I was originally considering using a 10 µF 6.3 V 0603 ceramic capacitor for stabilising the onboard voltage regulator on my microcontrollers. However, it may not be capable because of temperature coefficients, tolerances and applied voltage (losing up to 60% of the rating). Therefore, I am considering moving to using tantalum capacitors.
The microcontroller LDOs output 2.25 V - 2.75 V for powering the internal core. I am using a PIC24FJ64GA004 and dsPIC33FJ128GP804. Would it be fine to use a 4 V capacitor here? I have always used 2-3x rating for electrolytic capacitors, but maybe the same problems with aluminum electrolytic capacitors as for tantalum capacitors do not apply (with lifetime decreasing over applied voltage considerably.)
Ideally I'd like to reach a 50,000-100,000 hr MTTF. If tantalum capacitors aren't an option I'm considering using a 22 µF 6.3 V 0805 ceramic capacitor in place (I might have to resize the footprint), because even with a loss of 60% it stays within the minimum requirement of 4.7 µF. Any tips? Has anyone used tantalum capacitors before? What about ceramic capacitors for microcontroller LDOs?
Answer
It depends heavily on the temperature you expect in your application. Recommendations say that 80 % of the rated voltage should never be exceeded, and at 85 °C, you should not apply more than 50 % of the rated voltage. The catalog in this link, for example, has many derating diagrams for various types of tantalum capacitors.
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