User’s Manual
93
A
PPENDIX
C. P
OWER
S
UPPLY
Appendix C provides information on the current requirements of the
RCM4510W, and includes some background on the chip select circuit
used in power management.
C.1 Power Supplies
The RCM4510W requires a regulated 3.3 V DC ±5% power source. The RabbitCore design pre-
sumes that the voltage regulator is on the user board, and that the power is made available to the
RCM4510W board through header J1.
An RCM4510W with no loading at the outputs operating at 29.48 MHz typically draws 80 mA,
and may draw up to 150 mA while the XBee RF module is transmitting or receiving.
C.1.1 Battery Backup
The RCM4510W 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 4000 real-time clock running.
Header J1, shown in Figure C-1, allows access to the external battery. This header makes it possi-
ble to connect an external 3 V power supply. This allows the SRAM and the internal Rabbit 4000
real-time clock to retain data with the RCM4510W powered down.
Figure C-1. External Battery Connections
at Header J1
A lithium battery with a nominal voltage of 3 V and a minimum capacity of 165 mA·h is recom-
mended. A lithium battery is strongly recommended because of its nearly constant nominal volt-
age over most of its life.
1
8
2
7
VBAT_EXT
GND
External
Battery
J1
+3.3 V_IN
