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BQ24773EVM-540: No charging current

Ved Soni
Intellectual 530 points
Part Number: BQ24773EVM-540
Other Parts Discussed in Thread: BQSTUDIO

I'm using a BQ24773EVM-540 to charge a battery at 512 mA. It was initially charging fine, however, I had to connect a 10 megaOhm resistor across the battery terminals for some reason, and I tried charging the battery in that manner. However, after doing this, the charge current dropped to zero. Now, even when I'm trying to charge the battery by removing the resistor, there isn't any charge current. I tried setting the charge current by using BQStudio, the device ACK is OK, and I'm able to set the charge current at 512 mA, however, no charge current is being read by the DMM. Also, I tried connecting the charger to an electronic load via a DMM and tried charging it at different currents, however, the charge current is still 0. Is there any way I can reset the IC? Or it is damaged and will I have to get a new one? Thanks!

  • 0
    TI__Expert 5330 points

    Hi Ved,

    If you remove all power from the device by removing disconnecting the adapter (VIN) and battery from the EVM, it will fully reset the part. 

    You might want to try a different battery.  If your battery has a protection IC, there is a chance that you somehow put that IC into a state where it is blocking charging current.  If so, it might be necessary to reset that IC.

    I'm not sure why a 10 megaOhm resistor in parallel with the battery would have much of any effect.  It is possible that an ESD event may have caused IC damage either on the gauge IC or charger during the process of adding it. 

    Regards,

    Steve

  • 0 in reply to Steve Preissig
    Intellectual 530 points
    I'll try disconnecting the adapter. Also, I'm thinking of trying out the checks mentioned in the QSG to ensure that the charger IC is okay.

    My battery doesn't have a protection IC, so I don't think thats an issue. Also, earlier, I used to connect a DMM in parallel to the battery to measure the voltage (which is equivalent to connecting a high value resistor in parallel with the battery) and that never caused any issue with the charging process.

    I'll reply back to you with any more developments. Thanks a lot!
  • 0 in reply to Ved Soni
    Intellectual 530 points

    Hello Steve! I tried the charger starting procedure. I set the input adapter at 19.5 V and the I2C power supply at 3.3 V and verified them both with the DMM. Next, I verified the pin voltages as mentioned in the datasheet. Foll are the results:

    CELL (TP11) - 0V (grounded)

    BATPRES (TP10) - 0V (grounded)

    ACDET (TP7) - 2.6 V

    ACOK is Lit

    REGN (TP15) - 5.3 V

    BAT to GND (J3) - 3.5 V (this should be 1 V as specified in the datasheet)

    ACDRV (TP6) to CMSRC (TP5) - 6V

    SYS to GND (J2) - 4.4 V

    The BAT to GND voltage is higher than what is specified in the datasheet. Is this a cause of concern and how do I fix this?

  • 0 in reply to Ved Soni
    Intellectual 530 points
    Hey, I figured the issue out. Actually, I was using LabVIEW to disable the watchdog timer setting of the BQ24773EVM, but in that process it was altering other bits which were disabling the charging process. I'm not sure why this is happening but I'm using BQstudio now to manually disable the watchdog timer. Sorry for the inconvenience. Thanks a lot!