??? 04/27/07 09:27 Read: times Msg Score: +1 +1 Informative |
#138089 - Let The Microconroller Decide Responding to: ???'s previous message |
I have had good luck applying a circuit like that shown here. The dual N-FETs can be a dual SOT363 type package and the two BAT54's are of course a dual configuration in a SOT23. This circuit lets the Microcontroller decide when to power-down the unit. This can be very important if there are things being stored in a serial EEPROM for example. The MCU can also monitor the push button switch. This can be kept as a power ON switch or a toggle On/Off switch as determined by MCU software.
I show a P-FET pass transistor for switching the power on and off. You may excange this for a voltage regulator that has a low active enable input. Note that having the ability to monitor the push button switch, even if it is not used as a toggle type switch, permits special setup modes in the MCU software that are invoked by monitoring that the user is holding this button and some other switch down at the same time. Michael Karas |