101-0558 Rabbit Semiconductor, 101-0558 Datasheet - Page 87

• Manufacturer Part Number: 101-0558
• Description: COMPUTER SNG BD BL1800 512K SRAM
• Manufacturer: Rabbit Semiconductor

Specifications of 101-0558

• Module/board Type: Single Board Computer Module
• For Use With/related Products: BL1800
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

C.2.1 Battery Backup Circuit
Figure C-5 shows the Jackrabbit battery backup circuitry.
Resistor R12, shown in Figure C-5, is typically not stuffed on the Jackrabbit board.
VRAM and Vcc are equal when power is supplied to the Jackrabbit. R13 prevents any cat-
astrophic failure of Q1 from allowing unlimited current to enter the soldered-in battery.
Resistors R14 and R15 make up a voltage divider between the battery voltage and the tem-
perature-compensation voltage at the anode of diode D80. This voltage divider biases the
base of Q1 to about 2.6 V. V
These voltages vary with temperature. VRAM varies the least because temperature-com-
pensation diodes D80–D82 will offset the variation with temperature of Q1 V
R82 may be stuffed instead of the corresponding D80–D82 to provide the optimum tem-
perature compensation.
Resistor R10 provides a minimum load to the regulator circuit.
User’s Manual
Figure C-5. Jackrabbit Battery Backup Circuit
BE
on Q1 is about 0.55 V. Therefore, VRAM is about 2.05 V.
W
W
W
W
W
W
BE
. R80–
83