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TPS4811-Q1: TPS48110-Q1 derived

Meng Liu
Intellectual 1765 points
Part Number: TPS4811-Q1

Hi expert

we have two question:

  1. How to derived this equation? In datasheet page 12

  1. For Inrush current: customer used 400uF load and got two difference value that have big error. the one is calculate though Equation 2 , the other is from test. what can cause this errors？ 

  • 0
    TI__Guru** 101891 points

    Hi Meng,

    1A) The equation is based on the internal circuit design. Is your circuit result not matching with the equation ?

    2A) please share calculated values for your design and actual test result. How much % error you have observed ?

    Best Regards,

    Rakesh

  • 0 in reply to Rakesh
    TI__Intellectual 1765 points

    1):I just interested in how to got 11.9. our design is matched.

    2): in our understood, R1C1 can reduce inrush current because their increase miler clamp so in the customer test, their got the MOS Qg though test turn on time. then they got the Irush but this value have 30% error with datasheet inrush current equation. 

  • 0 in reply to Meng Liu
    TI__Guru** 101891 points

    Hi Meng,

    1A) 11.9 factor is coming from the internal current sense amplifier

    2A) Can you please share the R1C1 values used in the customer design, the MOSFET part number and the inrush current profile with 400uF load.

    Is the inrush current profile/value not matching with the R1C1 calculations in the datasheet ?

    Best Regards

    Rakesh