Appendix D. Power Supply; Power Supplies; Battery-Backup Circuits - Rabbit RCM3000 User Manual

D.1 Power Supplies
The RCM3000 requires a regulated 3.3 V ± 0.15 V DC power source. The RabbitCore
design presumes that the voltage regulator is on the user board, and that the power is made
available to the RCM3000 board through header J2.
An RCM3000 with no loading at the outputs operating at 29.4 MHz typically draws 145 mA.
The RCM3000 will consume an additional 10 mA when the programming cable is used to
connect the programming header, J3, to a PC.
D.1.1 Battery-Backup Circuits
The RCM3000 does not have a battery, but there is provision for a customer-supplied bat-
tery to back up SRAM and keep the internal Rabbit 3000 real-time clock running.
Header J2, shown in Figure D-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 3000 real-time clock to retain data with the RCM3000 powered down.
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.
User's Manual
Downloaded from Elcodis.com electronic components distributor
A
PPENDIX
Appendix D provides information on the current requirements
of the RCM3000, and includes some background on the chip
select circuit used in power management.
VRAM
+3.3V
Figure D-1. External Battery Connections
D. P
J2
VBAT_EXT
30
29
GND
31 32
at Header J5
S
OWER UPPLY
External
Battery
103