User`s manual

OEM User’s Manual 119

The actual life in your application will depend on the current drawn by components not on

the RCM5600W and on the storage capacity of the battery. The RCM5600W does not drain

the battery while it is powered up normally.

Cycle the main power off/on on the RCM5600W after you install a backup battery for the

first time, and whenever you replace the battery. This step will minimize the current drawn

by the real-time clock oscillator circuit from the backup battery should the RCM5600W

experience a loss of main power.

NOTE: Remember to cycle the main power off/on any time the RCM5600W is removed

from the Interface Board or motherboard since that is where the backup battery would

be located.

Rabbit’s Technical Note TN235, External 32.768 kHz Oscillator Circuits, provides addi-

tional information about the current draw by the real-time clock oscillator circuit.

F.1.2 Battery-Backup Circuit

Figure F-2 shows a suggested battery-backup circuit.

Figure F-2. RCM5600W Backup Battery Circuit

The battery-backup circuit serves the following purposes:

• It reduces the battery voltage to real-time clock, thereby limiting the current consumed

by the real-time clock and lengthening the battery life.

• It ensures that current can flow only out of the battery to prevent charging the battery.

• Switches to battery power only when the +3.3 V system power supply is off.

F.1.3 Reset Generator

The RCM5600W uses a reset generator to reset the Rabbit 5000 microprocessor when the

voltage drops below the voltage necessary for reliable operation. The reset occurs between

2.85 V and 3.00 V, typically 2.93 V. The RCM5600W has a reset output on the edge

connector.

VBATIO

47 kW

R12

VBAT-EXT

External Battery

+3.3 V

2,2 nF

FDV302P

RESOUT