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TPS54328: PSpice model instability, Webench FSW report

Lenio Cacula
Genius 16660 points
Part Number: TPS54328

TPS54328 is supposed to run with switching frequency close to 700kHz at steady state, but Webench shows in its report a frequency of 644kHz. For this particular application operating conditions are:

Vin = 5V

Vout = 1.5V

Iout = 3.0A

Questions:

1. Why Webench is showing Fsw = 644kHz?

2. Why PSpice TPS54328 model is so unstable with any currents above 1A? With the project straight from the website, the output never regulates to the voltage (in this case 1.05V). The TINA model runs fine though.

Thank you!

  • +1
    TI__Mastermind 26350 points

    Hi Lenio,

    1. FSW is not exactly at 700kHz as it is pseudo-constant and can vary with Vin, Vout and Iout. Check Figure 11 as an example on variation.

    2. Seems like some issue with default configuration options. Please click PSPICE menu -> Edit simulation profile. And choose SPEED_LEVEL as 0 to improve accuracy. That resolves the issue and waveforms look good.

    Thanks,
    Amod