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BQ25892EVM-664: Charging current cannot set to 5A

CH Yang
Prodigy 20 points
Part Number: BQ25892EVM-664
Other Parts Discussed in Thread: BQ25892,

Dear Sir:

I am evaluating BQ25892 by doing test on BQ25892EVM-664.

I have problem on charging battery up to 5A.

The input I provide is 12V/3A. 

I use MCU to control BQ25892 through I2C.

I try following setting:

1. Input ILIM set to maximum: reg0x00 -> 0x3f(also tried 0x7f)

2. Fast charge current limit set to maximum: reg0x04 ->0x4f

After I write above registers, charging current goes up to 5A for few seconds, then fall back to 2A.

The status field show no error.

Below are registers change when current drop from 5A to 2A


Read I2C Data :3f 6 8d 1a 4f 13 5e 9c 3 44 73 56 0 57 5f 60 52 e2 30 3f 5

Read I2C Data :7f 6 8d 1a 20 13 5e 9d 3 44 73 56 0 57 5e 5e 52 e2 29 3f 5

If anyone has this experience can provide suggestions?

Thank you.

CH

  • 0
    TI__Guru**** 165886 points
    CH,

    Are you writing to the watchdog timer? If watchdog timer expires, the ILIM pin enable bit is reset as indicated in the second I2C data set. So, input current becomes limited by the lower of ILIM pin resistor setting or I2C IINLIM register setting. Also, I noticed that the battery voltage was close to regulation, which means the IC is transitioning from CC to CV. Once in CV mode, the charge current starts to taper off.
  • 0 in reply to Jeff F
    Prodigy 20 points

    Jeff,

    Thank you!

    It's indeed the watchdog timer issue.

    After setting watchdog timer disabled, the issue resolved.

    CH