Voltage regulator Tutorial

The question on how to best power the PICAXE comes up often.
As such I decided to write a brief tutorial. With emphasis on "brief".

This is not an all-inclusive treatise on power supplies...that would take several hundred pages. If you require additional info, please google it!

Hi fernando - this is indeed a good start for frequently asked questions - a fast look causes me to ask for one additional comment on LDOs - in general [if not always] they have a higher quiesent and increasing current as the drop voltage lowers as well as the stability problems - and you certainly do have to RTFDS! I hope rev-ed will incorporate more of this material in their manuals since it comes up so often! Thanks for getting the ball rolling...

Thanks for the tutorial. One question that comes up frequently is what LDO regulators are good for battery-powered designs, especially those which need to maintain 5 volts because of ADC or the needs of a particular part. If you have thoughts regarding those for, say, 100mA, 300-500mA, 1A, I'm sure numbers would be interested in viewing.

This is work in progress...the power supply topic is quite extensive, and can be definitively expanded a lot.
You are absolutely correct about the quiescent current increase on LDOs as the dropout is reached.....I gave it a brief though but hesitated whether to include that much detail.

For heatsink calculations, I was writing a short spreadsheet, but found an online calculator (actually, there are many) which is relatively simple and offers some suggestions:

http://www.daycounter.com/Calculators/Heat-Sink-Temperature-Calculator.phtml

LDO & low operating curent

For very low operating current and LDO the LM2936-5.0 is an excellent though somewhat expensive choice... I built a logger in 1992 that had less than 100ua operating current using one of these and a PIC16C71 and LMC6042 op amps. There are a great many LDOs now available for various current ranges - it is important to read the data sheets carefully - some of them claim to be 'no cap' as in capacitor but a lot are finicky. Not so easy to say what's best as new ones appear every week!

I see the Microchip MCP1703 and TC1014, TC1015, TC1185 LDOs look like excellent inexpensive units up to 250ma...

Voltage regulator

fernando_g said:

The question on how to best power the PICAXE comes up often.
As such I decided to write a brief tutorial. With emphasis on "brief".

This is not an all-inclusive treatise on power supplies...that would take several hundred pages. If you require additional info, please google it!

Click to expand...

Thanks for that, very useful!