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How to design the transistor size in this latch?

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turtlewang

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Hello everyone,

I am studying the design of frequency divider. I have met a latch architecture shown in the following figure. Does anybody know the name of this type of latch?

What are the advantages of this type of latch over the CML latch?

And How do I size the transistors in the latch?

Can anybody give me some materials about latch design?

Thanks very much!
latch.giflatch.gif
latch.gif
 
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AdvaRes

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This is a full swing cross-coupled NMOS latch.

You can learn more about it from this paper:
"AN OVERVIEW OF LOW-VOLTAGE VCO DELAY CELLS AND A WORST-CASE
ANALYSIS OF SUPPLY NOISE SENSITIVITY"
Mohamad El-Hage and Fei Yuan
 

turtlewang

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thanks, but how about the latter one, how do i size the trnasistor?
 

AdvaRes

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The second is a differential latch with resistive load.
Sizing your transistor depends only on the speed requirement. If you'll use this prescaler in PLL you have to pay care also to noise contribution.
 

dgnani

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Hello everyone,

I am studying the design of frequency divider. I have met a latch architecture shown in the following figure. Does anybody know the name of this type of latch?

What are the advantages of this type of latch over the CML latch?

And How do I size the transistors in the latch?

Can anybody give me some materials about latch design?

Thanks very much!
View attachment 57883View attachment 57883
View attachment 57885
As a general rule, the control FETs have to be 'stronger' (higher beta) than the cross-coupled FETs so they define the node voltages during current-contention programming
 

turtlewang

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thanks,

Can you give me more details about the relationship between speed and transistor size and the noise contribution? Or can you recommend me some papers or books?

Thanks again!

The second is a differential latch with resistive load.
Sizing your transistor depends only on the speed requirement. If you'll use this prescaler in PLL you have to pay care also to noise contribution.


---------- Post added at 12:55 ---------- Previous post was at 12:44 ----------

unfortunately, I don't have the book! so sad!
 

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