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26 CMX158886 cpuModule BDM-610000049 Rev G
Auxiliary Power (CN3)
The Auxiliary Power connector (CN3) can be used to supply power to devices that are attached to the
cpuModule. These devices include hard drive, front-end boards for data acquisition systems, and other devices.
Power can also be conveyed to the module through the Auxiliary Power connector (CN3). The cpuModule only
requires +5 V
DC and ground for operation; however, other modules in the system may require +3.3V, +12 VDC,
–12 V
DC, and –5 VDC. In these instances, the corresponding pins on the Auxiliary Power Connector (CN3) may
be used to supply these voltages.
If using the Auxiliary Power connector to power the system, care must be taken to ensure a good power
connections. The power and ground leads must be twisted together, or as close together as possible to reduce
lead inductance. A separate lead must be used for each of the power pins. Both 5V pins must be connected. The
gauge of wire must be selected taking into account the total power of the system. A good rule of thumb is to use
wire that can supply twice the power required by the system, and do not use less than 18 gauge wire. The length
of the wire must not exceed 3 ft. The power supply solution must be verified by measuring voltage at the
Auxiliary Power Connector and verifying that it does not drop below 4.75 V. The voltage at the connector should
be checked with an oscilloscope while the system is operational.
Note Although it is possible to power the cpuModule through the Auxiliary Power connector, the
preferred method is to power it through the bus connector from a power supply in the stack. The
cpuModule can have large current transients during operation, which make powering it through wires
difficult. Powering through the bus eliminates such problems as voltage drop and lead inductance.
WARNING If you connect power incorrectly, the module will almost certainly be destroyed. Please verify
power connections to the module before applying power.
Table 7 Auxiliary Power Connector (CN3)
1
1. For more information on the ATX style signals, +5V Standby and
PSON#, refer to the Power Management section in Chapter 4, Using
the cpuModule.
Pin Signal Function
1 GND Ground
2 +5 V +5 Volts DC
3 +5V_STDBY +5V Standby (ATX)
4 +12 V +12 Volts DC
5 Reserved Reserved
6 –12 V –12 Volts DC
7 GND Ground
8 +5 V +5 Volts DC
9 GND Ground
10 +3.3 V See note below
11 PSON# Power Supply On (ATX)
12 +3.3 V See note below