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Original question:

TPS62827: Output voltage discharge

TPS62821: Sudden Open Circuit at VIN pin

Francesco Anzalone
Prodigy 110 points
Part Number: TPS62821

Hello,

In my configuration, EN pin is shorted with VIN pin, as shown in the figure. 

For contacting issues in my prototype, it is possible that the 5V line suddenly becomes an open circuit, bringing VIN and EN pin to ground as C2 discharges.

Could this be a problem for output discharge? Or could this even damage the IC internally?

I ask because I noticed that when I've had this type of issue on the 5V line, the 3V3 line (output) was shorted to ground, and I'm wondering if such short may have been due to an internal damage of TPS62821.

Thank you

  • 0
    TI__Mastermind 19290 points

    Hi Francesco,

    I am not sure if I understand the issue completely. 

    Can you please re-attach the schematic and layout. I cannot open it now.

    "For contacting issues in my prototype"- Could you explain the scenario in detail.

    Regards,

    Febin

  • 0 in reply to Febin
    Prodigy 110 points

    Hello Febin,

    Here is the schematic:

     

    My scenario is the following:

    I have two separated boards, called board A and board B. The circuits in the schematic is placed on board B, while the 5V line comes from an USB port on board A. Therefore, the 5V line is brought from board A to board B through a couple of male-female (header-receptacle) connectors. Since I'm working on a prototype, the mechanics of the whole system is not optimized and sometimes the aforementioned connection from board A to board B fails. Therefore, the 5V line at the input of the circuit shown in the schematic, suddenly  becomes an open circuit.

    My question is: may this issue be the cause of an internal failure of TPS62821?

    Moreover, I noticed that when such issue happened, the output voltage (measured at TP1) was not the expected 3.3V, but actually there was a short circuit between the output and ground. Therefore I am wondering if such short is caused by an internal failure of TPS62821.

    Thank you

  • 0 in reply to Francesco Anzalone
    TI__Mastermind 19290 points

    Hi Francesco,

    Thank you for the details!

    When the Vin is cut off, the charge on the Output cap can flow in the reverse direction and causes power loss in the HS FET that inturn damages the FET. If you measure a short, then the device could have been damaged already.

    It is not advisable to have failure in the Vin as it could damage the IC and also this impact is dependent on the circuitry on the input side.

    Regards,

    Febin