Kontron COMe Starterkit Eval T2 - Manual (Page 156)

Power and Reset
3. Power and Reset
3.1. General Power requirements
COM Express calls for the Module to be powered by a single 12V power rail, with a +/-5%
tolerance. The Mini format Modules are specified in COM.0 Rev. 2.1 to support a power input
range of 4.75V to 20.0V. Some vendors offer a wide range input even on Compact and Basic
Modules. COM Express Modules may consume significant amounts of power – 25 to 50W is
common, and higher levels are allowed by the standard. Close attention must be paid by the
Carrier Board designer to ensure adequate power delivery. Details are given in the sections
below.
If Suspend functions such as Suspend-to-RAM, Suspend-to-disk, wake on power button press,
wake on USB activity, etc. are to be supported, then a 5V Suspend power source must also be
provided to the Module. If Suspend functions are not used, the Module VCC_5V_SBY pins
should be left open. On some Modules, there may be a slight power efficiency advantage to
connecting the Module VCC_5V_SBY rail to VCC_5V rather than leaving the Module pin open.
Please contact your Module vendor for further details.
Carrier Boards typically require other power rails such as 5V, 3.3V, 3.3V Suspend, etc. These
may be derived on the Carrier Board from the 12V and 5V Suspend rails.
3.1.1. VCC_12V Rise Time Caution and Inrush Currents
Direct connection of a COM Express Module to a low impedance supply such as a battery pack
may result in excessive inrush currents. The supply to the COM Express Module should be slew
limited to limit the input voltage ramp rate. A typical ATX supply ramps at about 2.5 volts per
millisecond.
PICMG ® COM Express ® Carrier Board Design Guide Rev. 2.0 / December 6, 2013
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