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BQ78350-R1: unknown command sent to charger

Nicolas Bouquet
Intellectual 490 points
Part Number: BQ78350-R1
Other Parts Discussed in Thread: BQ78350, BQSTUDIO,

Hello,

I have a board that works quite fine since a couple of hours with BQ78350-R1 + BQ7692000PW. After spending some time doing some stuff, I noticed that the BQ78350 wasn't responding anymore to bqstudio. The scope was probing the SMBus, trigering on I2C addr 0x12 (charger), the last frame sent from BQ78350 to BQ24725RGR is :

0x16 0xEF

This command is not documented in the charger's datasheet

The BQ78350 is now not responding. Vreg is 3V (not 2.5V) when pushing the start button and the system auto-shutdown after a few seconds.

Any ideas ?

Thanks

  • 0
    TI__Guru* 81035 points

    Hi Nicolas, 

    You mentioned Vreg is 3V? The BQ7692000PW should have a regulator output of 2.5V. Are you sure you have the correct part number on the device? There are other part numbers in the same family that have a 3.3V regulator output. (BQ7692002, BQ7692003, BQ7692004). 3V is beyond the Abs Max input for the BQ78350-R1 VCC input.

    0XEF is not a valid command, so maybe the device was going into Shutdown during the transaction?

    Regards,

    Matt

  • 0 in reply to Matt Sunna
    Intellectual 490 points

    Hi Matt,

    Yes, 3V :) And I'm sure the device is exactly BQ7692000PW. Sometime the multimeter shows 2.5V, sometimes 3V. Probing this signal at the scope shows that the 3V is not very stable. Since something may has gone wrong with the grounds during test, the active devices may have been partially damaged. I should receive some new IC on tuesday, thanks to your sample service!

    Nicolas

  • 0 in reply to Nicolas Bouquet
    TI__Guru* 81035 points

    Hi Nicolas,

    Yes, that does sound like the device must be damaged. I think installing a new IC should fix the issue.

    Matt