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LP5562 / Is it possible to change the state of EN/VCC pin dynamically during another I2C slave device is still communicating on I2C?

K.Yaita
Guru 29720 points
Other Parts Discussed in Thread: LP5562

Hi Team,

My customer uses LP5562 in his system and another I2C slave devices are also connected on the same I2C line(SDA, SCLK).
In this case, I would like to ask following question.

Is it possible to change the state of EN/VCC pin dynamically during another I2C slave device is still communicating on I2C?
He set EN/VCC low when LP5562 doesn't communicate on I2C but he doesn't care any timing requirement of enabling EN/VCC pin.
Is there any timing requirement of EN/VCC pin?

The background of the question is I heard LP5562 holds SDA line low suddenly in his system and my customer is concerning above.

I posted the other day is the same issue.
https://e2e.ti.com/support/power_management/led_driver/f/192/t/521663

Your support would be really appreciated.

Best Regards,
Yaita / Japan disty

  • 0
    Guru 29720 points

    My customer got waveform of the issue occured.
    It shows I2C master send address "1011000(7bit)" but LP5562 falsely recognize "0110000(7bit)", then LP5562 hold SDA line "Low".



    I think the issue is occured by enable timing of EN/VSS pin, so I believe EN/VCC pin shouldn't be changed dynamically during I2C master and another I2C slave device are communicating on I2C(SCL, SDA).
    Is my understanding correct?

    I would like to have your comment.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Intellectual 1985 points

    Hi Yaita,

    There is a timing requirement for EN/VCC in the datasheet.

    You can get the customer to try again, but make sure i2c command is sent 1ms after EN/VCC goes high.

    Regards

    H L

  • 0 in reply to Hak-Leong Ng
    TI__Intellectual 1985 points
    Hi Yaita,

    Somehow the attached image did not show up in previous post. The timing requirement is on page 6, at the end of section 6.6 in the datasheet.

    Regards
    H L
  • 0 in reply to Hak-Leong Ng
    Guru 29720 points

    Hi Hak-san,

    Thank you for your advice.

    >(1) The I2C host should allow at least 1ms before sending data to the LP5562 after the rising edge of the enable line.
    In this case, I2C master intend to send data to another I2C slave and not to LP5562.
    Should I consider that EN/VCC shouldn't be enabled during I2C master and another I2C slave device are communicating on same I2C line?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Intellectual 1985 points

    Hi Yaita,

    I have one LP5562 EVM and another device EVM (lets call it LP88xx, device not release yet) with their i2c lines tie together for testing.

    I can disabled EN/VCC and issue commands to LP88xx, enable EN/VCC and communicate with LP5562. With EN/VCC enabled, I can communicate with both device, just not exactly at the same time because I am not able sync them up nicely with two difference GUIs.

    I think the only time the problems occurs is SCL is toggling within 1ms after EN/VCC goes high. Unfortunately I can't create this condition with 2 separate GUI, I will again next week.

    If customer can avoid any I2C communication on the I2C bus within 1ms after EN/VCC goes high, it should be fine.

    Regards

    H L

  • 0 in reply to Hak-Leong Ng
    Guru 29720 points

    Hi HL-san,

    I appreciate for your continuous support.
    I recommended to avoid any I2C communication on the I2C bus within 1ms after EN/VCC goes high.
    I heard it went well in my customer's system.

    Best Regards,
    Yaita