The ESR of wet aluminum electrolytics skyrockets below 0C. Using them is a good way to build a temperature-activated oscillator.
Polymer alums are good over temperature, but their ESR may be too low for some regulators. Tantalums are just right for 1117 type regs.
-- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
They'll be better off than the regs -- 100C-ish cutoff, and that's Tj on top of whatever power they're dissipating, so I hope this thing isn't actually needing an ampere of capacity and/or an ambient over 60C.
Tim
-- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com
like that low ohmic resistor R for debugging and measuring current too, but as i understand the R is after the cap, so the mlcc problem for LDOs still exists.
I like to put a current measure R between the cap and the feedback voltage divider, so the V drop is regulated out. Disconnecting the load for debugging is done by putting the feedback divider on another pad connected directly on the cap output, additionally put on the layout.
MIKE
-- www.oho-elektronik.de OHO-Elektronik Michael Randelzhofer FPGA und CPLD Mini Module
No, the resistor goes between the regulator and the cap, but the voltage divider is on the regulator side. Otherwise the output voltage would go nuts.
Cheers
Phil Hobbs
That does sound an awful lot like what happens with LDO's - there is a range of output cap that will oscillate. Never heard of it for a 317 though. A re-spin or an LDO in drag?
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