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Closed loop stability in Eldo

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elmolla

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eldo .lstb

Hey,

Anyone knows how to measure the closed loop stability and phase margin in Eldo or any of Mentor tools without breaking the loop??
 

ch1k0

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lstb + eldo

use .lstb statement
works good, look manual
 

    elmolla

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trashbox

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measure open loop gain with eldo

Why do you need check the closed-loop's PM? Generally, the phase margin is for open-loop.
 

elmolla

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loop gain simulation eldo

Thanks ch1k0.

trashbox, the PM is a measure of the closed loop response speed. We usually prefer our phase margin to be 60 degrees to have good speed without ringing response.
 

elmolla

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lstb middlebrook

There is something weired with the .lstb command
I added the zero source and tried the .lstb command

Sometimes it works and others not! Is there any condition or special simulation setup for it to work out?
 

ch1k0

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stability analysis eldo

only works single loop. has bug if wrong version eldo. tried another version?
 

gafsos

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.extract command in eldo

hi,

.lstb Vlstb

VLSTB NET30 VMOINS DC 0 AC 0

* .lstb This command improves the analysis of circuit stability.
* The .LSTB command measures the loop gain by successive injection (Middlebrook
* Technique). A zero voltage source is placed in series in the loop: the first pin of the voltage loop
* must be connected to the loop input, the other pin to the loop output.


.AC DEC 10 1 1e10
.tran 1n 1n
*.PROBE ac lstb_db lstb_p V(****)

*extracts for open-loop analysis
.EXTRACT AC LABEL = gain_dc YVAL(lstb_db,1)
.EXTRACT AC LABEL = phase_margin YVAL(lstb_p,extract(gb_product))+180
.EXTRACT AC LABEL = gb_product XDOWN(lstb_db,0,1)
.EXTRACT AC LABEL = tau 1/(2*3.14159*extract(gb_product))


IT WORKS
hope that's helpful

Gafsos
 

sutapanaki

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differential loop stability probe

Has anyone found a way to do .lstb for differential circuits? Breaking a differental loop will require two voltage sources.
 

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