LDO low drop out voltage regulator?

Using Arduino General Electronics
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I'n new at the Arduino world, but now impossibly hooked... I've assembled several DIY Arduino boards (328 chips) mostly to run LCD's. All will be mostly run from a 9V battery. I have only used the 7805 voltage regulator so far, as instructed at http://www.arduino.cc/en/Main/Standalone

I recently read about the LDO's "advantages" and I'm still pretty unclear. I searched and read lots of posts b4 my question. I kmow WHAT it is, but not sure if I should be using them instead.

Is it "better" to use a LDO VR instead of the regular old 7805? Longer battery life or anything?

I'm still a newbie at this. Thanks!

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Is it "better" to use a LDO VR instead of the regular old 7805? Longer battery life or anything?

What is better then either of those two choices is a switching regulator. They can approach 90% efficiency. If your using a 9vdc battery regulated down to +5vdc, the LDO offers no real advantages over the old 7805. What you should be asking yourself is what should I power my board from other then a 9vdc battery. And the answer is almost any other method would be an improvement. You will waste lots of money buying those wimpy capacity 9vdc batteries.

Lefty

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The advantage of a LDRis you can run it with a lower voltage in. As you want to use a 9V battery there is no difference.

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retrolefty:

Is it "better" to use a LDO VR instead of the regular old 7805? Longer battery life or anything?

And the answer is almost any other method would be an improvement. You will waste lots of money buying those wimpy capacity 9vdc batteries.

Agree completely. In the case of a portable project (like hanging on a wall), I need to use the battery. I will have a switch on it. Others will be hooked to cheapo wall warts.

Thanks! Will look into the switching regs.

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For example, this switching DC-DC converter is a drop-in replacement for linear regulators: DigiKey OKI-78SR and is 90.5% efficient.

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An alternative is to run the AVR at 3.3 to 3.7 V off a LiPo rechargeable battery/cell. No regulolator needed (other than for charging)

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At a high level, a LDO regulator may not really help with power savings, but a certain class of regulator (which usually are LDO) can be very useful. You should look for a regulator with a lower quiescent. I do not have the datasheet for the 7805 handy, but I'm sure it is in the 10mA range. The means, the 7805 regulator requires ~10mA just to operate, even with no load. If your project uses 3mA, your overall load will actually be ~13mA because of the regulator. A 9V cell usually averages ~300-400mAH... an extra 10mA can make a huge impact to battery life.

Check out the MCP1702. It has a quiescent current in the micro-amp range. The only downside is cost, which is ~$0.50 each from Microchip or a supplier like Digikey or Mouser. A boutique like Sparkfun would likely sell them for $5.00.

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Thank you decep for this explanation. I looked at a 7805 datasheet and it says 5-8 mA quiescent (a new term for me). I looked for the MCP1702 - here's Digikey I assume:

Datasheet says 2.0 uA quiescent and it's 52 cents :slight_smile: The 7805 I've been using is .41

Minimizing the draw on the battery is my goal.

I look forward to trying this out! Thanks.

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In certain circumstances, a Low Dropout Regulator can approach or exceed the efficiency of a switching regulator. Since the efficiency of any regulator is a function of the difference between Vin/Vout and the current. If you are driving a high current cree xml led @ 3 amps, the forward voltage is 3.35 volts. If your Vin is a 3.7v Lipo, the efficieny can be very good. The quiescent current in a flashlight is pretty meaningless as well. Other benefits are being less noisy, and fewer components. You can even run LDO regulators in parallel like in this 1 amp led driver.