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ADE7854A brownout behaviour

Category: Hardware
Product Number: ADE7854A

Hi ADE experts,

how does the ADE7854A AFE behave if the VDD supply voltage decreases unintendedly during operation?

As I read the datasheet, when VDD falls below 2.5V, the AFE enters an inactive state and stops measuring.

Between 3.3V and 2.5V, will the measurement accuracy be compromised? Or can the measured values be trusted as long as it is working?

Thanks for your support!

Markus

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  • In a brownout condition if the voltage falls below the por (power on reset) voltage all the registers will be default and will need to be reconfigured. Por is listed as 2.5V but there is some tolerance. Performance is only guaranteed to 3.3 +/-10% or 2.97 to 3.63

    Why is the voltage falling below 2.97V ? If your power supply is failing the micro need to determine what to do.  increasing storage capacitance will give you mare time for house keeping before the por. 

    Dave

  • Hello Dave,

    thank you for the quick response.

    After a period of producing metering products without problems we are now facing a quality issue with the isolated supply of the metering AFE part. Some of them possibly are not able to keep the supply voltage of the AFE high enough. Unfortunately the system MCU has no feedback about the isolated supply voltage level - except that the AFE is able to communicate. 

    And we are now concerned that the meter calculates wrong energy values while we are not aware of it. So my hope is that as long as the AFE seems to be working, it calculates energy values correctly.

    Or do we definitely have to expect unreliable energy values at a supply voltage level below 2.97V?

    Thanks again!

    Markus

  • Since we have not tested below the 2.97V for performance I really can't say how good the measurement is. That being say this is something you could  test in your system. You could vary the supply to the ADE7854A and see if any of your measurements change. 

    We do expect some level of regulation to our parts. This seems like you need to get a new supply rather than see if the ADE7854A will work with a bad supply

    Dave

Reply
  • Since we have not tested below the 2.97V for performance I really can't say how good the measurement is. That being say this is something you could  test in your system. You could vary the supply to the ADE7854A and see if any of your measurements change. 

    We do expect some level of regulation to our parts. This seems like you need to get a new supply rather than see if the ADE7854A will work with a bad supply

    Dave

Children
  • Okay, thank you. Our first approach is of course to have a reliable supply again.

    Since there are already products in the field which potentially could have this problem we would like to know what to expect from these anyways.

    Thanks,

    Markus

  • The only thing you can tell for sure is the part reset looking at the run register is good for this. there is also the checksum register to see if any register changed value. In this case all the registers are default values and everything is meaning less. If the registers are what you expect when the supply is in range the datasheet spec is valid. I do not have the information for the performance out of the vdd +/-10% 

    Dave