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ADS7809 - how to indicate when data is valid after conversion?

Michelle Ferment
Intellectual 1440 points
Other Parts Discussed in Thread: ADS7809, ADS8509

On the ADS7809 A/D converter. Running in external clock mode, it's not obvious when the data is ready using read after conversion. What would be the best way to indicate data valid? Would it be on the next rising edge of the external clock after the sync pulse goes low, or on the next external clock after the external clock where the sync pulse is high?

  • 0
    TI__Expert 6925 points

    Hello Michelle,

    Please note the ADS7809 is not recommended for new designs, so I encourage you to use its upgraded version the ADS8509.

    The output register should contain valid converted data if:
    1) /BUSY output goes low after the “initiate conversion” is acknowledged,
    2) And both /CS and (R/C) are high before /BUSY returns to high state. 

    Then, while keeping R/C high, the data can be read with the clock “falling edges” after /CS falls.

    Since the SYNC pulse is 1-clock wide, the first falling edge should be ignored, and then, the following 16 falling edges should provide the converted data.

    Regards,