User Guide

NHB–3
Technical Documentation
PAMS
HF Desktop Charger CHH–8P
Original 26/97 Page 13
Functional Description
The DC3 module electronics consists of the following functional blocks:
– Supply voltages
– Control logic
– Battery charging
– Spare battery discharging
– Watchdog circuit
– Microphone amplifier and corresponding switches
– Speaker amplifier and corresponding switches
Supply Voltages
The supply voltage +VI (11.0 V– 20.0 V) for the DC3– and DC4–modules is
taken from the power supply connector X100 connected to the Power Supply
ACS–6.
The battery charging voltage +VCC (10.0 V – 13.0 V) is connected to the phone
or to the spare battery.
+VE voltage (5.0 V) is generated by the regulator N150 to charge totally empty
battery to the +5.0 V level.
+VA voltage (10.0 V) is the supply for the analog parts. From that voltage are
generated also analog voltages +VAN (5.0 V) and +VAS (10.0 V). Reference
voltage +VREF (2.75 V) for the analog is made by the N430–A from the +VAN
voltage.
+5V voltage is the supply for digital parts, generated by the regulator N103.
Control Logic
The phone battery and spare battery charging indication, spare battery
charging and discharging, audio connections and activation of voice mail are
controlled by processor D300. It is a single–chip type controller incorporating
RAM, ROM, A/D converter and a multifunction timer/counter.
The processor communicates with the handphone via the M2BUS. The M2BUS
interface comprises transistors V200, V201 and corresponding resistors.