RCH
INSTALLATION AND MAINTENANCE MANUAL model TOUCH ME
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9.12 RAM, RTC and CPU MEMORY BACKUP CIRCUIT
When the device is fed normally, output voltage of the circuit (M3) is about 5,8V; this voltage
goes through the diodes D2 and D3 with output being respec5V for all logical
circuits, and VB which feeds the charging circuit of the buffer battery, Power Supply the
integrated SRAM memory and RTC clock circuits through the diode D7 (+VB).
In particular, the VB voltage is backed-up by a rechargeable battery VL2330 (BT1) which
has the function of keeping date in the SRAM and RTC in case of no power supply (if the
device is turned off).
Without power supply (switch is OFF), +VB voltage is supplied to the RAM and the
microprocessor thanks to a rechargeable BT1 battery; in this case, the VB voltage rating is
about +3V.
The circuit is protected from current overloads by the resistor R55. R54 is the limiter
of the
buffer battery.
The battery used is a rechargeable lithium battery. Voltage rating is 3V and capacity is
30mAH.
WARNING:
Exhausted batteries must be disposed of by technical service personnel, according
to the norms regarding rechargeable lithium batteries.
