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TLV743P: EN pin burned

zhang ping
Genius 3835 points
Part Number: TLV743P

Pull the EN pin to the VIN, and the VIN is not higher than 5V. Now there are more than 10 tlv743 output problems in 50 sets. Take down the tlv743 for measurement, and the EN pin and GND are open circuit. Now I consider using the voltage divider in en, but there is no value of IEN in datasheet. How large is the voltage divider suitable? Whether the value of CIN cout needs to be adjusted.

  • 0
    TI__Mastermind 18466 points

    Hey Zhang, 


    IEN is about 0.01uA, but for the worst case scenario assume IEN = 0.1uA.
    You would want to set the resistor divider about 10x to 100x greater than that current.

    The capacitor contributes to the RC delay, so the delay you wish to have depends on the value of your capacitor.

    For the part to work, make sure the VEN value stays less than 0.3V above VIN - as the capacitor will discharge when there is no presence of VIN.


    As for the parts with output problems verify there is no overvoltage events during startup, load transient (inductance causing a spike), and shutdown.  

    Best,

    Juliette

  • 0 in reply to Juliette
    Prodigy 20 points

    hi Juliette&zhang

    I'm the client,The problem with TLV74333 is that the ENpin is short with GNDpin（almost）,the resistance values between EN and GND terminals is about  0.3Ω-400Ω。

    Can you help me guess what is causing this problem.

     

    Thanks

     

    zju

  • 0 in reply to z ju
    TI__Mastermind 18466 points

    Hi Zju, 

    Would you happen to have any scope shots of the event?

    Does EN go high before VIN goes high? What is the layout of the PCB you are testing on?

    Best,

    Juliette

  • 0 in reply to Juliette
    Prodigy 20 points

    HI Juliette&Zhang:

    The oscillograph is shown below: (1 turn on,2 turn off)

  • 0 in reply to z ju
    TI__Mastermind 18466 points

    Hi Zju, 

    If purple is your enable, then Enable going high before VIN is not the issue. 

    During this time, output is off or is the output oscillating?

    Best, 

    Juliette