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ADS114S08B: Logic output types

Akira Sugimoto
Prodigy 90 points
Part Number: ADS114S08B


Tool/software:

Hello,

Which types are the outputs of ADS114S08B, push-pull or open drain? I am considering desgning wired OR connection for DOUT, connecting multiple devices to a single SPI bus.

Thanks.

  • 0
    TI__Guru 54166 points

    Hi Akira Sugimoto,

    The ADS114S08B outputs are push-pull

    You can connect multiple devices together by combining the DIN, DOUT, and SCLK signals, and then using a separate CS for each device

    Alternatively, you can tie DIN, CS, and SCLK together, and then have separate DOUT lines for each device

    In either case, you would only use a single DRDY line from one device to determine when conversions are complete, assuming you are starting the conversion for each device at the same instant

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 90 points

    Hi Bryan,

    Thank you very much for your reply.

    Is my understanding correct that DIN, DOUT, and SCLK signals can be shared via same bus, and CS and DRDY signals should be used independently each devices (Hence, cannot DOUT/DRDY dual- function output be used for inidicating "data ready")? How about the case that conversions are controlled by commands with keeping the START/SYNC pin low and/or the case that DOUT signals are selected with the multiplexer?

    Akira

  • +1 in reply to Akira Sugimoto
    TI__Guru 54166 points

    Hi Akira Sugimoto,

    Akira Sugimoto said:
    Is my understanding correct that DIN, DOUT, and SCLK signals can be shared via same bus, and CS and DRDY signals should be used independently each devices

    You can use a single DRDY pin, you do not need to use them all. The DRDY pin should transition from high to low at approximately the same time if you start the conversion for all ADCs at the same instant. Therefore, one DRDY pin is sufficient, as long as you add some buffer before clocking out data to account for any small device-to-device delays

    Alternatively, you could use something like an AND gate for all DRDY signals. Then, the AND gate will indicate when all DRDY signals transition from high to low.

    Akira Sugimoto said:
    How about the case that conversions are controlled by commands with keeping the START/SYNC pin low

     Yes this is also fine

    Akira Sugimoto said:
    or the case that DOUT signals are selected with the multiplexer?

    You could do this as well

    There is no one right answer to this question, there are many options you can choose

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 90 points

    Hi Bryan,

    OK. Thank you for the detailed explanation.

    Akira