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BQ24259: I2C multi-write/ poor source question

Ann_Lien
Genius 14360 points
Part Number: BQ24259

Hi expert,

My customer has a question on muti-write function. They want to know if multi-write command would be kept in IC once Stop bit is not sent to IC. If no, how many commands would be kept? For example, does the previous 5 commands would be kept if we want to send 6 commands to IC and I2C pull up power drops when we send the sixth command?

Another question is about poor source. They used a power supply (4.8V) and series a 40ohm/5W resistor. They put loading 30mA then VBUS drops to 3.6V. MCU received interrupt from INT pin then read REG09[5:4]. But they found out there is still 0b00. May I know if our test procedure is right or not? Or poor source detection is not like what we think about?

Thanks for your help and best regards,

Ann Lien

  • 0
    TI__Guru**** 165886 points
    Ann,

    Regarding the I2C multi-write, I will have to check with design next week after the US holiday, early next week.

    Regarding the poor source detection testing, the test method should work but dropping to 3.6V is too close to I2C UVLO (assuming no battery is connected). Poor source is VBUS >3.6V but < 3.9V. Can they increase the power supply or lower the resistor so that VBUS sees ~3.7V to 3.8V?
  • 0 in reply to Jeff F
    TI__Mastermind 25800 points
    Hey Ann,

    In regards to the I2C multi-write, sending a STOP command will stop the I2C transaction.

    You can refer to Figure 26 in the datasheet. The letter "P" refers to the I2C STOP condition. You can write to each successive register up until that STOP command.


    Regards,
    Joel H