User’s Manual
81
APPENDIX C. POWER SUPPLY
Appendix C provides information on the current and power sup-
ply requirements of the RCM2100, and some background on the
chip select and battery-backup circuits used in power mange-
ment.
C.1 Power Supplies
The RCM2100 requires a regulated 5 V ± 0.25 V DC power source. The RCM2100 design
presumes that the voltage regulator is on the user board, and that the power is made avail-
able to the RCM2100 board through headers J1 and J2.
An RCM2100 with no loading at the outputs operating at 22.1 MHz typically draws
140 mA. The RCM2100 will consume 13 mA to 15 mA of additional current when the
programming cable is used to connect J5 to a PC.
C.1.1 Batteries and External Battery Connections
The RCM2100 does not have a battery, but there is provision for a customer-supplied bat-
tery 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 RCM2100 powered down.
Figure C-1. External Battery Connections
at Header J2
VCC
VRAM
26
29
27
28
GND
VBAT
External
Battery