TINA/Spice/TPS54560-Q1: Frequency compensation Evaluation on TPS54560

Harish kumar

Part Number: TPS54560-Q1
Other Parts Discussed in Thread: TINA-TI, TPS54560

Tool/software: TINA-TI or Spice Models

I'm trying to evaluate loop compensation network for TPS54560 using Pspice simulation tool. First I tried by inserting small magnitude ac signal voltage in output loop, getting some weird response, magnitude graph is starting from negative side and approaching zero ( means e2e.docxno 0db crossover, no phase margin).

And then I tried by inserting small ac signal voltage in feedback path (as suggested in datasheet), the magnitude plot is starting from zero itself and phase plot is starting from some negative value.

Any help on this?

over 8 years ago

0 Britt Brooks - Online Design Tools over 8 years ago

TI__Mastermind 41310 points

Harish,

You will need to use the PSpice average model that is located in the product folder under the Tools and Software tab. It can be downloaded and opened and it will show you how to use the average model to simulate the Bode Plot. Do not try to use the transient model for this purpose.

0 Harish kumar over 8 years ago in reply to Britt Brooks - Online Design Tools

Intellectual 435 points

I'm using the pspice average model only but don't know how to add that loop response file.

Have a look on the circuit, am I doing correctly?

And I'm getting the below response.

0 Britt Brooks - Online Design Tools over 8 years ago in reply to Harish kumar

TI__Mastermind 41310 points

Harish,

Why did you remove the injection circuit? You need to have the 1E6 capacitor and the 1E6 inductor in place. You may change the compensation, output cap structure, input caps, and inductor, but you should not remove the injection circuit.

Some of this information is contained in the application notes section on the schematic.

0 Harish kumar over 8 years ago in reply to Britt Brooks - Online Design Tools

Intellectual 435 points

Thanks Britt.

It worked, getting proper results. May I know why high inductor & capacitor are added in injection circuit, are these to create high impedance path between output and feedback loop?

I got one more method to evaluate compensation network (refer below circuit and pspice waveform), same is suggested in TPS54560 datasheet. What is the difference between two approach?

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TINA/Spice/TPS54560-Q1: Frequency compensation Evaluation on TPS54560