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TPS565208: questions about EN-pin . when is the R3(10kΩ) necessary?

Xinhao Liu
Prodigy 60 points
Part Number: TPS565208

According to Datasheet , this diagram above is typical app.

I feel confused for R3(10kΩ) which is cast between EN-Signal and EN-pin.

I have two questions:

1. on dataSheet Pin Description Page.3 . for EN-pin it says : "Enable input control. Active high and must be pulled up to enable the device."

how to pull up ? is this 10kΩ resistor for pull-up?

2. I use WEBENCH to design.

Design report is followed. this design does not have the 10kΩ resistor

so When should we use this 10kΩ resistor? when is it unnecessary? 

  • 0
    TI__Intellectual 1801 points

    Hi Xinhao,

    You can directly pull up EN pin to Vin without a resistor. For further questions, please let me know.

    Regards,

    Jared.

  • 0
    TI__Expert 7500 points

    Hi Xinhao,

    It is okay to directly connect EN to VIN like Webench shows. And can also pull up EN to other source which higher than EN high level voltage and lower than 17V, typically, 5V or 3.3V are both okay.

    Thanks,

    Lishuang

  • 0 in reply to Jiandong Liu
    Prodigy 60 points

    Jiandong Liu said:

    Hi Xinhao,

    You can directly pull up EN pin to Vin without a resistor. For further questions, please let me know.

    Regards,

    Jared.

    thank you for your reply. I got your answer , but I still have a doubt.

    On the diagram of typical app in Datasheet , it clearly recommends the additional R3(10kΩ) resistor, Let me ask a clear question:

    what is the the R3(10kΩ) used for ?

    Then I would make a choice in my own case.

  • 0 in reply to Lishuang Zhao
    Prodigy 60 points

    thank you for your reply. I got your answer , but I still have a doubt.

    On the diagram of typical app in Datasheet , it clearly recommends the additional R3(10kΩ) resistor, Let me ask a clear question:

    what is the the R3(10kΩ) used for ?

    I wonder the reason of the resistor's existence, then I would make a choice in my own case.

  • 0 in reply to Xinhao Liu
    TI__Expert 6425 points

    Hi Xinhao, 

    This resister is a limited current resister which is used to protect IC EN pin in case there is a spike voltage to damage IC EN pin. 

    In datasheet diagram, EN pin is connected by another power supply. In case there is a spike voltage in power supply after a long line which cause IC EN pin damage, so there is a resister in EN pin. 

    in Webench, EN pin is connected by Vin pin, because there is large input cap near Vin pin. There is no spike voltage.  so there is no EN resister in Webench schematic. 

    in summary, please it is based on your circuit to decide if it's necessary to add this resister. 

    BRs, 

    Edwin. 

  • 0 in reply to Edwin Zang
    Prodigy 60 points

    This answer really helps me.

    Thank you very much for your clear and detailed answer.

    Have a good day.