3V Voltage Regulator with Shutdown Feature

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- 30th August 2009, 05:28
rsocor01

3V Voltage Regulator with Shutdown Feature

I bought this nice 3V voltage regulator to use in my PIC projects. It has very low supply voltage and good overall characteristics. But, the feature that I probably like the most is the power saving shutdown mode. If the shutdown pin is high then the regulator is enable, and if this pin is low then the regulator is in shutdown mode.

Now come the questions. The datasheet says that this shutdown pin can be controlled from a microcontroller port. Nice, but then how do you make this port high before there is any power in the circuit for the PIC to come up? Remember the shutdown pin has to be high. And when you make this shutdown pin low, it has to stay low otherwise the regulator won't be in power saving mode. Does anybody know of an easy way to make this work?

Thanks,

Robert
- 30th August 2009, 05:29
rsocor01

Here is the datasheet,

http://ww1.microchip.com/downloads/e...Doc/21335b.pdf
- 30th August 2009, 05:42
mackrackit

Have a momentary switch to manually power the regulator. Hold the switch until the PIC boots.
- 30th August 2009, 05:49
rsocor01

Thanks mackrackit for your idea, but I really want to use this feature to shutdown the circuit if it hasn't been used for a certain amount of time. I want to use it like a "SLEEP" command. This regulator uses a current near zero (0.5 uA max) when in power saving mode, so that would make it ideal for battery operated applications.

Robert,
- 30th August 2009, 05:52
rsocor01

mackrackit,

I'm sure there has to be a way to control this shutdown pin with circuitry without holding a pushbutton. Thanks anyways for your idea.

Robert
- 30th August 2009, 06:04
mackrackit

I misunderstood,
you want the pic or some circuit to start the rgulator?
I was thinking you were just going to have the pic do the shut down.
- 30th August 2009, 06:16
rsocor01

mackrackit,

Well, yes I want the pic to do the shutdown.
- 30th August 2009, 06:22
mackrackit

Quote:

Originally Posted by rsocor01

mackrackit,

Well, yes I want the pic to do the shutdown.

OK then,the suggestion I made before was how to start it.

To have the PIC control it have a PIN with a pull down resistor that is connected to the enable pin of the regulator. Said PIN will always be HIGH until the program makes it low for what ever reason you code it for.
- 30th August 2009, 06:34
rsocor01

mackrackit,

Yeah, but I don't want to start the circuit with a pushbutton. I have already designed my circuit and it does not use a pushbutton to start it. It uses a slide switch and I want to keep it like that for some other design reasons. Anyways, I will keep your idea in mind for future projects.