3v3 PSU design

[mikesmixes777]

Hi,

Any suggestions, I need to get 3.3Vdc from a 12-24Vdc source for my PIC board.

I am currently using a LV1086-3v3 LDO device which is good for up to 1.5A. The problem is that it gets very hot as you increase the input voltage(obviously do to the voltdrop)

I need to connect anything from 5-24Vdc to my board. Any suggestions on how to achieve this.

Many thanks
Michael

 

[Nigel Goodwin]

A large heatsink, or use a switch-mode regulator. PIC's take hardly any current, so it's not the PIC making things hot, but what it's controlling - is it possible to move those before the regulator?.

 

[mikesmixes777]

Thanks Nigel,

I am using the PIC with an ENC28J60 ethernet controller. There is a continuous current draw of around 500mA due to the ethernet controller.

I will prob look at using a switch mode ic. What are available as far as these go? Trying to keep the design as small as possible...

 

[UTMonkey]

half an amp! really?

The only reason I ask is because I will eventually be doing some ethernet projects.

Mark

 

[mikesmixes777]

half an amp! really?

Well around there... The ethernet controller uses max 180mA during tx/rx.

I got a few other devices too, opamps, rs232, eeproms, led's...they all add up eventually...

 

[erosennin]

Hmmm, you could use an LM317 as that supports upto 40V input - you'd need a current bypass as it's a 1A device. This will also get hot too I guess, like Nigel said, you could heatsink it.
Is your device getting to the point where it's shutting itself down? If not, you don't have anything to worry about... It still works =P

 

[Hero999]

An LM317 won't make any difference, it's still a linear regulator and therefore, still burns the extra power as heat.

Use a switching regulator, there are plenty of suppliers, National Semiconductor, Linear Technology, Maxim Semiconductor, etc.