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TCA9509: About A side ports

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Guru 21045 points
Part Number: TCA9509

Hi Team,

 

We understand that those pullup resistors should not be placed on the A-side ports because TCA9509 has an integrated 1 mA current source.

Therefore, our customer is using TCA9509 at the following conditions.

However, SDAA and SCLA pins remains LOW then DDC signal can’t communicate.

(This phenomenon occurs with a specific device and they have already confirmed A-B-A swap cross check.)

 

Therefore, they would like to know about contents of your shipment test.

Do you confirm that ADAA and SCLA pins are pulled up to VCCA at VCCA is applied?

 


 

Regards,

Kanemaru

  • 0
    TI__Mastermind 49270 points
    Hey Hideto-San,

    Just so I understand the problem completely, are you saying the customer is seeing A side latch low when VccA and VccB are present (on) or just when VccA is on and VccB is off?

    Also, what is the state of the enable pin when you see this issue?

    Thanks,
    -Bobby
  • 0 in reply to BOBBY
    Guru 21045 points

    Hi Bobby-san,

     

    Thank you for your prompt reply.

    This phenomenon occurs when VccA and VccB are present (on).

    And, enable pin is High level.

     

    Regards,

    Kanemaru

  • 0 in reply to Hide
    TI__Mastermind 49270 points
    Hey Hideto-san,

    From the conditions you have stated, you should definitely be seeing the A side pull up to VccA instead of GND which you seem to be seeing.

    -When this happens does it happen immediately when you turn on the device or does it occur sometime during communication?
    -How many boards are you seeing this problem with?
    -If you remove this device and replace it with a new one, does it still see this problem?

    If you are seeing the i2C bus being latched low, the first two possibilities come to mind:

    1) The device could have been damaged when it was placed on the board (possibly ESD related).
    2) The second is the board may have a short to GND somewhere. If this is occurring then I would also expect the B side to pull low as well because the EN is on and A is propagating low to B side.
    -Is B side seeing a low as well?
    -Can you do a continuity test on the A side pins in regard to GND and make sure there isn't a short?



    Can you tell me what is on the top of the IC? There should be a device marking which says 7K, 7KO, or 7KQ depending on which package you have have.

    Thanks,
    -Bobby
  • 0 in reply to BOBBY
    Guru 21045 points

    Hi Boby-san,

    Thank you for your reply.

    I will contact you again after I get new information.

    Regards,

    Kanemaru