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Original question:

ADS7828 to monitor DC voltages

ADS7828: DC characteristic proper details not available in Datasheet

balasubramani r
Expert 1170 points
Part Number: ADS7828

Hi There,

While checking the datasheet some details are not available like VOH ,Acquisition time. Can anybody share the details. Want to have it for dc analysis.

  • 0
    TI__Mastermind 24970 points

    Hello.

    The VOH is your VDD power supply .

    The acquisition depends on what communications mode you will be using. The below figure shows the beginning of the acquisition time at the 4bit of the command byte until you begin reading.

    Note, in High speed mode, the clock is pulled low by the device until you are able to read out the results.

    Regards,

    Cynthia

  • 0 in reply to Cynthia
    Expert 1170 points

    Hi Cynthia,

    Im planning to use this IC for thermistor based temperature sensor. So for this ADC IC we may use Fast Mode and High speed mode for this but not sure. If there source resistor and by pass cap is fixed then the acquisition time may get vary depends on mode we choose. Also do we need to have any special filter for this analog input. We thought of using RC filter but it will indirectly affect the acquisition time. Can you provide some suggestion here. 

  • 0 in reply to balasubramani r
    TI__Mastermind 24970 points
    Hello,
    Usually thermistors are slow changing, thus is depends on your desired sampling rate and throughput to decide if Fast mode of High speed mode should be used. The RC filter also depends on your source and sampling rate.
    Would you please share your proposed input signal source and target sampling rate and throughput?
    Regards,Cynthia
  • 0 in reply to Cynthia
    Expert 1170 points

    Hi Cynthiya,

    We are planning to use either standard or fast mode for our application. Is there any possibilities to change the sampling rate? since datasheet not having much details compare to other datasheet. 

    For now considering 50KHz Sampling rate and through put @400KHz. 

    Attaching circuit for reference purpose. 

  • 0 in reply to balasubramani r
    TI__Mastermind 24970 points
    Hello,
    Thank you for your schematic.
    You can use a clock at 400kHz, and get a throughput of 8kHz, the RC filter you have works well.
    Since you are using It for DC analysis, you don't need to use the 3.4MHz clock for a throughput of 50Khz.
    If you would like use the 3.4MHz clock for a 50KHz throughout then you will need to reduce the R43, 10K resistor, probably within the hundreds. Though with DC analysis there is no need to go that fast.

    Regards
    Cynthia