current、voltage、one slow dc signal. And the high speed signal need to have 5us time resolution, so we recommend ADS8861, which is 1MHz ADC. And for the left three signal, they need sample at same time, so we recommend ADS131E04, which has 4 ADC inside, could do simultaneous sampling.

Now they need to synchronize those two ADC together. This means that they want to know the four signal value at the same time, and they need to display them. And according to your rich experience, do you get a way to achieve this? And for the signal measure, do you have any better solution or parts to achieve this?

Thanks and Best Regards,

Will

  • 0
    TI__Guru 55342 points

    Hello Will,

    Thanks for your post!

    There are a couple of things to consider here.

    Typically one of the best ways to synchronize multiple devices is to use the same clock source. This is an issue for the proposed design since the ADS8861 only uses an internal clock and there is no option (that I am aware of, I support Delta Sigma architecture devices) to output the internal clock of the ADS8861 to the ADS131E04.

    Additionally, the delay for the data output of the ADS131E04 will be much greater than that of the ADS8861.

    Are they hoping to measure transients using the ADS8861? Is this for protection purposes or only diagnostics?

    Using a 4ch simultaneously sampling SAR or 4 1ch SAR's may be a more viable approach here depending on what the customer is trying to accomplish.

  • 0 in reply to Alexander Smith
    TI__Expert 7780 points

    Hi Alex,

    Thanks for your reply.

    Actually the high speed signal is a PWM signal, they want to detect the slope, and the rise time and fall time error need to lower than 5us, so 1Msps data converter is preferred. And as far as I know, we don't offer one part that has 4 channel 1Msps simultaneously sampling SAR adc, am I right? 

    Thanks and Best Regards,

    Will

  • 0 in reply to Will Wang47
    TI__Guru 55342 points
    Hi Will,

    Happy to help! The ADS8363 looks to be close, but it has an input structure that I am unfamiliar with. From the description it looks like it may only be capable of two simultaneously sampling channels.

    Do you know what level of resolution the customer is designing for?

    Finding a single channel SAR with a flexible clocking/Daisy-chaining scheme may be the best option.
    www.ti.com/.../products.html

    I'm looping in someone from the SAR team for additional guidance - Luis may be able to provide a better recommendation.
  • 0 in reply to Alexander Smith
    TI__Expert 7780 points

    Hi Alex,

    Appreciate your help. And looking forward hear from Luis.

    Best Regards,

    Will

  • 0 in reply to Will Wang47
    TI__Guru 55466 points
    Hi Will,

    The ADS8363 is a dual simultaneous sampling ADC. It has a 4x2 multiplexer, therefore the user can only simultaneously sample 2 channels at a time. Other devices in the portfolio such as the ADS8556 offer 6-channel simultaneous sampling; however sampling rate is limited to 630kSPS.

    Since they require to sample the 4 signals simultaneously at 1-MSPS, one option is to use 2x ADS8363 devices and connect the CONVST signals together. This will allow them to synchronize precisely the sampling of the (4) signals. Alternatively, you could also use 4x ADS8861 devices, (or 4 x ADS8910B devices) connecting the CONVST signals together. On SAR ADCs, the sampling of the signals is controlled externally by the CONVST pin. Although an internal conversion clock is used to perform the conversions, the sampling of the signals is directly controlled by the rising edge of CONVST.

    Thanks and Regards,
    Luis
  • 0 in reply to Luis Chioye
    TI__Expert 7780 points

    Hi Luis,

    Appreciate your help.

    Regards,

    Will