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TPS61241: Inrush current during startup

Part Number: TPS61241

Hi Expert,

Customer used TPS61241, 5Vout/500mA and see two big inrush spike during startup though the it can power up successfully. 

I saw datasheet mentioned during soft start, the switch current limit is reduced to 300 mA until the output voltage reaches VIN but I don't understand how it trips in the waveforms. 

Would you please comment if it is expected or any issues? Thanks.



  • Hi Allan,

    Thank you for posting. Sorry that our experts supporting this device is currently on the national holidays starting today and they will come back to work after Oct 8th. I am sending them a notice so your question will be taken care of once they are back to work.


    Youhao Xi, Applications Engineering

  • Hi Alan,

    In the first waveform, the LX input current ramps up to around 400mA when Vout reaches Vin. While the datasheet says the device switch current limit is 300mA in this phase. There is some variation for this spec so I think there is no problem for this waveform. As you can see, in the second waveform, when Vout reaches Vin, the device starts switching so inductor current becomes a triangle. The device operates with normal valley current limit of 700mA typically. So waveform 2 also has no issue.