Adding more power to a VME Rack

[Brocktune]

The power supply of this VME rack I'm using doesn't put out enough current on the 3.3Volts to power a board I'm going to use. So...I'm just going to buy a seperat ATX power supply and power half of the 3.3V pins on the board with it. The other half of the board will be getting power from the P1 Row D pins like normal.

I figure as long as I join the Grounds of the ATX and the VME power supply, then I should be okay. But I'm not sure if it's good to mix and match like that. Need advice.

 

[crust]

On my vme boards, I usually use a DC/DC converter from +12 or +5 to whatever voltage I need.

 

[Sebi]

Basically i agree with crust: use a simple buck converter from 12V, this output have always reserve power. When You apply another PSU, cannot loading only the 3.3V output, You must always loading the 5V output min. 1...2A.

 

[Brocktune]

Thank you Crust and Sebi,

Hey, Sebi, I am 25% Hungarian

Thank you for your replies...my VME power situation has turned out to be simpler than I expected. I am adding a VME board to a VME slot, but this new board will not be using the VME power or communicating on the VME bus. It will plug into the P1 and P2 connectors on the motherboard, but I will be running separate power to twelve of the "User Defined" pins on the backplane with a daughterboard connector. I will, of course make the ground common between the VME power supply and the daughterboard connector power supply. I have chosen to power the extra board with an ATX 200 Watt power supply. I needed at least 10 amps on the 3.3V.

But more suggestions are welcome if anyone has any!

 

[crust]

You'll have to use multiple pins, the max current on any pin in the VME bus is 2A.