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TPS2493: current limit

Denny Huang
Expert 7170 points
Part Number: TPS2493

Dear team

For current limit, I refer EQ1 from datasheet page.7. For Rsense is 22m ohm, the ILM is 2.27A

But the GATE turned off when input current reach 2.86A. It's different of the value of calculation(2.27A).

Could you help to explain about this issue.

ILM = 50mV/22m ohm

        = 2.27A

The waveform as below:

Ch1 : Iin

CH2 : GATE

Ch3 : Vcc

CH4 : Vo

The schematic as below: 

Many thanks

Denny

  • 0
    TI__Guru** 105361 points

    Hi Denny,

    What is the test condition for that test waveform ? Is it during Vin power-down?

    Can you please share better resolution schematic image.

    Best Regards, 

    Rakesh

  • 0 in reply to Rakesh
    TI__Expert 7170 points

    Hi Rakesh

    The schematic image as below.

    Test condition : 

    Rsense is 22mohm Result.

    Connect to electric load.

    sink load at Initial current 2.5A and Vin power-down when current up to 2.8A(slowly load on from 2.5A)

    Many thanks

    Denny

  • 0 in reply to Denny Huang
    TI__Guru** 105361 points

    Hi Denny,

    Why Vin is powering down? Is it due to current limit of the input power supply ?

    Can you please share test waveforms (including timer voltage) to understand more.

    1. Vin, GATE, Timer, Input current

    2. Vout, GATE, Timer, Input current

    Best Regards, 

    Rakesh

  • 0 in reply to Rakesh
    TI__Expert 7170 points

    Hi Rakesh

    The test waveforms as below, could you help to recommend?

    Vin, GATE, Timer, Input current

    Vout, GATE, Timer, Input current

    This experiment is to change Vin to be supplied by dc power supply instead of PSA , and it will not OCP if electric load sink 3.5A.

    Many thanks

    Denny

  • 0 in reply to Denny Huang
    TI__Guru** 105361 points

    Hi Denny,

    Thanks for the test waveforms..

    Couple of observations.

    1. Timer waveform and pattern looks very odd. 

    2. GATE and Vout are at same level.. means FET is OFF but the question is why Vout is not dropping ?

    Have you tested at no-load ? 

    Use resistive load for testing. Some electronic load behave weird during fault modes.

    Best Regards, 

    Rakesh