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BQ25892: I2C communication lost after Fast Charge phase

Hernan Olave
Prodigy 30 points
Part Number: BQ25892
Other Parts Discussed in Thread: EV2400

Hello,

I'm testing a custom board with the BQ25892, it is charging and monitoring a 18650 cell. So far, everything is good until I configure the IC to a Fast Charge phase with a > 4 Amp charging current, I've configured the corresponding registers in order to not limit the input or the charging current of the battery. The IC is working properly and reporting every 1 second during the pre-charge phase and also in the Fast Charge phase but with the default current charge parameter, after I configure it to charge above 4 Amps, the IC continues charging but the I2C stops working and I don't receive any response from the IC.

To recover from this status, i have to disconnect everything and reconnect it again.

Note: I'm using a laboratory PSU with 12V@3Amps.

  • 0
    TI__Guru**** 166626 points

    Hi Hernan,

    I am not aware of an I2C problem with the IC.  Can you send a oscope plot of your SCL and SDA signals when I2C works and when it doesn't?  How are your I2C lines laid out relative to the SW node, PMID, SYS and BAT traces/planes/pours?  Could there be a noise problem?

  • 0 in reply to Jeff F
    Prodigy 30 points
    Hi Jeff,

    I don't have an oscilloscope at the moment to see the I2C signals, but they are with a pull-up 1k resistor to 3.3v and functioning as expected with other devices and with this IC when is not charging with a high current. This design and power planes are based on the Evaluation board (this problem occurs with the EVM also), therefore I don't think it is a noise problem. The communication is only lost when I change the registers of the charging current.

    Regards.
  • 0 in reply to Hernan Olave
    TI__Guru**** 166626 points

    Hernan,

    I just tested an EVM using TI's EV2400, with 3.3V pull up voltage, and can communicate up to 5A.  When you communicated with the EVM, were you using the EV2400?

  • 0 in reply to Jeff F
    Prodigy 30 points
    Hi Jeff,

    I'm not using the EV2400. I'm using an SAM3S-EK2 board, I did some testings today and when I activate a high current charging, my I2C communication collapses for every device connected to it, so I'm thinking that is something to do with the microcontroller.

    Regards.