20-101-0497 Rabbit Semiconductor, 20-101-0497 Datasheet - Page 64

• Manufacturer Part Number: 20-101-0497
• Description: MODULE OP6810 W/O ETH/MEM EXPANS
• Manufacturer: Rabbit Semiconductor

Specifications of 20-101-0497

• Module/board Type: Single Board Computer Module
• Product: Prototyping Accessories
• Processor Type: Rabbit 2000
• Sram: 128 KB
• Flash: 256 KB
• Timers: 8 bit, 10 bit
• Number Of I/os: 24
• Operating Voltage: 9 V to 36 V
• Power Consumption: 1.5 W
• Board Size: 111 mm x 91 mm x 33 mm
• For Use With/related Products: OP6810
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 20-101-497; 20-101-497

B.2 Batteries and External Battery Connections
The SRAM and the real-time clock have provision for battery backup. Power to the SRAM
and the real-time clock (VRAM) is provided by two different sources, depending on whether
the main part of the OP6800 is powered or not. When the OP6800 is powered normally, and
Vcc is within operating limits, the SRAM and the real-time clock are powered from Vcc. If
power to the board is lost or falls below 4.63 V, the VRAM and real-time clock power must
come from a backup battery in your system which you would connect to pin 40 of header J1
on the OP6800 via the ribbon cable. The backup battery should be able to supply 2.85 V–
3.15 V at 10 µA.
The reset generator circuit controls the source of power by way of its
B.2.1 Battery-Backup Circuit
Figure B-1 shows the battery-backup circuit located on the OP6800 module.
The battery-backup circuit serves three purposes:
• It reduces the battery voltage to the SRAM and to the real-time clock, thereby limiting
• It ensures that current can flow only out of the battery to prevent charging the battery.
• A voltage, VOSC, is supplied to U6, which keeps the 32.768 kHz oscillator working
VRAM and Vcc are nearly equal (<100 mV, typically 10 mV) when power is supplied to
the OP6800.
60
the current consumed by the real-time clock and lengthening the battery life.
when the voltage begins to drop.
Figure B-1. OP6800 Backup Battery Circuit
T
W
W
thermistor
W
W
W
/RESET
W
MiniCom (OP6800)
output signal.