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I was looking for a low quiescent voltage regulator to use in a low power atmega328 device and came across some regulators such as LM2574, LM2575 or MC33761, that has an on/off pin. How does one use that pin?

I'm a bit confused. The only way I could think of controlling this pin would be using the uC, but turning the regulator off wouldn't turn the uC off as well?

Edit: What happens when the regulator is turned off?

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  • \$\begingroup\$ Only if the regulator is powering the uC. \$\endgroup\$ – Ignacio Vazquez-Abrams Oct 18 '13 at 19:50
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Enable/Shutdown pins on voltage regulators are used from externally controlled circuits. Unlike most hobbyist circuits where a single regulator powers everything, more complex circuits might need to control multiple regulators for different purposes.

Even in a single regulator circuit, an on-off pin could be used by a microcontroller on that regulator to reset itself.

And some regulators allow the On/Off pin for rapid toggling. Essentially allowing PWM control of the regulator, for example, for led dimming.

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You use the pin to enable/disable the regulator, saving power. How this is implemented is up to you.

You could have it enable the regulator and power up a microcontroller if - for instance - an audio jack was inserted into the system -- or create a microcontroller that turns itself off but needs external interaction to power back up. The possibilities are many.

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