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BQ4050: I2C communication

Pakho
Prodigy 195 points
Part Number: BQ4050


Tool/software:

Hi TI team,

We have met some issues about i2c communication with BQ4050. When the issue happened, the data pin has been pulled low abnormally. But we don't know why.

Abnormal:

Normal:

Schematic,

Please kindly share your comment about this issue.

  • 0
    TI__Mastermind 29155 points

    Hi Pakho,

    What is being sent to the gauge when the issue is occurring? Is this the only command that causes this or are there others?

    Regards,

    Anthony

  • 0 in reply to Anthony
    Prodigy 75 points
    • The BQ4050 sends addr:0x0b reg:0x3d and then the first data it gets is 0x78, then the data line pulls low. as shown：Page 7.

    I2C.docx

    • We also have a slave 0x3c led_driver hanging above this I2C. Initial analysis 0x78 (0b01111000) is considered 0x3c+w by led_driver. because actually see led_driver show exception
    Arrow backward
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  • 0 in reply to ?? ??
    TI__Mastermind 29155 points

    Hello,

    Thank you for confirming, in the schematic above it seems like the communication lines are attached to 1M Ohm pull down resistors. The SMBC/SMBD pins are open drain for this device, so they will need to be pulled up externally for correct function. Can you please confirm why these are attached to pull down resistors?

    Regards,

    Anthony