Appendix D. Power Supply; Power Supplies; Battery Backup - Rabbit RCM3365 User Manual

Appendix D provides information on the current requirements of
the RCM3365/RCM3375 modules, and includes some background
on the reset generator.
D.1 Power Supplies
Power is supplied from the motherboard to which the RCM3365/RCM3375 is connected
via header J4. The RCM3365/RCM3375 require a regulated 3.15 V to 3.45 V DC power
source. An RCM3365/RCM3375 with no loading at the outputs operating at 44.2 MHz
typically draws 250 mA.
D.1.1 Battery Backup
The RCM3365/RCM3375 does not have a battery, but there is provision for a customer-
supplied battery to back up the data SRAM and keep the internal Rabbit 3000 real-time
clock running.
NOTE: A backup battery is highly recommended to back up the data SRAM when using
an RCM3365 with Dynamic C RabbitSys to keep RabbitSys from reverting to its
default settings in case of a power failure.
Header J4, 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 RCM3365/RCM3375 powered
down.
User's Manual
A
PPENDIX
J4
VRAM
30
29
+3.3 VIN
31
32
Figure D-1. External Battery Connections
at Header J4
D. P
OWER
External
Battery
VBAT_EXT
GND
S
UPPLY
133