I do most of my designs such that the 5V rail has to supply only a=20 tiny amount of current: 2-10mA. All of the high-current stuff runs=20 from the unregulated supply, either directly or via a switcher. That=20 makes it easy for me to use a reference as my Vdd supply. Question: could you use something like a LM317 as a smart pass=20 device, then control that pass device with an accurate version of a=20 TL431? That would be really inexpensive and is as accurate as the=20 shunt regulator. Note that the feedback into the shunt regulator=20 comes from the regulated output of the power supply. You mention automotive - a reasonable number of my designs are used=20 in either automotive or industrial machinery (24V rail=20 nominal). Keeping the uP power separate from the rest of the circuit=20 works REALLY well in those designs. dwayne At 10:13 PM 11/17/2011, PICdude wrote: >Trust me when I say I've been looking for a regulator accurate enough >(<1% error) so that I can eliminate an external voltage-reference >chip. I need TO-220 though, as the tab gets heatsunk to the >enclosure. I also need 130mA from 13.5V (automotive). So far, >generic 7805's with and external Vref chip (AME385BEETZ or LM4040) is >best solution. > >Cheers, >-Neil. > > >Quoting Dwayne Reid : > > > At 08:53 AM 11/17/2011, Sean Breheny wrote: > >> Thank-you to Joe and all who answered. Since I need better than 1% > >> accuracy, I think I best use a solid external reference :) > > > > If you can tolerate a 5V rail, National Semiconductor's LP2950A is a > > 5.00 Vdc low-dropout regulator with 0.25% initial tolerance at > > 25C. I suspect that others now make similar regulators in lower > > voltages but I don't have manufacturers or part numbers handy. > > > > Many of my designs use the LP2950A regulator when I need a/d accuracy > > of 1% or better. > > > > dwayne > > > > -- > > Dwayne Reid > > Trinity Electronics Systems Ltd Edmonton, AB, CANADA > > (780) 489-3199 voice (780) 487-6397 fax > > www.trinity-electronics.com > > Custom Electronics Design and Manufacturing > > > > -- > > http://www.piclist.com PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > > >-- >http://www.piclist.com PIC/SX FAQ & list archive >View/change your membership options at >http://mailman.mit.edu/mailman/listinfo/piclist --=20 Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .