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BQ24158: BQ24158 I2C write/read issue

Chung SENLIN
Prodigy 80 points
Part Number: BQ24158

BQ24158YFFT I2C register write and read issue.

We found the write data and read data are not the same and below is my write/read process, register and data.

1. Write BQ24158 register 0x02, data 0xb6,

2. Read Bq24158 register 0x02, data is 0x8E

I attached the I2C write/read waveform for check, please help to review the I2C waveform, thanks.

Mark

  • 0
    TI__Guru*** 143910 points

    Mark,

    Are you writing to the watchdog timer?  If the watchdog expires, the registers return to default values.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 80 points

    Hi Jeff,

    We trigger the watchdog timer every 25sec.

    Could you provide write and read I2C waveform of BQ24158 to me for double check the timing and sequence?

    Thanks.

    Mark

  • 0 in reply to Chung SENLIN
    TI__Guru*** 143910 points

    Hi Mark,

    This behavior is expected. Writing B6 to 0x02 sets VBATREG=4.40V.  If the safety limit register has maximum charge voltage set to 4.20V (default), the charger will automatically clamp VBATREG=4.20V (which is 8E).  If you want to set VBATREG = 4.40V, you have to first set the max battery voltage to 4.40V in register 6.  Register 6 must be the first register written after power up from either VBUS or BAT (CSOUT).  It resets to default if V(CSOUT) drops to ~2.1V.

    Regards,

    Jeff