matching question(layout)

[yen]

I have a matching quesition. I want to used in current source.
My question in my pdf file. Please focus on page 3 and 4. Thanks.

 

[yen]

New pdf file.

 

[kapils1982]

where is the PDF file

Added after 4 minutes:

Got the PDF.I would like to know which transistors are similar .Are fingers?

 

[yen]

This permutation is about current sources.
How do I impove the right form.For example : guard ring or other layout material.
My question is how to improve the match of the right form.
Maybe that is better than the left form.
Thank you.

 

[layes2]

just use odd one not even

 

[yen]

just use odd one not even

what is mean? Can you tell detail?
Thanks.
I correct my picture.
Now it is below

This permutation is about current sources.
How do I impove the right form.For example : guard ring or other layout material.
My question is how to improve the match of the right form.
Maybe that is better than the left form.
Thank you.

 

[kapils1982]

The gaurd rings will not help matching because the gaurd ring will only consists of matals and will not efeect eatching of poly and other layers .
We can improve the right form by placing dummy transistors all over the boundary

 

[yen]

The gaurd rings will not help matching because the gaurd ring will only consists of matals and will not efeect eatching of poly and other layers .
We can improve the right form by placing dummy transistors all over the boundary

Dear,
I change my picture. Can this one improve? Are there other methods improving?
Thanks.

 

[franck]

"The gaurd rings will not help matching because the gaurd ring will only consists of matals and will not efeect eatching of poly and other layers ."

But guardring consists of active by definition and so it will help to tie well the substrate and so have quite the same parasitic capacitance to substrate. It seems You need a good guardring if you are looking to have the best matching.

In the last picture the dummies between your 4 block devices in Y and X can be reduce to one row and column. And You can certainly delete them by separating all your device with the same lenght. Don't forget that matching means also proximity. The more your device are close the best it is.

 

[yen]

"The gaurd rings will not help matching because the gaurd ring will only consists of matals and will not efeect eatching of poly and other layers ."

But guardring consists of active by definition and so it will help to tie well the substrate and so have quite the same parasitic capacitance to substrate. It seems You need a good guardring if you are looking to have the best matching.

In the last picture the dummies between your 4 block devices in Y and X can be reduce to one row and column. And You can certainly delete them by separating all your device with the same lenght. Don't forget that matching means also proximity. The more your device are close the best it is.

Don't forget that matching means also proximity. The more your device are close the best it is.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
What do this paragraph mean?
I don't understand clearly.
Do you want to change this picture?Like below.
Besides dummy cells,are there other method in matching cell?
Thanks.

 

[yen]

Beside the above-mentioned question, I have another question.
Below picture, which one have a good match?
And if I have 4 block and 48 current source, is my picture reasonable?
Blanks are dummy cells.

 

[kapils1982]

Dear
I need some clarification:

when u say 48 current sources do u mean that u have 48 separate current sources

OR

Do u have 12 current source for ur DAC with 1 2 3 4 comprising of one current source and so on..............


thanks
kapil

 

[yen]

Dear
I need some clarification:

when u say 48 current sources do u mean that u have 48 separate current sources

OR

Do u have 12 current source for ur DAC with 1 2 3 4 comprising of one current source and so on..............


thanks
kapil

when u say 48 current sources do u mean that u have 48 separate current sources

 

[franck]

What I mean by proximity?
I can't find a best word.
What I want to say is that you don't need to put dummies BETWEEN your 4 devices structure as long as you take care that all you're device and the dummies on the EXTREME edge are separated by the same distance. So by doing this you will improve your matching because your devices will be closer.
Can't be more clear.

 

[kapils1982]

i still did not get you....


a suggestion to the proximity ....Isnt it hat matching is better if the transistors see the same surroundings?

 

[franck]

D = dummy
C = component

____DUMMIES____
D_C1_C2_C3_C4_D
D_C2_C1_C4_C3_D
____DUMMIES____

In fact the dummies on top and bottom ... don't sure it helps ... and of course a good guarding around all that and you should be fine.
This time I can't really be more clear.

Depending on the W and L you can probably switch to a 6 rows and 4 columns instead of 4 rows and 6 columns.

 

[cretu]

Try to get a look on "the art of analog layout" by Hastings..that was uploaded on the site some time ago. That book and another one by Dan Klein explain some basics about matching. In general for current sources(if you have the main source and a replica) should be good enough doing something like
ABBA where A-source, B-replica

Hope this helps

 

[yeewong_su]

For current mirror. just using the common center