On Wed, 12 Apr 2017 20:18:38 -0700, you wrote: >On 4/12/17 7:14 PM, Richard (Rick) Karlquist wrote: >> 10.9 MHz is likely the B-mode of the SC cut. >> (It's a different mode, not a different overtone). >> This mode has a tempco of 20 ppm and is used >> to do thermometry. >> >> IMHO, there is NO excuse for the oscillator >> designer to design an oscillator that doesn't >> oscillate unconditionally in the right mode. >> NONE! What was the actual manufacturer of >> the OCXO? (AFAIK, Trimble doesn't make their >> own). >> >> My old boss at Zeta Labs (a really great boss) >> used to walk up to people who were testing >> their latest circuit and momentarily turn >> down the current limit on each of the power >> supplies to see if the circuit recovered >> correctly. It often didn't, and then it >> was back to the drawing board... >> > >These days, a common trap is when you've got a DC/DC converter on the >input - with a soft start, the current goes huge, causing all kinds of >problems. > >(I'm in the middle of closing a failure report on just such a >sensitivity - an unexpected interaction between the source DC/DC >converter and the load DC/DC converter..)
Linear regulators with foldback current limiting and sometimes safe operating area protection can do the same thing with unfriendly loads. Safe operating area protection becomes a problem when the input to output voltage difference is large lowering the current limit at low output voltages. A more insidious problem and design mistake has sometimes occurs with thermal protection. If the thermal protection does not have enough hysteresis, then the regulator cannot "hard start" into a heavy load at high temperature and turns itself into a temperature controlled oven. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.