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Chapter 3
Power Interface (J10)
The LittleBoard 550 uses five separate voltages on the board, but only one of the voltages is provided
externally (+5 volts) through the external connector, which uses a 7-pin vertical header with 0.156"
(3.96mm) spacing. Holes for a right angle mounting header are also available at J10. All the onboard
voltages are derived from the externally supplied +5 volts DC +/- 5%. The onboard voltages provide the
CPU core voltages as well as other voltages used on the board.
Table 3-27 gives the pin outs and signals for Power supply connector (J10).
Table 3-27. Power Interface Pin/Signal Descriptions (J10)
Pin #
Signal
1
+5V
2
GND
3
GND
4
+12V
5
+3.3V
6
GND
7
+5V
Notes: The shaded area denotes power or ground. The +12Vand +3.3V on the Power Interface
connector (J10) are used for the PCI and ISA bus power and must be supplied externally. The -5V
and –12V are supplied from an external power supply through the Utility 1 connector (J16).
Power Monitor
Power supply monitoring is performed by the precision triple supply monitor, LTC 1326. This chip
monitors the system voltages and provides an auto-reset or external push button reset capability. The
LTC 1326 monitors three separate voltages Vcore, +5V, and +3.3V. If any of these voltages drop below
–10% of the nominal voltage, the POWER GOOD output is driven low causing a system reset.
CPU Fan
Table 3-28. CPU Fan (J2)
Pin #
Signal
1
GND
2
+5
3
TAG
Note: The shaded area denotes power or ground.
LittleBoard 550
Description
+5.0 volts DC +/- 5%
Ground
Ground
This +12V is are for BUS power only (optional)
This +3.3V is for BUS power only (optional)
Ground
+5.0 volts DC +/- 5%
Description
Ground
+5.0 volts DC +/- 5%
Fan Speed Tachometer
Reference Manual
Hardware
61
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