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BQ76952: About the IIC communication problem of bq76952

JH Zhang
Prodigy 220 points
Part Number: BQ76952

Hi ti experts,
When I tested the IIC communication of bq76952, I found that the IIC response ACK time is not fixed. The ACK waiting time is about 30us-120us. Why is this?
I currently design the MCU to use three-wire IIC communication to communicate with the bq76952, but due to inconsistent ACK response times, the MCU cannot communicate with the AFE, which is different from other TI devices.

  • +1
    TI__Mastermind 25980 points

    Hi JH,

    The device may occasionally clock stretch when fetching data.

    Clock stretching is when the peripheral device, in this case the BQ76952, holds the clock line low to indicate to the host controller that it is still processing the current command. Once it is done processing, it will release the clock to indicate to the host that it is ready to move on. The host controller's protocol would require reading the state of the clock line after releasing it to see if the clock is being stretched or not.

    It is required to have an MCU that supports clock stretching when communicating with the BQ76952.

    Table 9-2: Command/Subcommand Operation Time of the Technical Reference Manual contains a list of the approximate processing time of most direct commands and subcommands to see if this delay is expected.

    Regards,

    Max Verboncoeur