Basic Voltage Regulators

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Revision as of 19:44, 5 February 2006 by Wiml (talk | contribs) (category)
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Main-LM1117.jpg
Main-LM317.jpg
Main-LM7805.jpg

Description:
These various voltage regulators.

  • LM1117 is a SMD adjustable regulator
  • LM317 is a PTH adjustable regulator
  • LM7805 is a 5V regulator
  • LM7833 is a 3.3V regulator

These larger regulators usually have a fairly large drop out voltage of 1.5V to 2.5V. This means you need at least 1.5-2.5V above whatever voltage you want out (you'll need at least 7V in to get 5V out for example).

These regulators can be a little noisy. They are cheap and mass produced so don't be surprised if you see 200-500mV of noise on your VCC line. Is this bad? YES. But for most bread boarding applications, this is just fine.

For the 7805 and 7833, just give it an input and you'll get an output. Datasheets will recommend 10-100uF decoupling on both the input and output (always a good thing to do).

The nice thing about the PTH (plated through hole) regulators, you can insert them directly into a bread board and you can heat sink these babies with nice TO-220 bolt-on type heat sink. With a heat sink, you can easily run 1A to 1.5A through these without long-term degredation.

Documents:
The datasheets vary by vendor but most are similar if not identical. The 7805 and 7833 are what I call IGO regulators, because the pinouts are Input-Ground-Output when you are looking at the front.

LM7805 Datasheet - Good for the LM7833 as well.

The LM317 and LM1117 are AOI regulators for the pins are Adjustment-Output-Input. Don't be afraid of using the variable regulators. Get a bag of 240Ohm resistors and then a handful of other values and you will be able to output 5V, 3.3V, and a range of other voltages with just a calculator and a resistor swap. Checkout the [LM317 calculator] for more information.

LM317 Datasheet

Footprints:
SFE Footprint Library

FP Name: TO-220, TO-220 - ADJ, TO-220-Sinked, etc

Manufacturer Info:
There are many mfgs for these basic v-regs.

Supplier Info:
There are a whole range on Digikey and can range from ~0.50 to over $5 depending on the specs! Feel free to list prices and specs of the ones you discover and like to use.

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