User Guide

NHB–3
Technical Documentation
PAMS
Desktop Charger CHH–2
Original 26/97 Page 9
Watchdog Circuit
The processor generates positive pulses to output PC7 (pin 18). These pulses
are received by transistor V201 discharging capacitor C161. The capacitor is
charged through resistor R163. This voltage is fed to regulator N100 shutdown
input (pin 3) through transistor V162.The 5V reference supply is generated by
regulator N100.If the processor stops the voltage across the capacitor in-
creases and the regulator is switched off.