Service manual

3.18 TP0332/2
TRICKLE CHARGER
The trickle charger uses a positive input on the RxD pin of the smart interface to power a current
limited source feeding the battery, limiting the current to approximately 130mA. The charger is enabled by
the thermistor in the battery pack, so it is inhibited if a battery pack is not fitted (this is necessary to prevent
a voltage at the battery connector which could damage the radio when no battery is present).
The charger can also be inhibited by the processor to permit an RS232 (or IIC) device to drive the
RxD input correctly. This is achieved using the processor pin driving the green LED.
BATTERY CONNECTIONS
Battery Connections to Radio
The battery connections are three spring loaded pins mounted on the radio PCB. These pins
protrude through the metal casting to make contact with contact pads on the battery. The function of these
pads on the battery are listed in Table 3.7.
Table 3.7 Battery Connections to Radio
Battery Connections to Charger
These connections are located on the base of the battery.
Table 3.8 Battery Connections to Charger
Signal Name Use Signal Type Direction
+VE Battery Positive Terminal 5V to 11V (during fast
charge)
To radio (from radio
during charge)
–VE Battery Negative Terminal Radio Ground To radio
TEMP To disable fast charging when
pulled low.
Open drain, active low From radio
Signal Name Use Signal Type Direction
+VE Current limiting in reverse
direction to prevent excessive
discharge
9V to 11V From Charger
–VE Battery Negative Terminal 0V From Charger
TEMP Voltage which decreases with an
increase in cell temperature.
0 to +5V To Charger
BAT_TYPE Battery type resistor 47k Resistor to –VE To Charger