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BQ78350-R1: Charging issues

vinay kambappa
Prodigy 160 points
Part Number: BQ78350-R1
Other Parts Discussed in Thread: BQSTUDIO

I have observed that the IC allows charging only when I connect the IC to system via EV2300, I have grounded the Pres pin so that the FETS are enabled by default. What could be the reason for this behavior? How to config the IC so that it does charging and discharging without being connected to BQstudio?

  • 0
    TI__Guru* 81034 points

    Hi Vinay,

    Are you using an EVM or a different board? The device should not need to be connected to BQStudio to enable the FETs. Have you set the [FET_EN] bit in the Mfg Status Init register?

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 160 points

    I am using the different board. So FET_EN should be set, for auto charge and discharge? Yes, it is set but still I observe the same behavior.

  • 0 in reply to vinay kambappa
    TI__Guru* 81034 points

    Hi Vinay,

    Can you share your schematic? Also, can you read all of the Safety Alert and Safety Status registers to see if there are any protections that are triggering?

    Thanks,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 160 points

     Pres is actually pulled low on the board always, and when I connect to Bqstudio it shows DSG and CHG fet high. But when I disconnect form bqstudio the Vgs=0 on charge FET. No faults observed. I will share the screenshot of the SafetyStatus.

  • 0 in reply to vinay kambappa
    TI__Guru* 81034 points

    Thanks Vinay. Yes, please share a screen shot of your registers after you reconnect BQStudio. There must be a reason the CHG FET is disabled. Also, I do not see on your schematic where the PRES pin is pulled low - there is a signal to the PRES pin, but it also has a pullup to VCC.

    It would help if you can share the Registers screen, the data flash settings for your device, and the schematic for the SMBus pins (this schematic does not show where they are connected and the pull-up resistors).

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 160 points

    Registers

    Data memory

    Although in schematic the pres pin is not pulled down I have made the changes externally on the board. Also wanted to know if the SMBUS lines need to be pulled high always, because in the design we don't have pull ups for smbus, since there is pull up in EV2300. So is it necessary to have pull ups to enable FETS?

  • 0 in reply to vinay kambappa
    TI__Guru* 81034 points

    Hi Vinay,

    So only the CHG FET is disabled when you disconnect the EV2300? In your FET Options register, the SLEEPCHG bit is set to zero. This means the CHG FET will turn off with the device is in SLEEP mode. If you want to change this behavior, you can set this bit high.

    Best regards,

    Matt