HP-71B 4Kb (CMT32k FrontPort) Memory Module "Battery" - FRAM

[Garth Wilson]

(01-23-2021 01:00 AM)cruff Wrote:  

(01-22-2021 08:24 PM)Garth Wilson Wrote:  Note that the piezoelectric effect on MLCCs is huge, and the capacitance drops off rapidly above approximately 20% of the WVDC. The dielectric type has an effect too, Y5V being considerably worse than X7R. A Y5V will lose over 85% of its capacitance at its WVDC, whereas the X7R only loses 70%.

Surely at the working voltage, the capacitors have their rated values, within their stated tolerance?

Nope. Their rated values start falling off at 20% of their rated voltage. This is for MLCCs. It does not apply to other types like aluminum electrolytic. Would it be ok to post scans of the EDN article here?