マイコンで電源制御

DPがSTのアプリケーションノートの smart on/off controller and voltage monitoring chip from STMicroelectronics. を紹介している
R1,R2,R3,R4の計算式も載っているのが親切

These devices allow easy and safe control of applications run with one or two push-buttons by securely starting or powering down a system and also resetting the processor or disabling power in case of a non-responding application (e.g. code in a dead loop). This makes the STM660x devices suitable for a broad spectrum of applications such as terminals, audio and video players, smartphones, PDAs, PCs, or any portable device.