Could someone recommend a linear regulator for high Vin-Vout application?

[m4l490n]

Hello everybody

I'm recurring to the collective knowledge and experience for my issue. I have to find a linear regulator that can withstand the condition where it has to manage a 12V input to regulate a 5v output @ 1A.

I need it to be linear since there is no space or budget to put a switching regulator and all the passives involved in such regulators and also to avoid the noise that a switching regulator may introduce.

Basically I need a linear regulator that is capable of dissipating all the power that would be generated by such Vin-Vout difference at 1 amp max.

Do you know any ICs for the task?

Regards.

 

[Vbase]

LM7805.
With the heatsink it will be 10 times the size of a switcher.

 

[KlausST]

Hi,

I think there are thousands ... did you ever look for it?

One of the most often used is xx7805

Klaus

 

[crutschow]

You will need the regulator mounted on a heatsink that will dissipate 7W and keep the regulator junction temperature below its maximum rating at the maximum anticipated ambient temperature.

 

[m4l490n]

Hi,

I think there are thousands ... did you ever look for it?

One of the most often used is xx7805

Klaus

That's why I'm asking, I've seen that there are thousands and I ask the community for advice to find a good solution. I barely know the 7805, is it a good quality regulator?

Thanks anyway for answering.

 

[ads-ee]

Due to the size of the heat sink required you're probably going to require more space (and greater cost) than a switcher (module) and the 7805.

The switcher drops the voltage from 12V to say 6V with 90+ efficiency and the linear drops the 6V down to 5V with really poor efficiency, but now the dissipation is a lot less and you won't need a massive heat sink.

 

[m4l490n]

Due to the size of the heat sink required you're probably going to require more space (and greater cost) than a switcher (module) and the 7805.

The switcher drops the voltage from 12V to say 6V with 90+ efficiency and the linear drops the 6V down to 5V with really poor efficiency, but now the dissipation is a lot less and you won't need a massive heat sink.

Yeah that's what I'm fearing. I don't have the space for a massive heatsink. I will have to drop from 12 to 8 or 9 and then to 5 or put a switching regulator.

 

[ads-ee]

Yeah that's what I'm fearing. I don't have the space for a massive heatsink. I will have to drop from 12 to 8 or 9 and then to 5 or put a switching regulator.

If you do that 12 to 8 to 5 using linear regulators, you'll just dissipate more power than a straight 12 to 5 drop. They way most people do this is use a switcher (module) to drop from 12 down to something like 5.5 or 6, then they use the linear to drop from that to 5V. Much much more efficient and space saving, you probably won't even need a heat sink.

- - - Updated - - -

Something like this followed by a 7805. As you can see there aren't that many components outside the switcher.

Don't know if you've look at the prices of heat sinks but they aren't cheap.

 

[m4l490n]

Something like this followed by a 7805. As you can see there aren't that many components outside the switcher.

Don't know if you've look at the prices of heat sinks but they aren't cheap.

Thank you for the suggestion. I think I'll do this. It seems the most cost effective and efficient solution.

Regards

 

[crutschow]

Note that the 7805 needs a 7V minimum input for proper regulation at 5V output.

 

[dick_freebird]

Have you looked into the modules like National (TI) "simple
switcher"? There are ones out there that have everything
internal, aside maybe from the large bulk input and output
caps which you'd need for a linear as well, and the packaging
is not much larger than an IC product (certainly less than a
well heatsinked TO-220). LTC, Intersil, Micrel, all have module
type offerings in IC-like footprints.

 

[ads-ee]

Note that the 7805 needs a 7V minimum input for proper regulation at 5V output.

True using the original, but there are a lot of newer parts that have a much lower dropout voltage e.g. https://www.fairchildsemi.com/datasheets/KA/KA78R05C.pdf just to name one (out of hundreds).

 

[m4l490n]

Have you looked into the modules like National (TI) "simple
switcher"?

Yeah I may use one of those indeed to drop the 12V to 6 and then low-noise fast transient response LDOs to get 5V and 3.3V because definitely I don't have room for any kind of heat sink.

 

[ads-ee]

Interesting that the "simple switcher" seems to require more external components than the Linear part I mentioned in post #8.