7805 operation outside operating temperature

Thread Starter

Travm

Joined Aug 16, 2016
266
I have a small number of 7805 voltage regulators in to220. Data sheet puts operating temperature at 0to85c. Want to use one to power a heated mirror timer in my truck, would often be run considerably below 0.
I don't think it's a big deal, circuit would be fused, and simple enough if it dies I can just order better parts and do it over.
Is this likely to work, and what's the worst that could happen?
 

narkeleptk

Joined Mar 11, 2019
375
Doubt you'll have much issue's with it, 7805 seems good enough for many simple auto applications. You could get all technical for it and I am sure members will but.. meh...
 

Thread Starter

Travm

Joined Aug 16, 2016
266
I can buy 7805s with an operating range of -40 to +85, but just happens I already have a bunch, but I bought them not thinking about running them cold.
Even if they have a shorter life, i can cross that bridge when I get there
 

MrChips

Joined Oct 2, 2009
19,382
Presumably there will be some voltage across the regulator and power being dissipated. That would provide some self heating.

In any case, just get the extended temperature range part and save the others for another project.
 

Thread Starter

Travm

Joined Aug 16, 2016
266
I am considering that. It's just that I already have everything I need, except that extended temp part
 

Kjeldgaard

Joined Apr 7, 2016
379
For that application, I will have no qualms using a 0 to 85 °C voltage regulator.

In the "deep freezer" at worst, I think the output voltage may be 50 mV further away from the nominal value.
 

DickCappels

Joined Aug 21, 2008
5,936
When semiconductors get cold they don't work as well. Your voltage may be off, the regulation might not be as good, but if the work, you probably aren't shortening their lives. Go for it.
 

crutschow

Joined Mar 14, 2008
23,500
It may go some outside its spec voltage limits below 0°C but that's unlikely to be a problem in your application.

As suggested you could test the circuit in your freezer.
 
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