Power Rail Supply for FACE Module

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Power Rail Supply for FACE Module

Post by drz113 »

In your "FACE Module Design Guide", it states the maximal current consumption from the 12V power rail should not exceed 1A and the 5V power rail should not exceed 2A. Is this true? On the LAN schematic when I add up all of the possible DC-DC outputs, it comes out to be approximately 18W which exceeds the allowed 12W(12V power rail) output.

I'm trying to connect an external graphics card via PCIe on a custom FACE module and the supply I need is not feasible with the current ratings stated.

Would it make more sense to just bring in an additional 12V line directly to the FACE Module? I could switch it on let's say when the 5V supply line goes high.


Re: Power Rail Supply for FACE Module

Post by mbirger »

It is not exactly correct and will be fixed.
In future please refer to FACE module HW spec document which is the most updated technical reference material.
12V rail from the Host board to the FACE module supplied via 8 pins of the B2B connector (each rated for 1A max current, unregulated directly from the main power supply, but after some noise rejection via ferrite beads.

Under 90% OS load conditions without USB bus powered devices attached, Intense consume ~26W (12V @ 2.16A). Attaching USB bus powered devices may increase this value (you may calculate by how much taken 12V to 5V DC/DC conversion with 90% efficiency let say). But I assume at normal use you won't exceed the 3A from 12V totally.

Two cases:
1. If you're using your own power supply, 12V current ratings limited only by the output power capabilities of the PS and maximum current pass through B2B connectors which is 8A.
2. If you're using Intense PC native PS, it is 60W output (12V @ 5A).
So after deducting system consumption, you're left up to ~2.5A to use from that rail.

I would not go to the limit of the PS, but it guarantees your 18W.

5V power supply also let you use much more than 2A, but it should be remembered that 5V is a regulated output from DC/DC and that its input current is taken from 12V .

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