I am having a pretty strange problem that I am unable to solve. Basically, I am using an L7805CV and it is outputting at 5.8V instead of the specified voltage range in the data sheet. At first I was using it in a digital isolation scheme, but when I was unable to solve the problem I took it out and breadboarded it by itself. I am using the caps specified in the data sheet, .33uF and .1uF
Things I have thought/tried:
- Maybe something is iffy with the voltage supply. I've tried 19V and 12V supplies, each providing the same result.
- Maybe the regulator is just faulty. I tried three different L7805CVs, all of them having the same result, albeit slightly different output voltages.
- Maybe the circuit isn't under enough load. I tried 1k and 100 ohm resistors and it didn't change the end result. With no load it still gives the same result.
- Maybe the caps are non-ceramic. They are ceramic.
- Maybe the caps are bad. I have a voltmeter with support for capacitor testing so I checked each of them and they were each within range.
Things you might be thinking:
- Maybe it's the breadboard. Yeah, well, it isn't. At the very least I believe it isn't. I had the original one in a PCB and it was behaving the exact same way.
- Maybe you're an idiot. Yeah, well, yeah.
The power supplies I'm using are a 12VDC switching supply, and a 19VDC Acer computer charger I cut the end off of.
For a relevant circuit diagram check the application circuit for the L7805 which I'm sure most people here are familiar with.
After failing with the L7805 I threw in another regulator I had on hand (I can't remember the number but it's 5V) and it worked fine. A pristine 5.17V, well within range of the data sheet.
Using a 1N4148 diode I can drop the voltage within spec on the L7805, but that is, of course, cheating.