DDR termination voltage

Oct 09, 2011 27 Replies

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

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.

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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?

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

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 f*ck 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

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 nothing), asking a question and arguing that your answer is correct (it's not) is moronic.

Now, go away.

...and then argue the answer? Moron.

What a loon.

Plonk

You can't have a sense of humor, if you have no sense.

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.

You bet! The .est.

Blame your parents for stupid. I wasn't there.

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.

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

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

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 they ask a question.

You're being "punished" because you're acting like an arrogant little trolling asshole. Or maybe it's not an act?

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

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