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TPS563209

eli
Guru 13485 points
Other Parts Discussed in Thread: TPS563209

1)      Have some issue with TPS563209 transient load response (Vin=5V, Vout=3.3V, Iout=1A à 2.5A).

When simulate with webanch, got  Vout drops by 0.1V to 3.2V.

Datasheets show much better response.

How can I improve it (tool dosen’t allow increasing Cout)?

  • 0
    TI__Guru**** 191445 points

    TPS563209 uses DCAP2 control.  Fast transient response is achieved by the adaptive on time control which allows the duty cycle to adjust instantly to load transients without the lag of voltage and current mode control.  In most cases you should not need to increase the capacitance above the recommended amount.  Can you tell me the slew rate of your load step?  Can you post your webench results?

  • 0 in reply to JohnTucker
    Guru 13485 points

    As you can see, Vout drops by ~200mV which is a lot!

    I can’t increase output capacitance because Webench doesn’t allow it.

    6712.ORPAK TPS563209.pptx

  • 0 in reply to eli
    TI__Guru**** 191445 points

    I tried WB yesterday.  I did notice the the slew rate is extremely fast.  That can affect the voltage drop.  I'm meeting w/ the WB team to day to look into this.  I'll let you know.

  • 0 in reply to JohnTucker
    Guru 13485 points

    Hi John

    Any news/feedback?

    B.Regards

    Eli

  • 0 in reply to eli
    TI__Guru**** 191445 points

    Yes I did look into it.  I thought that I posted, but it looks like it did not take (probably my attached graphic caused it).  I will post this without the graphic and just explain it.  Anyway, the slew rate and load step default in WB is fast slew, large step.  You can adjust that by cliking on the current sink in the WB simulation.  Then you can change the properties.  I used 25% to 75% step.  For the EVM I set the load slew rate to 500mA/usec, but the actual slew rate is slower due to inductance in the wires.  It is probably closer to 100 mA / usec.  If you make those changes, then the step response will look close to the EVM waveform.  You can also change the output capacitance in the original WB design schematic.  You are limited in choices so you will have to choose "custom" component then add your own C and ESR.  The sim will reflect those changes.  let me know if you have further difficulties with this.