Capacitor charge control circuit and microcomputer using the same

摘要

A microcomputer has a CPU, a charge and discharge control circuit connected to the CPU, an input/output port, and comparator. A capacitor is connected to the microcomputer through the input/output port. The comparator outputs a high level signal or a low level signal based on a voltage of the capacitor to the CPU. The charge and discharge control circuit is composed of a totem pole structure having a high side and a low side n-channel type MOSFETs whose common drain terminal serves as an output terminal of the circuit. The high side MOSFET charges the capacitor, and the low side MOSFET discharges the capacitor based on signals from the CPU through the input/output port. The high side MOSFET does not have a parasitic diode whose anode is connected to a power supply and cathode is connected to the common drain terminal.