Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > sci.electronics.design > #431081

Re: LDO

Show all headers | View raw

Am 12.10.2016 um 23:35 schrieb klaus.kragelund@gmail.com:

>> I love simulations. What would make me a little bit nervous is the small
>> oscillation at ~235kHz.
> I get the same oscillation. It gets a lot worse when the load kicks in at 300ms
>
> If one add a feedback capacitor from the opamp output to the inverting input of 100pF,
> the oscillation disappears completely. That's the normal way to compensate an LDO,
 > at least how I normally do it :-)

Yes, it is silent then. Reducing the value of R5 also does the job.
I'd like to mention that the load 'step' in this simulation is _very_ 
soft (it takes 10ms to linearly rise the current). DDR RAM would be much 
faster.
If I specify a rise and fall time of 10ns you can see the step in the 
output and further reduction of R5 becomes necessary.
I've set R5=33k and C3=100p and it's ok. With R5=50k it is only silent 
until the load comes in.

Cheers

Robert

Back to sci.electronics.design | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

LDO John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-11 22:09 -0700
  Re: LDO Robert Loos <1209@baer-gmbh.com> - 2016-10-12 09:49 +0200
    Re: LDO John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-12 08:31 -0700
      Re: LDO bitrex <bitrex@de.lete.earthlink.net> - 2016-10-12 22:47 -0400
      Re: LDO John S <Sophi.2@invalid.org> - 2016-10-13 06:16 -0500
        Re: LDO John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-13 08:08 -0700
          Re: LDO Klaus Kragelund <klauskvik@hotmail.com> - 2016-10-13 08:57 -0700
            Re: LDO John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-13 09:05 -0700
            Re: LDO Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2016-10-13 09:26 -0700
              Re: LDO Klaus Kragelund <klauskvik@hotmail.com> - 2016-10-14 04:38 -0700
                Re: LDO Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2016-10-14 07:42 -0700
    Re: LDO klaus.kragelund@gmail.com - 2016-10-12 14:35 -0700
      Re: LDO John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-12 15:58 -0700
      Re: LDO Robert Loos <1209@baer-gmbh.com> - 2016-10-13 08:46 +0200
    Re: LDO Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2016-10-12 15:08 -0700
      Re: LDO John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-12 15:53 -0700
        Re: LDO Winfield Hill <hill@rowland.harvard.edu> - 2016-10-13 03:28 -0700
          Re: LDO John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-13 08:21 -0700
    Re: LDO piglet <erichpwagner@hotmail.com> - 2016-10-13 14:03 +0100
      Re: LDO Winfield Hill <hill@rowland.harvard.edu> - 2016-10-13 06:16 -0700
        Re: LDO piglet <erichpwagner@hotmail.com> - 2016-10-13 14:30 +0100
          Re: LDO John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-13 08:26 -0700
  Re: LDO doggerel <doggerel@nil.com> - 2016-10-12 16:07 +0800
    Re: LDO Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2016-10-12 15:53 +0300
      Re: LDO doggerel <doggerel@nil.com> - 2016-10-13 10:16 +0800
    Re: LDO John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-12 07:35 -0700
      Re: LDO doggerel <doggerel@nil.com> - 2016-10-13 10:15 +0800
  Re: LDO bloggs.fredbloggs.fred@gmail.com - 2016-10-12 08:41 -0700
    Re: LDO John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-12 09:20 -0700
      Re: LDO bloggs.fredbloggs.fred@gmail.com - 2016-10-13 15:52 -0700
        Re: LDO John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-13 16:11 -0700
          Re: LDO bloggs.fredbloggs.fred@gmail.com - 2016-10-13 21:45 -0700
            Re: LDO John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-14 09:05 -0700
  Re: LDO Tim Wescott <tim@seemywebsite.really> - 2016-10-12 11:21 -0500
    Re: LDO John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-12 09:57 -0700
      Re: LDO Tim Wescott <tim@seemywebsite.really> - 2016-10-12 15:11 -0500
        Re: LDO John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-12 16:11 -0700
          Re: LDO Winfield Hill <hill@rowland.harvard.edu> - 2016-10-13 04:52 -0700
            Re: LDO John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-13 08:33 -0700
          Re: LDO Tim Wescott <seemywebsite@myfooter.really> - 2016-10-13 18:21 -0500
            Re: LDO John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-13 20:15 -0700
              Re: LDO Tim Wescott <seemywebsite@myfooter.really> - 2016-10-14 12:35 -0500
          Re: LDO Tim Wescott <seemywebsite@myfooter.really> - 2016-10-13 18:24 -0500

csiph-web