[SI-LIST] Re: ESR too low?
- From: "Russel Hughes" <Russel.Hughes@xxxxxxxxxxxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Tue, 8 Nov 2005 09:23:35 -0000
Have you tried putting a 1K Ohm resistor in parallel with the output of
the regulator?, I know SMPS supplies do not like having no load to see.
We use low ESR caps with SMPS regs snd have no problems, but they are
under constant load.
Russ
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Fasig, Jonathan L.
Sent: 07 November 2005 19:30
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] ESR too low?
Can anyone speak to the issue of bulk capacitor ESR being so low that it
affects the stability of the voltage regulator? I have a system with a
well-know commercial 1.5V SMPS powering a board that was populated with
numerous very-low ESR bulk caps. The transient response rings
beautifully
for step load currents and the phase margin (supply+board) is typically
less
than 10 degrees (GM<4dB). At certain low load currents the regulator
oscillates spontaneously at 1.3KHz. When these low-ESR caps are
replaced or
removed, the transient response settles nicely and phase margin
approaches
30 degrees (GM>12dB) but ripple magnitude is affected.
Discussion or references appreciated.
Regards,
jf
------------------------------------------------------------------------
Jonathan Fasig Email: fasig.jonathan@xxxxxxxx=09
Mayo Foundation=20
4001 41st Street NW=20
MSC Sn 2-132 Phone: (507) 538-5464
Rochester, MN 55901 Fax: (507) 284-9171
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