PS-ON questions.

futRtrubL · 02-05-2002, 10:46 PM

Looking on the web I was told that when PS-ON is high PSU is off and when PS-ON is low PSU is on. Is this correct? Also what are the high and low values of PS-ON?
Also if I run something off +5Vsb can I attach my circuits ground to any ground wire?

Edward

GigaFrog · 02-05-2002, 11:07 PM

ATX Specs from Desktop FF

Page 19 section 3.3.2. explains the PS_ON signal functionnality.
Notice that it is not necessariliy high, but may just be opened when the PSU is off. The table says Vhigh is 2V min. It also says that the PSU shall have an internal pull up, so you don't have to provide any voltage, just to release this signal from ground.

For the 5VSB, I believe you can use any ground wire. Section 3.3.3. does not say much.

Hope this help.

futRtrubL · 02-06-2002, 11:03 AM

Thanks GigaFrog, I was fed up searching for that info. ;']

This no begs the question: Does the momentary power switch pull its output to low when pushed or to high? Also, is it the same 5V logic? I looked on that same site but I couldn't find that info.

Edward

GigaFrog · 02-06-2002, 11:35 AM

The momentary power switch pulls to ground when you press it. It actually connects its to leads together, one of these leads being permanent ground, the other has a pull up resistor to 5VSB (I think).
I would guess it is the same 5V logic (form the same 5VSB, the only voltage active when the system is off).
The power switch does not provide any logic signal. It is closed or opened. Once closed, it triggers a flip-flop that will generate the PS-ON signal.

That's how I understand it.
Make a search on ATX motherboard, I am at work now and have no time to search.

Good luck.

futRtrubL · 02-06-2002, 12:41 PM

Thanks for all the help GigaFrog!

Edward

02-05-2002, 10:46 PM	#1
futRtrubL Cooling Savant Join Date: Jul 2001 Location: Kingston, Jamaica Posts: 204	PS-ON questions. Looking on the web I was told that when PS-ON is high PSU is off and when PS-ON is low PSU is on. Is this correct? Also what are the high and low values of PS-ON? Also if I run something off +5Vsb can I attach my circuits ground to any ground wire? Edward

02-05-2002, 11:07 PM	#2
GigaFrog Cooling Neophyte Join Date: Nov 2001 Location: NorthWest (French & US) Posts: 88	ATX Specs from Desktop FF Page 19 section 3.3.2. explains the PS_ON signal functionnality. Notice that it is not necessariliy high, but may just be opened when the PSU is off. The table says Vhigh is 2V min. It also says that the PSU shall have an internal pull up, so you don't have to provide any voltage, just to release this signal from ground. For the 5VSB, I believe you can use any ground wire. Section 3.3.3. does not say much. Hope this help. __________________ Got water? Water cooled for 3 years. Safe with thermal switch. Now silent with fan thermostat.

02-06-2002, 11:35 AM	#4
GigaFrog Cooling Neophyte Join Date: Nov 2001 Location: NorthWest (French & US) Posts: 88	The momentary power switch pulls to ground when you press it. It actually connects its to leads together, one of these leads being permanent ground, the other has a pull up resistor to 5VSB (I think). I would guess it is the same 5V logic (form the same 5VSB, the only voltage active when the system is off). The power switch does not provide any logic signal. It is closed or opened. Once closed, it triggers a flip-flop that will generate the PS-ON signal. That's how I understand it. Make a search on ATX motherboard, I am at work now and have no time to search. Good luck. __________________ Got water? Water cooled for 3 years. Safe with thermal switch. Now silent with fan thermostat.

02-06-2002, 11:03 AM	#3
futRtrubL Cooling Savant Join Date: Jul 2001 Location: Kingston, Jamaica Posts: 204	Thanks GigaFrog, I was fed up searching for that info. ;'] This no begs the question: Does the momentary power switch pull its output to low when pushed or to high? Also, is it the same 5V logic? I looked on that same site but I couldn't find that info. Edward

02-06-2002, 12:41 PM	#5
futRtrubL Cooling Savant Join Date: Jul 2001 Location: Kingston, Jamaica Posts: 204	Thanks for all the help GigaFrog! Edward

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