MTF of PIC + 78L05

Hi guys, I've been reviewing a circuit design which was going to run on dual power supply (power side and MCU control side) and now intend to put the control circuitry which is essentially a pic powered on a 78L05 (or equivalent) on the main supply that is on 24/7.

I'm now going to have the 78L05 reg and associate caps powered off 12 V and the pic off 5 V 24/7, what sort of life expectancy can I be looking at ?. I suppose I'm concerned as I still treat the pic as a computer versus a simple digital chip

The lifetime of all semiconductor devices is normally quite long (years) if the are operated within their ratings. The primary factor is heat, the junction temperature of the device due to ambient temperature (including the temperature rise of any housing it's in) and the power dissipation of the device and how well it is heat sunk. A Google of Semiconductor MTBF found many articles on this. They should be able to provide you more detailed info on the subject.

A microprocessor is basically just a complex digital logic chip. Considering how few failures of these devices occur in PCs, they would seem to have an MTBF comparable to other digital chips.

thanks for the reassurance, yea it should not be getting that hot (I've been designing specifically for low heat) so should all be ok

Even if you built 100 of them you could expect them all to be working long after you are gone.