[time-nuts] OCXO Soft-Start

jimlux jimlux at earthlink.net
Thu Apr 13 11:15:00 EDT 2017

On 4/13/17 6:17 AM, Bob kb8tq wrote:
> Hi
> It’s a good bet that there is at least one regulator IC inside any modern OCXO.
> As you slowly ramp the input voltage on a regulator, various odd things may
> or may not happen. A 1 mv / s ramp on the outside can be “who knows what”
> at the oscillator level. That said, slow voltage ramps are a really good way to put
> all sorts of oscillator circuits into really odd modes. Clock oscillators (XO’s) and MCU
> built in clock circuits very definitely fall into this category.
> The same sort of “who knows what” problem also gets into the rest of the circuit.
> A limited supply might work fine nine times out of ten or 99 out of 100. On the
> odd time out, something goes poof !
> Bob

This is a known problem with many FPGAs, particularly those which 
configure themselves from on or off-board flash memory.

They have all sorts of little sequencers internally which are driven by 
(very non-time-nuts-quality) oscillators.

And even some non-flash based anti-fuse parts:

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