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how to measure phase margin in real chip? (Read 5106 times)
vlado
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how to measure phase margin in real chip?
Jun 04th, 2004, 1:10am
 
Hi, I need to measure phase margin in real chip. It is low drop out regulator and i need to know how stable is that circuit. Open loop measurement isn`t so exact, i thing...
thanx
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Frank Wiedmann
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Re: how to measure phase margin in real chip?
Reply #1 - Jun 4th, 2004, 4:20am
 
Do you mean measurement in the lab or simulation? If you mean simulation: Spectre 5.0 has a stability analysis (stb) that keeps the loop closed. If you mean measurement in the lab: take a look at http://www.venable.biz/tr-papers2.html.
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vlado
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Re: how to measure phase margin in real chip?
Reply #2 - Jun 7th, 2004, 2:11am
 
i mean real measurement in lab, SPICE simulation is quit simple, but in real it is problem.
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sheldon
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Re: how to measure phase margin in real chip?
Reply #3 - Dec 28th, 2004, 6:08pm
 
Vlado,

  Never measured phase margin on the bench so it is a good question. Have you tried putting in a small square wave, need to avoid slew rate limiting, and looking at the overshoot? You should be able to infer phase margin from small signal overshoot. Don't remeber the formula for conversion, it is in most textbooks, Gray and Meyer and Allen.

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