The -12V in the TBolt is not used for the serial port. the HIN232 of the TBolt goes from the +5V only, it generates the + and - by the usual switched capacitor technique common to other RS232 interfaces (ADM232, MAX3221 and so on). The -12V powers the LT1014 quad precision opamp that I presume handles the EFC, so care must be taken about the -12 although the PSRR of the opamp comes to the rescue.
On Thu, Nov 24, 2011 at 8:25 PM, <[email protected]> wrote: > When you design a regulator, lots of gain is not a criteria in the error > amp. (Who needs microvolt accuracy?) High gain generally means two gain > stages, which in turn makes it difficult to compensate when driving > reactive loads. Thus most op amps are generally a bad idea for an error amp > in a regulator. > > Noise needs to be defined. Generally it means broadband noise. But if your > regulator is on the verge of oscillation when the load current or line > voltage changes, who cares if the broadband noise is low? > > This thread is starting to baffle me. Simply dig up a low noise regulator > chip. LTC comes to mind. Or troll the net for audiophile shunt designs if > you are going to roll your own. > > What you see done in design often is dubious. Just because it is built, > doesn't mean it is good. (Hey, there are doctors that give bad medical > advice.) You need to evaluate existing designs for your application. > > It pays to read the datasheet religiously. Some of these high accuracy > regulators can't handle low ESR caps on the output. > -----Original Message----- > From: Joe Gwinn <[email protected]> > Sender: [email protected] > Date: Thu, 24 Nov 2011 10:14:35 > To: <[email protected]> > Reply-To: Discussion of precise time and frequency measurement > <[email protected]> > Subject: Re: [time-nuts] Low noise power supplies for time nuts circuitry > > At 2:28 PM +0000 11/24/11, [email protected] wrote: > >Message: 3 > >Date: Thu, 24 Nov 2011 13:22:38 +0100 > >From: Attila Kinali <[email protected]> > >To: Discussion of precise time and frequency measurement > > <[email protected]> > >Subject: Re: [time-nuts] Low noise power supplies for time nuts > > circuitry > >Message-ID: <[email protected]> > >Content-Type: text/plain; charset=US-ASCII > > > >On Wed, 23 Nov 2011 04:50:49 -0800 > >Chuck Forsberg WA7KGX N2469R <[email protected]> wrote: > > > >> How well would a pair of cascaded 3 terminal regulators do - say a 7815 > >> feeding a 7812. > > > >78xx Regulators are quite noisy. You can use them to filter the > >noise of a cheap DC/DC converter, but i wouldnt use them feed > >high precision electronics. There are a lot better designs these days. > > What I see done in low-noise circuits is a low-noise opamp used as a > linear voltage regulator to clean up the output of a 78xx or the like > regulator. > > Joe Gwinn > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
