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TPS92692-Q1: TPS92692-Q1 burn out when no load connect

Betty Guo
Expert 7300 points
Part Number: TPS92692-Q1
Other Parts Discussed in Thread: TPS92692

Hi team,

customer use TPS92692-Q1 for LED backlight. they have a prolem is when power up, TPS92692 will burn out with out load. if they connect laod, it is ok.

our question is does the TPS92692-Q1 have open load detection ? if no, how to protect device ?

one more question, I see add a diode on the DIM/PWM pin, why place a diode? can remove it? I ask this because customer use PWM control found when PWM will pull down power.

I attached customer schematic, please help check.

  • 0
    TI__Mastermind 18890 points

    Hi Betty,

    What diode are you talking about on DIM/PWM?  I do not understand your question or see a diode on the DIM/PWM. 

    The OVP is for protection when there is no load.  The voltage on the output need to be set such that it does not exceed the max rating of the part 65V.  Please read data sheet for that or use the Excel spread sheet that you can down load from the TI web page below under the Design Tools and Simulations.

    They are using an PNP (Q2) for the PWM Dimming instead of a PFET.  We recommend them to use a PFET.  Please read the data sheet on the Buck Boost design on page 41 to page 46.  In that section we also have the OV protection.

    There's also and evaluation board that the customer can use to help with the development.

    https://www.ti.com/tool/TPS92692EVM-880?keyMatch=TPS92692&tisearch=Search-EN-everything&usecase=GPN

    https://www.ti.com/product/TPS92692?keyMatch=TPS92692&tisearch=Search-EN-everything&usecase=GPN

    Thanks Tuan

  • 0 in reply to Tuan Tran74
    TI__Expert 7300 points

    Hi Tuan,

    The diode I mentioned is D_DIM, you can see it in the datasheet 

  • 0 in reply to Betty Guo
    TI__Mastermind 18890 points

    Betty,

    That diode is for external PWM Dimming input to override the internal PWM dimming duty cycle generated by the two voltage dividing resistor for RDim1 and RDim2.  Another word if there is no external Vctrl then it's the voltage on the DIM/PWM pin generated by the voltage divider that control the duty cycle and it will be internally generated PWM dimming. 

    In general, you do not need this diode if you have external PWM dimming and can have the PWM dimming signal go straight into the DIM/PWM pin with the appropriate voltage.

    Thanks Tuan