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Original question:

BQ27Z561: BQ27Z561 cannot turn on QEN function？

BQ27Z561: external temperature measurement

Ryan Wang
Expert 7465 points
Part Number: BQ27Z561

Dear expert,

After BQ27Z561 power up, it report around 360 degree for the first several seconds. After that , it is normal. Is it as expected? 

What reason might be?

Is it a random temperature? Or always something around 360 degree? Why? 

If external NTC is not connected, I saw around -63 degree is reported. Is there any max limitation for this report data?

If TS short to GND, what is max temperature data might reported?

Customer need these info to avoid their SW report error in mass production.

Thanks a lot

  • 0
    TI__Expert 7465 points

    And how long do they need to wait after BQ561 power up before read temperature?

  • 0 in reply to Ryan Wang
    TI__Guru 57697 points

    Hello Ryan,

    The temperature reading goes through a filter which is based on a few seconds of readings. Instead of waiting ( 5 seconds ), it is better to poll the temperature until it shows the expected value. This will help reduce total time.

  • 0 in reply to Shirish
    TI__Expert 7465 points

    Shirish,

    "filter which is based on a few seconds of readings"

    Do you mean I have to read for several times before to get a accurate temperature? Or wait for 5 seconds is also OK. Just it might waste more time.

    Is this filter to avoid temperature jump?

    Is initial temperature fixed around 36x degree after power up? Is this 36x degree default initial value for this filter?

    What temperature is if no NTC is connected in theory?

    What temperature is if TS short to GND in theory?

  • +1 in reply to Ryan Wang
    TI__Guru 57697 points

    Yes, Temperature cannot change suddenly in real world, therefore the filter. I do not think there is any data on what the temperature will read when NTC is not connected or if TS is shorted to ground.

    Waiting for few seconds is also an option. The 5 seconds is not documented anywhere but is a good guess,  so you will need to check if it works. If the gauge goes to sleep mode almost immediately on power up(almost never configured that way), then it may take much longer.