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 3 volt "cutoff" circuit

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wormsmith Posted - Sep 28 2009 : 11:03:36 AM
I need a 3Volt power "cutoff" circuit.

I have a 2.5 - 7 volt power input to a device but in testing the device on a bench top power supply it starts to freak out at about 2.7 volts. So I am looking for a circuit design that would completely disconnect the power to the device if the voltage drops below 3 volts and reconnect the power to the device if the voltage goes back above 3 volts. Also it has to be tiny and light for my application. Any help would be greatly appreciated.
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audioguru Posted - Sep 28 2009 : 5:18:33 PM
An LM10 can be the sensor and a little 2N4401 transistor or 2N4403 transistor can do the switching.
wormsmith Posted - Sep 28 2009 : 1:10:31 PM
The max current load is 75ma at 3 volts DC
codingplanet Posted - Sep 28 2009 : 12:45:09 PM
If your circuit uses a PIC MCU then you may want to look into the brown out detection which is built in. Atmel or other MCUs may also have a similar feature.
audioguru Posted - Sep 28 2009 : 12:22:27 PM
A circuit that applies and cuts off power to a load must have a maximum current rating.
You forgot to say how much current the load uses.

A comparator or opamp can be used as the 3V sensor. A voltage reference is also needed. An LM10 opamp/adjustable voltage reference works from a supply as low as 1.1V and can be the sensor. If the load current is more than 20mA then the LM10 can drive a power transistor to do the switching.

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