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TCA9554: TCA9544

Kailyn Chen
Genius 9560 points
Part Number: TCA9554


Dear,

Using TCA9544, 2V  power supply, and our customer find that why the INT couldn't pull up to high level and stay 0.9V with 10Kohm pull up resistor？ When changed to 1K, it is normally.

According to the source current of datasheet, we could caculate the  resistor value about 1K,  and the datasheet recommend 4.7Kohm. I think the rise time should be slower but could get to high level  if connect to 10Kohm, but now it stay 0.9V, please give me some advice?

Best regards

Kailyn 

  • 0
    TI__Guru* 78111 points

    Kailyn,

    The only thing at our INT pin is a NMOS. This means the INT pin is either high impedance or LOW from that pin.

    Are there any other devices connected to the INT pin? 0.9V seems high for a NMOS driver.

    Does this happen with only 1 unit or multiple units and multiple boards? The only thing I could think of which is causing this is if our device was somehow damaged. Can you try replacing this device with a new one?

    Thanks,

    -Bobby

  • 0 in reply to BOBBY
    TI__Genius 9560 points

    Hello Bobby，

    The INT  is open drain output and the customer pull up resistor to VCC, I am sorry that now the phenomenon  is  the INT is  0.2V  when pull up

     10Kohm resistor, ,and it is 1.9V when pull up 1Kohm.

    Kailyn

  • 0 in reply to Kailyn Chen
    TI__Guru 62920 points

    Hi Kailyn,

    It sounds like there may be some leakage current on this net of the PCB that is pulling towards ground.  (This could be due to the INT input of the device connected to TCA9544, for example.)  For equivalent load currents, the lower resistance value helps to produce a lower voltage drop across the pull-up resistor (meaning that the net's voltage with respect to ground is higher).

    Max