VULCAN Technical Manual
Power and power management
© 2007 Eurotech Ltd Issue D
37
Power and power management
Power supplies
The VULCAN is designed to operate from a 5V±5% supply (4.75V to +5.25V).
The power connector J9 has a +12V connection defined, but is not required for the
VULCAN under normal operation. It can be used to 12V to the PC/104 stack if
required. For information about the power connector, see
, page
There are three on-board supply voltages derived from the +5V supply. These are
+1.3V (µP core), +2.5V (Ethernet PHY core) and +3.3V.
The reset circuitry mo5V, +1.3V, +3.3V, +2.5V supply rails. If any of them falls
below the threshold, the board is placed in reset. When the power supply rises above
the threshold voltage the board comes out of reset and reboots itself.
Power rail:
+5V +3.3V +2.5V +1.3V
Reset threshold:
4.63V 3.09V 2.34V 1.18V
Battery backup
An external battery (CR2032 or similar) pro2.8V to +3.3V can be used to
backup the DS1302 RTC and the SRAM. The external battery supplies power to the
battery backup circuit only when there is no +5V supply to the board. A battery backup
supervisor circuit is used to enable battery switchover.
To use an external battery, connect its + and - terminals across J9 pins 3 (VBAT) and 2
(GND), respectively. For connector and mating connector details, see
, page
The SRAM minimum supply voltage in data retention mode is 1.5V, and the DS1302
minimum voltage is 2V. Please check the datasheet for external battery details
concerning mAh at 3V and operating temperature.
The user jumper JP2 must not be fitted if an external battery is connected.
GoldCap backup
An on-board super capacitor (GoldCap 0.2F) can be used to backup the DS1302 RTC.
The super capacitor supplies power to the DS1302 RTC only when there is no +5V
supply to the board.
To use the super capacitor, fit the jumper JP2. See
, page
.
The GoldCap maximum voltage is +3.2V when fully charged and the DS1302 minimum
voltage is 2V. The GoldCap provides timekeeping for a maximum of 5 days at room
temperature.