The Designer's Guide Community Forum - how to measure phase margin in real chip?

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how to measure phase margin in real chip? (Read 1525 times)

vlado Guest	how to measure phase margin in real chip? Jun 04^th, 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 Community Fellow Offline Posts: 391 Munich, Germany	Re: how to measure phase margin in real chip? Reply #1 - Jun 4^th, 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 Guest	Re: how to measure phase margin in real chip? Reply #2 - Jun 7^th, 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 28^th, 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.

Best Regards,

Art Schaldenbrand

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