Digi JACKRABBIT BL1800 - Manual (Page 86)

82 Jackrabbit (BL1800)
C.2 Batteries and External Battery Connections
The soldered-in 950 mA·h lithium coin cell provides power to the real-time clock and
SRAM when external power is removed from the circuit. This allows the Jackrabbit to
continue to keep track of time and preserves the SRAM memory contents.
The drain on the battery is typically less than 20 µA when there is no external power
applied. The battery can last more than 5 years:
The drain on the battery is typically less than 4 µA when there external power is applied.
The battery can last for its full shelf life:
Since the shelf life of the battery is 10 years, the battery can last for its full shelf life when
external power is applied to the Jackrabbit.
Header J2, shown in Figure C-4, allows external access to the battery. This header makes
it possible to connect an external 3 V power supply while replacing the soldered-in 3 V
lithium coin-type battery. This allows the Jackrabbit SRAM and real-time clock to retain
data while the battery is being replaced.
Figure C-4. External Battery Connections at Header J2
Alternatively, header J2 can be used to accommodate an external battery. In this case, be
sure to cut out the soldered-in battery on the Jackrabbit to prevent discharging the external
battery into a dead battery.
950 mA·h
20 µA
------------------------ 5.4 years. =
950 mA·h
4 µA
------------------------ 27 years (shelf life = 10 years). =
EXT BA
TT
J2
1
2
3
4
100 W
R1
VBAT