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TPS2121: TPS2121

CHENWEN WU
Prodigy 10 points
Part Number: TPS2121

Hi, I am using TPS2121 in our design with the following parameters: VIN1 = DC Adaptor  =  5V  , VIN2 = VBUS = Regulated voltage range 4.75~5.25V. Now , CP2 voltage=1.8V,  PR1= 1.3V

Now , i have a problem. When adaptor and USB power are existing. Plug out and plug in adaptor again it will cause TPS2121 output voltage suddenly down over 19ms.  How about my design circuit as below? Is it something wrong? Thank you.

 

  • 0
    TI__Mastermind 32650 points

    Hi Chenwen,

    When both inputs exists, then CP2>PR1 and this means VIN2 will be passed to VOUT. The device should not show any change or any switching behavior as CP2>PR1. The device does not care is PR1 is falling or if IN1 is falling. Could you please confirm the inputs and the voltages and provide a scopeshot that shows VIN1, VIN2, PR1 and CP2 for the same event that describes the VOUT graph above?

    A possible explanation might be that during the unplug and plug event, there is a spike of voltage on the VIN1 rail which causes PR1>CP2 momentarily. This could cause a quick double switching and selection of a rail that is invalid. I would recommend using some sort of noise suppression like a 10nF (max!) capacitor on PR1 or some sort of TVS diode on the VIN1 and VIN2 rails.

    Thanks,

    Shreyas