ttsgeb
.
- Joined
- Jan 19, 2016
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The xbox has some mildly odd power requirements. It uses the same 20 pin Molex MiniFit Jr connector that an ATX PSU output, however the pinout is completely different.
As it stands, the typical solution is to use a PicoPSU, a small ATX PSU, a modify it to work with the original xbox. PicoPSUs can be had for around $15, the power supplies for them can be had for around $10. It's a very inexpensive solution. Traditionally when this is done, the Power OK and Power On lines are ignored, the PSU is set to always on, and the wires are run all catywumpus to get to where they need to go. While this solution works, it's definitely a hack, and I believe we can do better.
So what are the xbox's actual power requirements?
While I haven't actually cut up a power supply and tried to get the xbox to full load while measuring the current draw, I have a V1.1 PSU here that handily has the power requirements right on the label.
Max Output Power: 96W
DC Output:
+5V -- 13.2A
+3.3V -- 4.8A
+12V --1.2A
+3VSB -- 0.045A
I hope it's safe to assume that further revisions of the xbox had similar or lower power draw. Regardless, this seems like a good starting point.
So, how do I plan to accomplish this?
With 4x LM2678 Regulators from Texas Instruments.
http://www.ti.com/product/LM2678
Why 4 regulators for 3 voltages?
The LM2678 is a 5A regulator. I need 13.2A on the 5V line. Having looked at the specs for the PicoPSUs that seem to work just fine, they're rated for 8A on the 5V line. This leads me to believe that 10A should suffice, so I'll need two regulators for 5V.
I'll also need a 12V regulator, as I plan to run this off of an easily obtainable laptop power supply rather than needing to source an 8A 12V supply.
I will also be designing a smaller footprint alternative that runs off of 12v for when space is of the highest concern. I'll likely also break down the xbox's power requirements even further at some point to see if I can't design a PSU that allows for aggressive trimming, but that's much further down the road.
As it stands, the typical solution is to use a PicoPSU, a small ATX PSU, a modify it to work with the original xbox. PicoPSUs can be had for around $15, the power supplies for them can be had for around $10. It's a very inexpensive solution. Traditionally when this is done, the Power OK and Power On lines are ignored, the PSU is set to always on, and the wires are run all catywumpus to get to where they need to go. While this solution works, it's definitely a hack, and I believe we can do better.
So what are the xbox's actual power requirements?
While I haven't actually cut up a power supply and tried to get the xbox to full load while measuring the current draw, I have a V1.1 PSU here that handily has the power requirements right on the label.
Max Output Power: 96W
DC Output:
+5V -- 13.2A
+3.3V -- 4.8A
+12V --1.2A
+3VSB -- 0.045A
I hope it's safe to assume that further revisions of the xbox had similar or lower power draw. Regardless, this seems like a good starting point.
So, how do I plan to accomplish this?
With 4x LM2678 Regulators from Texas Instruments.
http://www.ti.com/product/LM2678
Why 4 regulators for 3 voltages?
The LM2678 is a 5A regulator. I need 13.2A on the 5V line. Having looked at the specs for the PicoPSUs that seem to work just fine, they're rated for 8A on the 5V line. This leads me to believe that 10A should suffice, so I'll need two regulators for 5V.
I'll also need a 12V regulator, as I plan to run this off of an easily obtainable laptop power supply rather than needing to source an 8A 12V supply.
I will also be designing a smaller footprint alternative that runs off of 12v for when space is of the highest concern. I'll likely also break down the xbox's power requirements even further at some point to see if I can't design a PSU that allows for aggressive trimming, but that's much further down the road.
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