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TS5A3157: Control Input Pin (IN) without external pull-up resistor.

Junz Abrar
Prodigy 20 points
Part Number: TS5A3157

Hi All,

I couldn't find sufficient info in the data sheet that could solve my query hence posting it here. Hoping to get an answer. 

I had tested 10 of these ICs under similar conditions and three of them burnt. I am trying to find the cause for only the three ICs burning since all the ICs were subjected to the same operating conditions; Which, I ensure, satisfy the operating conditions mentioned in the Data sheet.

Section 9.2.2 (Detailed Design Procedure) in the data sheet mentions that "IN, by default is pulled low to ground or can be pulled up for an open-drain GPIO". Now this should mean that IN has to be externally pulled down or Up and it is not internally pulled down by default? Correct me if I am wrong. 

If it is not pulled down internally by default, then can the IN pin be left floating? 

In my application the IN was not externally pulled down as I thought it is internally pulled down by default (should have paid more attention) which leaves the pin floating if not a Logic High.

The data sheet doesn't mention if the IN pin can be left to float. I suspect this should be the reason for the ICs to burn and that the one's that didn't burn will eventually burn after some time. Could leaving the IN pin floating be the reason for the ICs to burn or can they be left floating? If they can be left floating, what else could have caused them to burn? 

Looking forward to the answers.

Thanks 

  • 0
    TI__Expert 5660 points

    Hello,

    Welcome to E2E and thank you for the thorough description of your concern.

    This device does not have any internal pull-up or pull-down resistors on the control pins. This means that an external connection to the control pins is required for functional operation of the device.

    Here is a link to a TI training video, Can I leave unused pins floating?, which provides more detail about the necessity of ensuring a defined state for the switch with the control pins. These pins should never be left floating unless there is an explicit indication in the datasheet that there is an internal pull-down connection on the control inputs.

    I agree with your suspicion that this is a problem in your system. Please make sure that you have tied these pins to a logic high or low and feel free to reach out if you have any additional questions.

    Best regards,
    Kate

  • 0 in reply to Kate Dickson
    Prodigy 20 points

    Thank you so much for the response Kate.