User`s manual

42 RabbitCore 2000
C.1 Power Supplies
The RabbitCore 2000 requires a regulated 5 V ± 0.25 V DC power source.
A RabbitCore 2000 with no loading at the outputs operating at 18.432 MHz typically
draws 98 mA, and a RabbitCore 2000 operating at 25.8048 MHz typically draws 130 mA.
The RabbitCore 2000 will consume 13 mA to 15 mA of additional current when the pro-
gramming cable is used to connect J3 to a PC.
C.1.1 Batteries and External Battery Connections
The RabbitCore 2000 does not have a battery, but there is provision for a customer-sup-
plied battery to back up SRAM and keep the internal Rabbit 2000 real-time clock running.
Header J2, shown in Figure C-1, allows access to the external battery. This header makes
it possible to connect an external 3 V power supply. This allows the SRAM and the inter-
nal Rabbit 2000 real-time clock to retain data with the RabbitCore 2000 powered down.
Figure C-1. External Battery Connections at Header J2
A lithium battery with a nominal voltage of 3 V and a minimum capacity of 165 mA·h is
recommended. A lithium battery is strongly recommended because of its nearly constant
nominal voltage over most of its life.
The drain on the battery by the RabbitCore 2000 is typically 16 µA when no other power is
supplied. If a 950 mA·h battery is used, the battery can last more than 6 years:
The actual life in your application will depend on the current drawn by components not on
the RabbitCore 2000 and the storage capacity of the battery. Note that the shelf life of a
lithium battery is ultimately 10 years.
VCC
VRAM
31
34
32
33
GND
VBAT
External
Battery
950 mA·h
16 µA
------------------------
6.8 years.=