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TPS552882-Q1: spice model caapacitor applied the Simulation

Chul Kim
Intellectual 260 points
Part Number: TPS552882-Q1
Other Parts Discussed in Thread: TPS55288

I have a question about PSPICE simulation.
When I put an ideal capacitor on the TPS55288, I get a clean output waveform as shown below.
Figure 1(yellow dotted line)

However, when I simulate the TPS55288 with the spice model of the actual capacitor, when the output capacitor is above a certain value (176uF), the simulation data shows a switching (1.2MHz) spike voltage caused by the parasitic parameter of the capacitor, and the overshoot and undershoot are not visible under load trend.
(It doesn't look that big in the actual test).
However, if you zoom in on the spikes as shown in the figure below, you can see the overshoot and undershoot.
Figure 2(reddotted line)

Questions
1) Is this switching spike voltage a model issue with the TPS55288, as it is not when I add a real capacitor?
2) Do other DCDC simulations show the same phenomenon if I apply a lot of spice models of the capacitor?
3) Is the switching spike voltage negligible, and if so, why?

  • 0
    TI__Mastermind 27750 points

    Hi Chul,

    Thanks for reaching out.

    Please see my comments below.

    1. The switching spike is caused by PSpice model of capacitor as you used, for the PSpice model provided by capacitor vendors, it contains ESL and ESR parasitic parameters, and it will cause spike voltage due to high frequency switching. You can find more information from below app note. Measuring and Understanding the Output Voltage Ripple of a Boost Converter

    2. Yes, in other DC/DC models, with capacitor spice model, you will also observe spike voltage especially in Boost converters.

    3. Yes, in simulation, it can be negligible, and I think it is not consistent with real test result. As the simulation doesn't contain all parasitic parameters on the switching loop, and also the driver of TPS55288 is ideal which is very fast. So, in real test, the spike voltage would be much smaller than that.

    If you have more questions, please let me know.

    Regards,

    Bryce