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TPS40200: Loop Stability Analisys

Other Parts Discussed in Thread: TPS40200

 

Dear Sir or Madam

 

I found that your article “Loop Stability Analysis of Voltage Mode Buck Regulator with Different Output Capacitor Types- Continuous and Discontinuous Modes” (SLVA301) is very interesting and gives very simple and useful method to analyse FB stability. Could you, please advise if you have similar article for Current Mode Control Regulators, as I could not find it. Also I have some questions about this article.

 

  1. I simulated circuit with TPS40200 from the example (Figure 34) in it datasheet. I am using SIMetrix. (See my simulation diagram Fig1 in the attached file). My result (see Fig 2 in the attached file) – Fcrossover=34kHz, Phase=47°- is fully match with datasheet result (Figure 43). Datasheet gives Phase Margin as a Phase value at crossover frequency. But SIMetrix analysis gives Phase Margin 133° - this is equal to subtract of 180° and the Phase Value @ Fcrossover . So where is the correct value?
  2. There is an example of circuit for TPS40200 in this article too, where Vramp=(Vcc/20)-0.15V. But in the Datasheet Vramp=0.1*Vcc. So where is the true?
  3. I also simulated circuit with TPS40200 given on page 17 in this article (see Fig.3 in attached file). As can be seen from Fig.4. in the attached file, my simulation for Gain is exactly match Figure 15 in this article. But my simulation for Phase  (see Fig.5. in attached file) does not match with Figure 15 in this article. Taking in the account that my simulation results fully match with the Datasheet (as I described in p.1) I can not understand this difference

 

8228.For TI .xls

TPS4