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Power on sequence on ADS7828

TOSHIMICHI YAMADA
Prodigy 60 points
Other Parts Discussed in Thread: ADS7828

We have a question on power-on sequence on ADS7828.

In our case, 8ch analog inputs are used for monitoring various analog DC signals.

During power-on sequence on ADS7828, some of these monitoring signals are already active before VDD supply.

That means, strictly speaking, analog inputs would be over VDD+0.3V in booting, because VDD starts from GND in power on.

 

Would ADS7828 accept such over-voltage input conditions in power on sequence?

According to absolute maximum ratings, digital input voltage to GND doesn’t allow to over VDD +0.3V.

  • 0
    TI__Mastermind 22950 points

    Hi Toshimichi-san,

    You are correct in that an analog input above VDD + 0.3V should not be applied. My advice is to avoid this situation as best as possible. The internal diode structure can typically handle 10mA of current but again, this should be avoided as this continuous operation can negatively impact the device's long-term reliability. 

    Perhaps a switch or mux can be added on the inputs of the device to avoid this situation but I do not know your application. If you can give us more information on the application and possibly a schematic, we can discuss some possible solutions. 

    Regards,
    Aaron Estrada