• State
  • Locked Locked
  • Replies 5 replies
  • Subscribers 63 subscribers
  • Views 216 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

BQ76952: BQ76952: The IIC transaction to BQ76952 had not completed

BQ76952: Power management forum

Star Xu
Genius 9645 points
Part Number: BQ76952

Hi

When driving bq76952, I found that the response of IIC is very unstable. After sending the device address 0x10, sometimes there is a response, sometimes there is no response, most of the time there is no response, and the communication is unsuccessful.

Attached the part of schematic

The cpu and the device are connected through the isolation chip, after the isolation chip is removed, directly connected, the phenomenon is the same.

please give some suggestions.

Thanks

Star

  • 0
    TI__Guru* 81034 points

    Hi Star,

    Can you try reducing the pull-up resistor values from 10k to 5k to see if it helps? In the waveforms it looks like SCL is not always reaching the full logic level.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    TI__Genius 9645 points

    Hi Matt

    Thanks for your reply.

     The pull-up resistance has been changed to 5.k, 2k, 4.7k. I have tried all of them, but the waveform remains unchanged.

    Waiting for your reply. 

    Thanks

    Star

  • 0 in reply to Star Xu
    TI__Guru* 81034 points

    Hi Star,

    That is strange. What is the clock frequency on the SCL pin? It looks like the speed changes in the first waveform. 

    Are all of the timing requirements in the datasheet being followed? How much time is there between I2C transactions? Are the voltages stable on REG18, REG1, REG2, and VCC3.3?

    Regards,

    Matt

  • 0 in reply to Matt Sunna
    TI__Genius 9645 points

    Hi Matt

    Thanks for your reply.

    The clock frequency is 400k, sometimes there is a response after sending the device address, sometimes there is no response.

    When there is no response, the first five clock waveforms are abnormal, and there is no response when sending data.

    REG18 is 1.8v, the pull-up resistor VCC 3.3V is normal, and REG1 and REG2 have no voltage output.

    Thanks

    Star

  • 0 in reply to Star Xu
    TI__Guru* 81034 points

    Hi Star, 

    It is hard to tell from the scope capture, but is the SDA setup time meeting the specification. SDA must be ready 100 ns before the rising edge of SCLK. The scope capture and logic analyzer data almost look like the host is trying to use the falling edge of SCLK instead of the rising edge.

    Also, can you try to run the I2C at 100 kHz to see if the problem still shows?

    Regards,

    Matt