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ADS7947: How to configurate unused channel

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Replies: 3

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Part Number: ADS7947

Dear Specialists,

My customer would like to use AD7947 only one channel.

I would be grateful if you could advise how to configure.

I appreciate your great help in advance.

Best regards,

Shinichi

  • Hi Shinichi,

    This is a 2-MSPS SAR ADC with a 2-ch multiplexer.  The device has no registers, and the multiplexer channel is selected using the CH SEL pin.  CH SEL = LOW selects CH0 and CH SEL = High selects CH1.  In normal mode, PDEN is kept low.  If you need to togge CH SEL to change channel, Figure 40 shows the timing for analog Input Channel Selection.

    The device requires a 16-CLOCK frame to read the 12-bit conversion data as shown on the timing Figure 43.  The falling edge of CS triggers the conversions.

    Since this is a  2-MSPS SAR ADC device, the input needs to be driven with a high bandwidth amplifier (or low impedance source). Figure 52 shows the recommended OPA365 in buffer configuration with an RC charge kickback filter at the inputs of the ADC,  and figure 54,55 show the schematic with the necessary supply bypass capacitors and  recommended board layout.

    Let me know if you have questions.

    Best Regards,

    Luis

  • In reply to Luis Chioye:

    Hi Shinichi,

    I forgot to mention, the user may ground the inputs of the unused channel using pull-down resistors.

    Many Thanks and Regards,
    Luis
  • In reply to Luis Chioye:

    Hi Luis,

    Thank you for your reply.

    I understand unused channel input shoud be connected to GND via pull-down resistors.

    I'll share your answer with the customer.

    I appreciate your great help.

    Best regards,
    Shinichi

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