Hi,
we build a custom cRIO-module based on the C-series Module Development Kit (MDK):
- We need more than 200 mA on the 5 V supply
- We don't have room for a front-panel supply
The module will be used in a custom application and will not be sold on the market.
We can guarantee that neigboring cRIO-slots are empty. If so, can we draw more than 200 mA (i.e., 400 mA)?
Below is an earlier response I received through the Swiss NI representative, Mr. Rudolph. This response does not talk about leaving neighboring slots empty.
Thanks,
Daniel Engeler
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They cannot violate the power draw (200mA) from the backplane. If they
draw more than the 200 mA, it will take power from other modules. This
could cause those modules to not operate correctly, compromising all
guarantees and all of our specifications would no longer be valid.
Additionally, it could cause the backplane to be unstable. It could
even cause damage. Furthermore, they cannot sell it on the market like
this. It would never pass our platform certifications.
I think that the wording in the MDK manual clearly states this and is
clearly saying do not do this:
The power to a module can range from 4.75 V to 5.25 V. The module must
stay within this voltage range while meeting all performance
specifications. The design of the module must guarantee that the peak
current driven from the chassis remains between 0 mA and 200 mA. The
peak current is the absolute maximum current draw from the Power pin,
taking into account worst-case conditions of the power supply voltage,
module operating conditions, and module tolerances. Peak current is
the maximum current that you can observe if measuring current with a
low-pass filter with two poles at 10 kHz. The design of the module
must ensure that the peak current consumption remains under 200 mA,
even when the wiring is in the worst-case combination of short
circuits or under/overvoltage conditions.
However, many customers have built modules that require more power by
having the end user hook up their own external power. They will want
to be isolated from the backplane, which I think most customers do
anyway, and then just put the connectors for more power on the front
of the module.
