Using 2v caps in the place of a 2.5v cap

[spleenharvester]

Hey all.

I haven't really been able to get a clear answer on this - some people have told me it would work and some have told me it would not work.

Basically, I wish to replace a low-ESR 2.5V cap in a CPU Vcore power section (one of those horrid NEC/Tokin OE907) with some low-ESR 2.0V tantalum caps.

I've taken readings and the voltage doesn't rise above 1.2V (well, it powers a CPU, so if it reached 2.0V it would probably die very quickly). And considering many 2.0V caps are used for the same function in similar laptops, surely it would be fine?

My worry is, would the lower max voltage mean it won't last long term? Will it be completely safe to use?

Cheers

[gg1978]

Re: Using 2v caps in the place of a 2.5v cap

It'll be fine with regard to the voltage.. I'm not sure what kind of ESR the NEC/Tokin part has however..

[spleenharvester]

Re: Using 2v caps in the place of a 2.5v cap

Wonderful, cheers man.

900uF 1.5mOhm, using 4x 330uF 6mOhm caps in parallel gives the same 1.5mOhm reading however.

[severach]

Re: Using 2v caps in the place of a 2.5v cap

Get the datasheet on the PWM voltage regulator chip. For example, the highest voltage offered on the ISL6247 is 1.6000v making a 2.0v capacitor safe no matter what processor is installed. If you're certain that no other processor will ever be installed then your 1.2v measurement is valid.

[Th3_uN1Qu3]

Re: Using 2v caps in the place of a 2.5v cap

Yes, it will be just fine. Voltage derating is done so that the parts last longer - but since you are replacing a known problematic Tokin, it's pretty much guaranteed the replacements will last the whole working life left of this laptop, even if they're rated at just 2 volts.

Remember that 16v caps are routinely used for 12v rails and they hardly ever go bad if they're quality ones.