3v3 PSU design - Electronic Circuits Projects Diagrams Free

mikesmixes777 · 25th March 2008, 12:15 PM

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** · 25th March 2008, 12:19 PM

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 · 25th March 2008, 12:23 PM

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 · 25th March 2008, 12:32 PM

half an amp! really?

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

Mark

mikesmixes777 · 25th March 2008, 12:46 PM

Quote:

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 · 25th March 2008, 01:05 PM

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 · 26th March 2008, 11:06 AM

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.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Latest
PSU Design	yngndrw	Electronic Projects Design/Ideas/Reviews	3	25th March 2008 04:24 PM
MP Lab Program Help	bamafan54	Micro Controllers	3	19th October 2007 02:53 AM
help understanding this hbridge design....	jaydag71	Electronic Projects Design/Ideas/Reviews	2	5th June 2007 10:37 PM
Texas Instruments New Design Center.	chemelec	General Electronics Chat	0	18th May 2006 10:33 PM
anybody knows how to design a calculator???	eleanor	Electronic Projects Design/Ideas/Reviews	4	12th August 2005 05:44 PM

25th March 2008, 12:15 PM	(permalink)
mikesmixes777	3v3 PSU design 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 __________________ "//Some day we'll look back and Laugh"

25th March 2008, 12:19 PM	(permalink)
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?. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

25th March 2008, 12:23 PM	(permalink)
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... __________________ "//Some day we'll look back and Laugh"

25th March 2008, 12:32 PM	(permalink)
UTMonkey	half an amp! really? The only reason I ask is because I will eventually be doing some ethernet projects. Mark

25th March 2008, 01:05 PM	(permalink)
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 __________________ What is a joule per second?

26th March 2008, 11:06 AM	(permalink)
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. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez