reg + reference
in [Design]
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From: John Larkin on 26 Mar 2010 18:36 On Fri, 26 Mar 2010 14:34:19 -0700, Joerg <invalid(a)invalid.invalid> wrote: >John Larkin wrote: >> ftp://jjlarkin.lmi.net/V220_reg.JPG >> > >Just curious, why not replace all this with one of these: > >http://www.analog.com/static/imported-files/Data_Sheets/ADR01_02_03_06.pdf > >Much less space, cheaper. Unless you need the 3.3V somewhere. Yes, I need 3.3 to run an ARM processor, 40 mA or so maybe. The ADR could run off the +15, so maybe that's a better way to go. It would cost a little more, but the TC would be a lot better. Maybe I'll do that, the LM1117 for power and the ADR for the reference. Wait! LM4120 will work. +3 ref with 120 mV dropout! John
From: Tim Williams on 26 Mar 2010 18:45 Eww, Eternal September wasn't sending. Or it seemed like it wasn't. Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms "John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in message news:e8cqq59sveanjdpadl7ho0t9h6e50vgots(a)4ax.com... > On Fri, 26 Mar 2010 16:45:37 -0500, "Tim Williams" > <tmoranwms(a)charter.net> wrote: > >>"John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in >>message >>news:ds6qq5pog4jacgoi7fdnunckt584e7emkr(a)4ax.com... >>> I figured using the beta thing would predictably get the geezers all >>> worked up. There's nothing wrong with it. >> >>Ha. And this after pre-coffee pouncing on my designs? >> >>Pot, Kettle, Larkin ;-) >> >>Tim > > Repeating yourself is a sign of impending geezerdom. > > John >
From: John Larkin on 26 Mar 2010 19:03 On Fri, 26 Mar 2010 15:36:09 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Fri, 26 Mar 2010 14:34:19 -0700, Joerg <invalid(a)invalid.invalid> >wrote: > >>John Larkin wrote: >>> ftp://jjlarkin.lmi.net/V220_reg.JPG >>> >> >>Just curious, why not replace all this with one of these: >> >>http://www.analog.com/static/imported-files/Data_Sheets/ADR01_02_03_06.pdf >> > > >>Much less space, cheaper. Unless you need the 3.3V somewhere. > >Yes, I need 3.3 to run an ARM processor, 40 mA or so maybe. > >The ADR could run off the +15, so maybe that's a better way to go. It >would cost a little more, but the TC would be a lot better. > >Maybe I'll do that, the LM1117 for power and the ADR for the >reference. > >Wait! LM4120 will work. +3 ref with 120 mV dropout! > > >John And of course, the LM4120 is a stability land-mine of its own. ThestandardapplicationcircuitfortheLM4120isshownin Figure1.Itisdesignedtobestablewithceramicoutput capacitorsintherangeof0.022�Fto0.047�F.Notethat 0.022�Fistheminimumrequiredoutputcapacitor.These capacitorstypicallyhaveanESRofabout0.1to0.5. SmallerESRcanbetolerated,howeverlargerESRcannot. Theoutputcapacitorcanbeincreasedtoimproveloadtran- sientresponse,uptoabout1�F.However,valuesabove 0.047�Fmustbetantalum.Withtantalumcapacitors,inthe 1�Frange,asmallcapacitorbetweentheoutputandthe referencepinisrequired.Thiscapacitorwilltypicallybein the50pFrange.Caremustbetakenwhenusingoutput capacitorsof1�Forlarger.Theseapplicationmustbethor- oughlytestedovertemperature,lineandload. Thanks, National. John
From: Michael A. Terrell on 26 Mar 2010 19:06 Tim Williams wrote: > > Eww, Eternal September wasn't sending. Or it seemed like it wasn't. Or you're drinking way too much coffee! -- Service to my country? Been there, Done that, and I've got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida http://www.flickr.com/photos/materrell/
From: Jan Panteltje on 26 Mar 2010 19:28
On a sunny day (Fri, 26 Mar 2010 14:24:39 -0700) it happened John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in <ds6qq5pog4jacgoi7fdnunckt584e7emkr(a)4ax.com>: >On Fri, 26 Mar 2010 19:21:00 GMT, Jan Panteltje ><pNaonStpealmtje(a)yahoo.com> wrote: > >>On a sunny day (Fri, 26 Mar 2010 10:19:55 -0700) it happened John Larkin >><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in >><13rpq5lqd1lj1k9flb9orfr2vcl2tuucpi(a)4ax.com>: >> >>> >>>ftp://jjlarkin.lmi.net/V220_reg.JPG >>> >>> >>>John >>> >> >>No money for a real current source or current mirror? >>Does that 1M depending on beta circuit change a lot over temperature? >>Its Vbe will change, so will the Ib. > >The current into the reference will be more constant than if I just >used a resistor with a nominal 0.3 volt drop across it. The BCX71K has >a very tight beta spec. It would probably be better than using the >current mirror discussed in another thread recently. And we have >BCX71Ks in stock for under 4 cents each. It is senile, the base will pick up all the noise it can get from the universe. |