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TPS5420: TPS5420 INRUSH

SWENGWOO LEE
Intellectual 270 points
Part Number: TPS5420
Other Parts Discussed in Thread: TPS2375

HI

When setting the TPS5420 to have a 34V input voltage and a 12V output voltage,

you may experience inrush current during power-up.

Is there a way to eliminate this?

  • 0
    TI__Expert 5290 points

    Hi 

    Do you have the schematic for us to check? What is the load condition for the waveform you captured? Also is 34V the maximum input voltage? As TPS5420 is a 36V device with 40V absmax, please make sure the voltage you applied on the Vin pin of the IC is within its limit.

    Regards,

    Hongjia

  • 0 in reply to Hongjia-Wu
    Intellectual 270 points

    HI

    VSUP : 16~34V

    VOUT : 12V

    *Attach the circuit diagram

    *No-load state output voltage and current waveforms

  • 0 in reply to SWENGWOO LEE
    TI__Expert 5290 points

    Hi 

    The current seems to be less than the image you shared earlier. The inductor current is necessary to build up the voltage on the output capacitor. And during the startup, it looks like the SS ramps a little quick initially and large duty cycle is created to let the inductor go high. Will this phenomenon affect your system design? Or you just want to understand what's going on?

    Regards,

    Hongjia

  • 0 in reply to Hongjia-Wu
    Intellectual 270 points

    HI

    The initial picture I posted shows the current input for POE power.

    After negotiation between the PSE and TPS2375, a DC/DC converter is used to generate 34V, which is then applied with voltage using TPS5420.

    However, when TPS5420 outputs 12V, current limit is triggered by inrush from TPS2375. Is there a solution to this?

  • +1 in reply to SWENGWOO LEE
    TI__Expert 5290 points

    Hi,

    I think you need to take a look at TPS2375 as well. From the startup waveform of TPS5420, the behavior looks good to me. Suggest you can create another post titling TPS2375 and the experts from their team will help you.

    Regards,

    Hongjia