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ADS8556 partial power-down

Keiichi Kajino
Expert 2365 points
Other Parts Discussed in Thread: ADS8556, ADS8555

Hi, folks

 

We observed unexpected phenomena while using ADS8556.

Sometimes the ADS8556 gets malfunction. The CH_A0, A1 or CH_B0, CH_B1 seems stuck.

We can see various combination, only A, only B, A and B were stuck. If we applied POR or Reset, it will retrieve. (We do not use CH_Cx)

 

Could you please let me know how it occurs and how to resolve? Is there any possibility the ADS8556 gets into partial power-down mode even if CONVST_x applies properly? (as NOT partial power-down mode)

 

Also Is there any way to read-out control register value? (I would like to confirm PD_x bits not to flip.)

  • 0
    TI__Mastermind 46265 points

    Dear Keiichi-san,

    Thanks for your post. According to CONVST’s high or low level at the falling edge of the BUSY signal (please refer to the timing below), ADS8556 decides if the corresponding channel pair will go into partial power-down mode or continue next conversion. If enter a power-down mode, the relevant channel pair can  be activated again by issuing a RESET pulse or power up. Please check your digital signals' timing,  sometimes a strong interference signal also can lead to this phenomenon by disturbing CONVST signal even if the software has no problem.

    Also please check your BUSY signal, the BUSY signal will keep low if three channel pairs go into power-down mode.

    If you don't want your ADC to enter power-down mode, you can use ADS8555 which is same as ADS8556 only except no power partial power-down mode.

    Please let us know your check and test results, thanks.

    Best regards

    Dale Li

  • 0 in reply to Dale Li
    Expert 2365 points
    Dale,
    Thanks you for your answer. Also I am sorry to late reply due to holiday season in Japan. I wiil check with customer.