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TPS25982: About start up slew rate

Part Number: TPS25982

Hi team,

We have few question about this device design.

In datasheet figure Figure 46. Input Line Transient and Output Short-Circuit Response shows two type start-up "current limited" and "dVdt limited".

 Q1. Does this mean the slew rate set by CdVdt is adapted when start up at input voltage applied and retry from thermal shutdown and current limited start-up is adapted when fast-trip asserted?

We use this device for 19Vin and capacitive load 1400uF. So we set TdVdt over 300msec to prevent thermal shutdown asserted by inrush current.
We are considering this Tdvdt is affect load transient characteristic when steady state.

If dvdt limited slew-rate affect load swing response, we think switching Cdvdt after PG asserted is effective to improve load swing response.

 Q2. Do you have any information about designing information switching Cdvdt circuit or notes?

Best regards,

teritama

  • Hi Teritama,

    Sorry but I could not understand the questions.  But what I can share is:

    1. dvdt cap does not play role in device performance during steady state.

    2. dvdt cap can only control slew rate during startup of device. 

    3. If during startup of device load is higher than current limit then device will start in current limit fashion and not in dvdt manner. 

    Regards

    Kunal Goel

  • Hi Kunal,

    Sorry for my unclearly question.

    I wantted to know difference between current limited start-up and dvdt limited start-up. I understood this.

    Addition, I understood dvdt cap is not affect during steady state.

    dvdt cap doesn't affect device performance during steady state is because of red circle FET in below function block diagram?

    Best regards,

    teritama

  • Hi Teritama,

    DVdt cap does not affect device performance during steady state because GATE is already charged and FET is enhanced. DVDT comes into picture when GATE starts charging up from 0V.

    Regards

    Kunal Goel