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ADS1015 Ain vs VDD during startup

Dan Andersen
Genius 11460 points
Other Parts Discussed in Thread: ADS1015, TPS2493

My customer is using the ADS1015 to monitor 4 IMON outputs from our TPS2493 (4 of them).  The TPS2493 is the main power input to the system, and is operating off a much higher voltage main input rail (>20V) that it is monitoring.  The ADS1015 is further down the power stream, operating on a 3.3V rail that comes up several ms after the main rail.  This means there may be a few ms where the IMON outputs to the ADS1015 Ain pins could have voltages as high as 3V (max voltage output of TPS2493 IMON output) while the ADS1015 is still powering up.  We note that the absolute max values for Ain are VDD+0.3V per the DS.  Is there a risk of damage to the ADS1015 if the Ain pins are close to 3V as the device turns on?  The IMON out pins of the TPS2493 appear current limited to about 2mA...  I'm assuming the internal ESD diodes will start to conduct when Ain is > VDD, but givent the short time period this might happen and the current limit of the voltage source - will this be an issue?

Thanks,

Dan 

  • 0
    TI__Intellectual 1610 points
    Dan,

    Let me get back to you shortly.

    Thanks,
    Krunal
  • 0 in reply to Krunal Maniar
    TI__Intellectual 1610 points
    Hello Dan,

    Since the absolute analog input requirements are violated, there are a couple of concerns, one is large currents through the ESD protection diodes and another is latch-up.

    The analog input current that these ESD diodes can withstand is 10 mA and hence the maximum input current that can be applied to any analog input is 10 mA. As long as you ensure that the maximum input current is well within 10 mA, you are covered here.

    Another concern is latch-up. There could be internal non-destructive latch-up events which in turn could cause an unexpected behavior. For this reason, I would avoid the inputs exceed the absolute analog input requirements of the ADC.

    Thanks,
    Krunal