Appendix E. Power Supply; Power Supplies; Battery-Backup Circuits - Rabbit RabbitCore RCM3400 User Manual

Appendix D provides information on the current requirements
of the RCM3400, and includes some background on the chip
select circuit used in power management.
E.1 Power Supplies
The RCM3400 requires a regulated 2.8 V – 3.45 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 RCM3400 board through header J1.
An RCM3400 with no loading at the outputs operating at 29.4 MHz typically draws 97 mA.
E.1.1 Battery-Backup Circuits
The RCM3400 does not have a battery, but there is provision for a customer-supplied bat-
tery to back up the data SRAM and keep the internal Rabbit 3000 real-time clock running.
Header J2, shown in Figure E-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 RCM3400 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
A
PPENDIX
J2
GND
2
1
33 34
Figure E-1. External Battery Connections
at Header J5
E. P
OWER
External
Battery
VBAT_EXT
S
UPPLY
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