User’s Manual
99
APPENDIX C. POWER SUPPLY
Appendix C provides information on the current requirements of
the RCM4100 series of modules, and includes some background
on the chip select circuit used in power management.
C.1 Power Supplies
The RCM4100 series of modules requires a regulated 3.0 V – 3.6 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 RCM4100 series of modules through header J2.
A module with no loading at the outputs operating at 58.98 MHz typically draws up to
125 mA.
C.1.1 Battery Backup
The RCM4100 series of modules do not have a battery, but there is provision for a cus-
tomer-supplied battery to back up the data SRAM and keep the internal Rabbit 4000 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 4000 real-time clock to retain data with the module 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 mAh is
recommended. A lithium battery is strongly recommended because of its nearly constant
nominal voltage over most of its life.
1
8
2
7
VBAT_EXT
GND
External
Battery
J2
+3.3 V_IN