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ADS8862: ADS8862 - Device enters latchup condition after brownout

Part Number: ADS8862

Hello,

A customer of mine has discovered that the ADS8862 enters a latchup condition after a brownout occurs on the AVDD rail.    The problem is reproducible on more than one unit.  

Steps to reproduce latchup:

1. DVDD = 1.8V

2. AVDD = 3.3V

3. After powerup, reduce AVDD below 2V and then bring back into nominal operating condition.

The picture above details the voltage waveform that recreates the latchup.    The blue trace does not latchup, while the green trace does.

Symptoms of the latchup condition include:

1. Increased current draw from AVDD

2. SPI bus becomes unresponsive.

Would you please verify/confirm this behavior on an EVM?  Thanks.

Don

  • Hi Don,

    The AVDD and DVDD have a recommended minimum operating range as mentioned in the table below - 

    If the AVDD supply voltage drops all the way to 0V and ramps up again, then an internal power-on-reset (POR) will be generated and device will function normally. 

    In case when the AVDD supply voltage drops below the minimum recommended operating condition but not all the way till 0V, the POR may not be generated during supply ramp-up. In the absence of POR, one may see higher than normal supply currents. I think this is the situation which customer has encountered.

    It is recommended that supply voltage, after power-up, should be maintained above the minimum operating conditions. 


  • Appreciate the response.

    To confirm:

    1. At power-up the AVDD supply needs to be monotonic, from 0V to the minimum required operating voltage of 2.7V.

    2. Should the supply voltage ever drop below 2.7V, the supply needs to be ramped down to 0V, then brought back up in a monotonic fashion as indicated in #1.

    Correct?

  • Hi Don,

    Yes, your summary is correct.
    When the device supply drops below minimum required operating voltage (either during power-up or normal operation), it is recommended to ramp down the power supply to 0-V and power-up again.

    Thanks.