101-1028 Rabbit Semiconductor, 101-1028 Datasheet - Page 164

• Manufacturer Part Number: 101-1028
• Description: MODULE RABBITCORE RCM3750
• Manufacturer: Rabbit Semiconductor

Specifications of 101-1028

• Module/board Type: MPU Core Module
• For Use With/related Products: RCM3750
• Lead Free Status / RoHS Status: Vendor undefined / Vendor undefined

D.1.2 Battery-Backup Circuits
The RCM3750 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 J1, shown in Figure D-1, allows access to the external battery for the RCM3750.
This header makes it possible to connect an external 3 V backup battery. This allows the
SRAM and the internal Rabbit 3000 real-time clock to retain data with the RCM3750
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.
The drain on the battery by the RCM3750 is typically 6 µA when no other power is sup-
plied. If a 235 mA·h battery is used, the battery can last about 4.5 years:
The actual life in your application will depend on the current drawn by components not on
the RCM3750 and the storage capacity of the battery. The RCM3750 does not drain the
battery while it is powered up normally.
Cycle the main power off/on on the RCM3750 after you install a backup battery for the
first time, and whenever you replace the battery. This step will minimize the current drawn
by the real-time clock oscillator circuit from the backup battery should the RCM3750
experience a loss of main power.
D.1.3 Reset Generator
The RCM3750 uses a reset generator to reset the Rabbit 3000 microprocessor when the volt-
age drops below the voltage necessary for reliable operation. The reset occurs between
2.85 V and 3.00 V, typically 2.93 V.
The RCM3750 has a reset pin, pin 36 on header J1. This pin provides access to the reset
output from the reset generator, and is also connected to the reset input of the Rabbit 3000
to allow you to reset the microprocessor externally. R21 protects the reset generator from
being overdriven. This allows the same pin (pin 36 on header J1) to be used to either sense
a reset or to force a reset.
158
NOTE: Remember to cycle the main power off/on any time the RCM3750 is removed
235 mA·h
----------------------- -
from the Protoyping Board or motherboard since that is where the backup battery
would be located.
6 µA
=
4.5 years.
RabbitCore RCM3750