[time-nuts] IFCS 2020 tutorial - low noise electronics for time/frequency metrology

[Magnus Danielson]

On 2020-07-22 03:39, Richard (Rick) Karlquist wrote:
>
>
> On 7/21/2020 4:27 PM, Magnus Danielson wrote:
>
>>
>> In capacitors, two things make them microphonic, voltage over the
>> capacitor and the high-dielectric constant as this makes it more
>> sensitive to mechanical stress, and this also tends to make them very
>> sentistive to thermal stress. So X7R is terrible for instance.
>>
>
> The LT3042/LT3045 data sheets should be of interest in this regard.
> ADI calls out a particular Murata capacitor that supposedly has low
> microphonics.  However, I believe its tempco is X7R, so I can't
> reconcile that with what you said.  It does lose less capacitance
> at higher voltages than any other capacitor with a value of 10 uF
> that I have seen, so from what you are saying, this should give
> it lower microphonics.
I was noting a general tendence, but there can be exceptions from the
rule naturally.
>
> Unfortunately, this technology appears to have been orphaned by
> Murata, receiving the dreaded NRND notation.  It appears that
> it will be available in distribution for the immediate future
> at least.

Another problem, it can be hard to depend on too exotic components, as
they can be end of life before your design is, if you are too dependent
on them, large redesign or end of life remains the options.

Cheers,
Magnus