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About PCI power supply

O

oxy

Jan 1, 1970
0
If I use 5V connector slot.
Could I use 3.3v component in PCI add-in Card without any power regulator ?
please tell me,thanks.

ps:I had confused with power management long time.

Best Regards.
 
K

Ken Taylor

Jan 1, 1970
0
oxy said:
If I use 5V connector slot.
Could I use 3.3v component in PCI add-in Card without any power regulator ?
please tell me,thanks.

ps:I had confused with power management long time.

Best Regards.

No.

Ken
 
R

Robert Baer

Jan 1, 1970
0
oxy said:
If I use 5V connector slot.
Could I use 3.3v component in PCI add-in Card without any power regulator ?
please tell me,thanks.

ps:I had confused with power management long time.

Best Regards.

As Ken said, the general answer is "no"; most parts would be desroyed
by the overvoltage.
Be safe and use a regulator.
 
O

oxy

Jan 1, 1970
0
Robert Baer said:
As Ken said, the general answer is "no"; most parts would be desroyed
by the overvoltage.
Be safe and use a regulator.

Ya.......it's so bad news!
but i still have a question for this.
In PCI Spec,i saw the pins of 3.3v & 5v are in 5-volt add-in PCI card?
what does it mean? Or 3.3v pin is reserved in 5v add-in PCI card?
please tell me,thanks.

Best Regards.
 
K

Ken Taylor

Jan 1, 1970
0
oxy said:
Ya.......it's so bad news!
but i still have a question for this.
In PCI Spec,i saw the pins of 3.3v & 5v are in 5-volt add-in PCI card?
what does it mean? Or 3.3v pin is reserved in 5v add-in PCI card?
please tell me,thanks.

Best Regards.

What is it that you are actually trying to do? The PCI spec for 3.3V refers
to the signalling - what you do on the board once the signal gets there is
your business. However, if you have a 3.3V component you need to supply is
with 3.3V - regulators are small and cheap.

Ken
 
O

oxy

Jan 1, 1970
0
Ken Taylor said:
What is it that you are actually trying to do? The PCI spec for 3.3V refers
to the signalling - what you do on the board once the signal gets there is
your business. However, if you have a 3.3V component you need to supply is
with 3.3V - regulators are small and cheap.

Ken

ok ok ~ ~
I suppose it that 5V slot can't support 3.3v even 1.8v.
so only I can do is that put 2 regulators to transfer it.
And I konw regulator is so cheap, but my company wants me cost down do
my best.
So in my Rev1.0 PCI add-in card,I must have 2 regulator to support
3.3v & 1.8v Component to work.
or Not?
 
R

Robert Baer

Jan 1, 1970
0
oxy said:
Ya.......it's so bad news!
but i still have a question for this.
In PCI Spec,i saw the pins of 3.3v & 5v are in 5-volt add-in PCI card?
what does it mean? Or 3.3v pin is reserved in 5v add-in PCI card?
please tell me,thanks.

Best Regards.

I do not know about the PCI spec, have not looked at it.
But, if one of the pins is speced at 3.3V, then one might assume that
it could be used as a power source.
Just limit the current to 100 mA if possible, with a 500mA absolute
max surge.
 
R

Robert Baer

Jan 1, 1970
0
oxy said:
ok ok ~ ~
I suppose it that 5V slot can't support 3.3v even 1.8v.
so only I can do is that put 2 regulators to transfer it.
And I konw regulator is so cheap, but my company wants me cost down do
my best.
So in my Rev1.0 PCI add-in card,I must have 2 regulator to support
3.3v & 1.8v Component to work.
or Not?

From your questions, it appears that you do not know enough to even
touch this "project" of yours.
I seem to remember that at least once, you weer told that seperate
regulators were needed.
And if you knew electronics, then you would not have asked that
question, and would be able to determine if those line(s) that mentioned
3.3V were signal or power.
 
K

Ken Taylor

Jan 1, 1970
0
oxy said:
ok ok ~ ~
I suppose it that 5V slot can't support 3.3v even 1.8v.
so only I can do is that put 2 regulators to transfer it.
And I konw regulator is so cheap, but my company wants me cost down do
my best.
So in my Rev1.0 PCI add-in card,I must have 2 regulator to support
3.3v & 1.8v Component to work.
or Not?

There are prototyping boards with PCI interface included, with prototyping
area for you to develop your circuit on. This may be an easier way to do it
as the VLSI on-board already handles the bus interface.

Ken
 
O

oxy

Jan 1, 1970
0
Robert Baer said:
I do not know about the PCI spec, have not looked at it.
But, if one of the pins is speced at 3.3V, then one might assume that
it could be used as a power source.
Just limit the current to 100 mA if possible, with a 500mA absolute
max surge.

Yesterday,I got news about 3.3v pins in PCI 2.0~2.3 from my teacher(he
got the news from MB Manufactor).
He said that if MB is PCI 2.x,so user can use 3.3v power supply from
5v slot.
And Imax=4.5A.
But my boss and teacher tell me that we have to place 2 regulators to
transfer 3.3v & 1.8v.
So......it's terrible news for me.....oh!!god!!
 
K

Ken Taylor

Jan 1, 1970
0
oxy said:
Yesterday,I got news about 3.3v pins in PCI 2.0~2.3 from my teacher(he
got the news from MB Manufactor).
He said that if MB is PCI 2.x,so user can use 3.3v power supply from
5v slot.
And Imax=4.5A.
But my boss and teacher tell me that we have to place 2 regulators to
transfer 3.3v & 1.8v.
So......it's terrible news for me.....oh!!god!!

*Why* is this terrible?? There's plenty of single-component regulators out
there which will do the trick: eg.
http://www.sipex.com/products/pdf/SPX5205.pdf
Two of these, problem gone. And I bet Maxim do a single-chip solution for
all your power supply levels.

And don't forget that it's only the bus that's 3.3V so a suitable interface
chip will remove the bus from the equation.

Ken
 
R

Robert Baer

Jan 1, 1970
0
oxy said:
Yesterday,I got news about 3.3v pins in PCI 2.0~2.3 from my teacher(he
got the news from MB Manufactor).
He said that if MB is PCI 2.x,so user can use 3.3v power supply from
5v slot.
And Imax=4.5A.
But my boss and teacher tell me that we have to place 2 regulators to
transfer 3.3v & 1.8v.
So......it's terrible news for me.....oh!!god!!

There aint no PCB contacts that can reliably handle 4.5 *amps* !!
In fact i would not trust a single contact with any current over
500mA, and it would have to be a multiple contact, *NOT* a single point
like some Molex connectors.
Work on the basis of a contact resistance of 10 milliohms.
Yes, the typical may less, but if there is ever any fault that makes a
contact go higher, then one certainly does not want I*R heating to
aggrivate the problem.
 
R

Robert Baer

Jan 1, 1970
0
Ken said:
*Why* is this terrible?? There's plenty of single-component regulators out
there which will do the trick: eg.
http://www.sipex.com/products/pdf/SPX5205.pdf
Two of these, problem gone. And I bet Maxim do a single-chip solution for
all your power supply levels.

And don't forget that it's only the bus that's 3.3V so a suitable interface
chip will remove the bus from the equation.

Ken

Like i have said before *forget* Maxim!
They do not want to make parts they advertise, unless you have tens of
thousands of dollars to commit to one of their many un-available parts,
and 6-20 months of lead time.
Many distributors refuse to carry any of the Maxim line due to this
problem.
 
O

oxy

Jan 1, 1970
0
Robert Baer said:
There aint no PCB contacts that can reliably handle 4.5 *amps* !!
In fact i would not trust a single contact with any current over
500mA, and it would have to be a multiple contact, *NOT* a single point
like some Molex connectors.
Work on the basis of a contact resistance of 10 milliohms.
Yes, the typical may less, but if there is ever any fault that makes a
contact go higher, then one certainly does not want I*R heating to
aggrivate the problem.

My company decides to use 3.3v pin to support all component in PCI
add-in Card.
So i have to find a power regulator to transfer 3.3v to 1.8v, but the
IC isn't easy to buy in material store.
But i don't think it difficult to search.
The point is how to compute total current in a component (ex. Flash
ROM,EEPROM,PHY....).
Although I have spec about all component,but i still don't know how to
konw total current(it means a component that i need to supply max
current)
Can or Could any one help me to answer this stupid question?thanks.
 
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