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BQ27Z561-R2:SDA pin does not become 0V

user1567465
Prodigy 250 points
Part Number: BQ27Z561-R2
Other Parts Discussed in Thread: BQ27Z561, , EV2400

BQ27Z561's SDA pin become 2V when master access 0x55 address(BQ27Z561 7bit I2C address).

Why does not the SDA pin become 0V?
Pullup resistor is 10kOhm at the SDA pin.

Best Regards,

  • 0
    TI__Mastermind 20920 points

    Hello,

    Can you please confirm that your MCU supports clock stretching? It seems like the MCU is not recognizing the start condition (SDA falling edge while SCL is high) here .

    Regards,

    Anthony Baldino

  • 0 in reply to Anthony
    Prodigy 250 points

    Dear Baldino san

     Thank you for your reply.
     We use nRF5340 made Nordic Semiconductor.
     The nRF5340 is supported for clock stretching (non I2C compliant).
     Please refer to the below.
     

     We tried changing from BQ27Z561-R2 to BQ27421 on the same I2C line.
     Result, I2C communication is correct from nRF5340.
     
     Is there a difference between BQ27Z561 and BQ27421 in I2C communication?

     We returned to BQ27Z561 and connected to the EV2400 on the same I2C line.
     Result, I2C communication is correct from Battery Management Studio via the EV2400.
     

     Could the nRF5340 support for clock stretching (non I2C compliant) be the cause of BQ27Z561's SDA pin does not become 0V? (become 2V.)
     In that case, how should we use the nRF5340?

    Best Regards,

  • 0 in reply to user1567465
    TI__Mastermind 20920 points

    Hello,

    The main difference between the I2C communication of the bq27z561 and the bq27421 is the 100kHz rise time value, with bq27z561 being 1000ns and bq27421 being 300ns:

    bq27z561:

    bq27421:

    I believe the issue lies in the structure for the bq27z561 not matching this structure found below due to how these parameters are set:

    Regards,

    Anthony Baldino

  • 0 in reply to Anthony
    Prodigy 250 points

    Dear Baldino san

     Thank you for your reply.
     I found out the cause.
     nRF5340 output configuration is CMOS, not Open Drain.
     We set the Open Drain.
     Please refer to the below.
     
     I2C communication is correct.

    Best Regards,