• State
  • Locked Locked
  • Replies 5 replies
  • Subscribers 34 subscribers
  • Views 636 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.

PCA9535: Default register value error issue after power-on

JH Shin
Guru 11010 points
Part Number: PCA9535

Hello,

My customer has intermittently issue with default register values changed when reading after power-on of the PCA9535.

They did not control the I2C data and when reading the register values after power on, meaningless values were read.

It occurs 1~2 times out of 10 times, and it operates normally if the register values are modified to the default values.

Please advise on the cause of the problem.

Have there been any reports of similar issues with the PCA9535?

Thank you.

JH

  • 0
    TI__Guru 72901 points

    Do have you scopeshots of the Vcc power up ramp rate when the the registers are not in the default state?

    I suspect there may have been a bad power on reset, most the time when this occurs it is because Vcc does not power up from GND but something higher like 300mV or the ramp rate is too slow.

    -Bobby

  • 0 in reply to BOBBY
    Guru 11010 points

    Hi Bobby,

    Thank you for your help.

    Here is the capture image of the VCC power-up when the registers are no in the default state.

    The customer said that the capture image did not differ between normal and abnormal.

    Please help us to solve the problem.

    Regards,

    JH

  • 0 in reply to JH Shin
    TI__Guru 72901 points

    HI JH,

    Can you provide a schematic of the PCA9535 for me to check?

    How many units/boards does this issue occur on?

    Are you doing any temperature testing with the device before power up?

    -Bobby

  • 0 in reply to BOBBY
    Guru 11010 points

    Hi Bobby,

    Here is the customer's circuit.

    This symptom occured with MP products and there was no temperature testing.

    The customer used 5 PCA9535s in one system, 3 applied to the main board and 2 to the sub board.

    The symptom only occurs with 2 PCA9535s on the sub board and occurs 1~2 times out of 10 power-ups.

    Regards,

    JH

  • 0 in reply to JH Shin
    TI__Guru 72901 points

    Hi JH,

    I don't see anything wrong with the schematic.

    Can you send me an email at duynguyen@ti.com 

    I think we can get in touch with our quality team to see if we can run the failed devices through the ATE program to see if they pass. 

    -Bobby