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BQ24297 STAT odd behaviour

Rich_MTL
Prodigy 60 points
Other Parts Discussed in Thread: BQ24297

We are currently working on a design with a BQ24297 and if we have the battery disconnected then the STAT output flashes around 20Hz  (?) on the STAT output.  

Edit:  We notice that this only happens when the 'CE is pulled low with no battery connected.  Also the output is as shown in screenshot.

During test we need to operate the board without any control from the processor to test the board then to add a single cell and check its charging ok.  Once we connect the battery the device behaviour goes back to normal.

Is it possible to operate the device with CE pulled low and no battery connected whilst still supplying a steady output

?

Any thoughts appreciated

Rich

  • 0
    TI__Expert 3160 points

    Rich, 

    The BQ24297 should be able to function correctly in the test you describe.

    The spike on the STAT scope capture you show indicates to me that this might be something else going on with your board.  Since STAT is an open drain pin, what is it pulled up to in your system and can you take a capture of that?  What is the SYS node look like?

    Thanks,

    Rachel

  • 0 in reply to Rachel Moore
    Prodigy 60 points

    Hi Rachel

    Thanks for your quick reply - just to clarify this scope plot is the output on the power rail side of the inductor attached to SW 19,20 - not what I expect it to do :) - we can repeat this on 3 boards.

    Cheers

    Rich

  • 0 in reply to Rich_MTL
    TI__Expert 3160 points

    Rich, 

    Agreed that's an unpleasant surprise--let's see if we can find the cause. 

    I know you're doing this to test stand-alone operation, but are you able to read registers 0x08 (System Status) and 0x09 (New Fault) for our troubleshooting purposes?  Also, do you have a schematic you can share with me to check? Can you also tell me what is happening on your VBUS pin and SW pin?

    Thanks,

    Rachel