Power Considerations
CP307
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ID 34424, Rev. 3.0
P R E L I M I N A R Y
5.1.2
Backplane
Backplanes to be used with the CP307 must be adequately specified. The backplane must pro-
vide optimal power distribution for the +3.3 V, +5 V and +12 V power inputs. It is recommended
to use only backplanes which have at least two power planes for the +3.3 V and +5 V voltages.
Input power connections to the backplane itself should be carefully specified to ensure a mini-
mum of power loss and to guarantee operational stability. Long input lines, under dimensioned
cabling or bridges, high resistance connections, etc. must be avoided. It is recommended to
use POSITRONIC or M-type connector backplanes and power supplies where possible.
5.1.3
Power Supply Units
Power supplies for the CP307 must be specified with enough reserve for the remaining system
consumption. In order to guarantee a stable functionality of the system, it is recommended to
provide more power than the system requires. An industrial power supply unit should be able
to provide at least twice as much power as the entire system requires. An ATX power supply
unit should be able to provide at least three times as much power as the entire system requires.
As the design of the CP307 has been optimized for minimal power consumption, the power
supply unit must be stable even without minimum load.
Where possible, power supplies which support voltage sensing should be used. Depending on
the system configuration this may require an appropriate backplane.
The start-up behavior of CPCI and PCI (ATX) power supplies is critical for all new CPU boards.
These boards require a defined power sequence and start-up behavior of the power supply. For
information on the required behavior refer to the power supply specifications on the formfac-
tors.org web site and to the CompactPCI (PICMG) specification on the picmgeu.org web site.
5.1.3.1
Start-Up Requirement
Power supplies must comply with the following guidelines, in order to be used with the CP307.
• Beginning at 10% of the nominal output voltage, the voltage must rise within
> 0.1 ms to < 20 ms to the specified regulation range of the voltage. Typically:
> 5 ms to < 15 ms.
• There must be a smooth and continuous ramp of each DC output voltage from
10% to 90% of the regulation band.
• The slope of the turn-on waveform shall be a positive, almost linear voltage increase and
have a value from 0 V to nominal Vout.
Note ...
Non-industrial ATX PSUs may require a greater minimum load than a single
CP307 is capable of creating. When a PSU of this type is used, it will not
power up correctly and the CP307 may hangup. The solution is to use an
industrial PSU or to add more load to the system.
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