# DDR termination voltage

V

#### valtih1978

Jan 1, 1970
0
I read on termination topics and they say that having Vtt equal to the
high-to-low transition level is a bad idea (tristated buses will
noise-switch all the readers and, thus, consume unnecessary power). Yet,
JEDEC prescribes using 1.25 Vtt for DDR, based on 2.5 volt SSTL_2
signaling. Why?

K

#### [email protected]

Jan 1, 1970
0
I read on termination topics and they say that having Vtt equal to the
high-to-low transition level is a bad idea (tristated buses will
noise-switch all the readers and, thus, consume unnecessary power). Yet,
JEDEC prescribes using 1.25 Vtt for DDR, based on 2.5 volt SSTL_2
signaling. Why?

Minimum terminator power? P=V^2/R

V

#### valtih1978

Jan 1, 1970
0
Minimum terminator power? P=V^2/R

consume more to save more!

K

#### [email protected]

Jan 1, 1970
0
consume more to save more!

Huh? With the terminator in the middle, you save half the power (twice as
many lines, on average, 1/4 power each). The I/O obviously can't have an
issue being "hung up" in the middle.

V

#### valtih1978

Jan 1, 1970
0
http://web.cecs.pdx.edu/~greenwd/xmsnLine_notes.pdf explains the "issue":

"For three-state buses, the Théven in equivalent voltage, VThev, may be
chosen to yield a valid logic level when the bus is not being driven. It
is especi ally important in this case to choose a voltage that is not
close to the switching threshold of the receivers, lest they draw
excessive current or oscillate."

K

#### [email protected]

Jan 1, 1970
0
http://web.cecs.pdx.edu/~greenwd/xmsnLine_notes.pdf explains the "issue":

"For three-state buses, the Théven in equivalent voltage, VThev, may be
chosen to yield a valid logic level when the bus is not being driven. It
is especi ally important in this case to choose a voltage that is not
close to the switching threshold of the receivers, lest they draw
excessive current or oscillate."

....or are disabled when in the tristate condition. You know more than the
memory (bus) developers?

K

#### [email protected]

Jan 1, 1970
0
http://web.cecs.pdx.edu/~greenwd/xmsnLine_notes.pdf explains the "issue":

"For three-state buses, the Théven in equivalent voltage, VThev, may be
chosen to yield a valid logic level when the bus is not being driven. It
is especi ally important in this case to choose a voltage that is not
close to the switching threshold of the receivers, lest they draw
excessive current or oscillate."

BTW, if you know everything, why are you here?

V

#### valtih1978

Jan 1, 1970
0
Only those who do not understand experts ask questions. Those, who ask
to explain the reason behind expert decisions, should not ask the questions.

R

#### Rich Grise

Jan 1, 1970
0
valtih1978 said:
Only those who do not understand experts ask questions. Those, who ask
to explain the reason behind expert decisions, should not ask the
questions.

Have you ever gone outside and played "hide and go **** yourself?"

The only stupid question is the one you don't ask.

And the most important thing anyone can learn in life is to question
authority.

Hope This Helps!
Rich

V

#### valtih1978

Jan 1, 1970
0
It seems that giving answers to asked questions I make people crazy.

K

#### [email protected]

Jan 1, 1970
0
It seems that giving answers to asked questions I make people crazy.

You asked the question, moron. If you think you know everything (you know
is moronic.

Now, go away.

K

#### [email protected]

Jan 1, 1970
0
Only those who do not understand experts ask questions.

....and then argue the answer? Moron.
Those, who ask to explain the reason behind expert decisions,

What a loon.

R

#### Rich Grise

Jan 1, 1970
0
valtih1978 said:
It seems that giving answers to asked questions I make people crazy.

I am a mirror.

V

#### valtih1978

Jan 1, 1970
0
Those, who ask to explain the reason behind expert decisions,
What a loon.

Stupid thing? But, this is what you taught me. BTW, next time you hear
anybody asking a question, do not tell him that he knows everything.
Only morons and loons may come to such conclusion.

K

#### [email protected]

Jan 1, 1970
0
Stupid thing?

You bet! The .est.
But, this is what you taught me.

Blame your parents for stupid. I wasn't there.
BTW, next time you hear anybody asking a question,
do not tell him that he knows everything.

Now you're telling me what I must do? That stupid streak runs deep.

You think you do. That's the point. Why you asked the question, in the first
place, will never be known to the sane.
Only morons and loons may come to such conclusion.

No, only a moron asks a question then argues the answer like they know-it-all.
Indeed, you are both.

K

#### Kaz Kylheku

Jan 1, 1970
0
Only those who do not understand experts ask questions. Those, who ask
to explain the reason behind expert decisions, should not ask the questions.

On the flipside, those who refuse to explain their conclusions are not
experts.

V

#### valtih1978

Jan 1, 1970
0
No, only a moron asks a question then argues the answer like they know-it-all.
Indeed, you are both.

I pointed your attention to the "issue" that my question is about. You
started to attack me because of that. You punish people just because

V

#### valtih1978

Jan 1, 1970
0
You're being "punished" because you're acting like an arrogant little
trolling asshole.

If you dare to ask you question in this group, you act like a trolling
arrogant assole. Thank you for reminding me this.

V

#### valtih1978

Jan 1, 1970
0
I do not think that I must be happy or shut up and get away after the
first response. The first response provided at important aspect. But, it
completely disregards the aspect I wanted to be clarified. It is normal
to ask people to take the OP-requested aspect into consideration and,
BTW, explain what I mean by "draw more power to save power" to the first
replier.

I'm asking here because I do not see a special group on memory/source
synchronous topics. If there is something wrong with this way of acting
then why I should try creating another thread (in another place?)?

V

#### valtih1978

Jan 1, 1970
0
The short answer is, "You shouldn't."

Thank you for confirming my guess once more.

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