two different guard ring

[sj95]

Dear all:

If I have the below two floor plan, will the guard ring B work well as guard ring A ?

THX



Guard ring A (enclose all analog):

Digital
________
| Analog|
| Analog|
|______|



Guard ring B (the furthest guard ring is ignored):

Digital
_______
|Analog|
|Analog|



thanks

 

[skymusic]

Guard ring A is better.

 

[sj95]

yes, I know A is better.
But B is useless ?

 

[LovNike]

Guard ring B also apart analog blocksand digital block.

 

[eng_Semi]

If the digital is only on the top, both guard rings are the same (from my point of view)

 

[ashutoshdeenanath]

guard ring A is better bcoz substrate will same and noise will come from substrate and if guard ring is break then it will create problems

 

[scottieman]

should a guard ring surrounding the digital circuits more efective than that surrounding the analog part?

 

[Brittoo]

Dear all:

If I have the below two floor plan, will the guard ring B work well as guard ring A ?

THX



Guard ring A (enclose all analog):

Digital
________
| Analog|
| Analog|
|______|



Guard ring B (the furthest guard ring is ignored):

Digital
_______
|Analog|
|Analog|



thanks

Hi sj95

In my opinion, guardring A is preferable coz chances of circuit elements talking to each other(noise) through substrate is much reduced.
Guard ring B is not useless though. Every guardring would have its effects upto certain distance varying for different processes. So, if you have ur analog 2 within that vicinity, you could ignore the farthest guardring.
Now, its upto you if you want to go for better performance or save space at the cost of performance.
Hope that has answered ur question. Have a gr8 day!!!

Regards
Brittoo

 

[leohart]

Hi,even we use the guard ring A,will the noise coupled into analog part from the substrate right under it? We know the digital and analog are on the same sub,the guard ring give isolation only to certain to depth of sub.

 

[Brittoo]

Hi,even we use the guard ring A,will the noise coupled into analog part from the substrate right under it? We know the digital and analog are on the same sub,the guard ring give isolation only to certain to depth of sub.

hi leohart

If the net is noisy / critical one then , you could go for shielding(box shielding preferably) with power rauils. that wud definitely help. isolate the quiet analog from the noisy digital part .

regards
Brittoo

 

[careking]

A is better

 

[leohart]

Hi,even we use the guard ring A,will the noise coupled into analog part from the substrate right under it? We know the digital and analog are on the same sub,the guard ring give isolation only to certain to depth of sub.

hi leohart

If the net is noisy / critical one then , you could go for shielding(box shielding preferably) with power rauils. that wud definitely help. isolate the quiet analog from the noisy digital part .

regards
Brittoo

hi my question is "will noise be coupled from the substrate right under even though we have used guardring"...the analog part in the guardring is still connect with noisey part through "the substrate right under analog part->substrate under guardring->substrate of noisey part"
I dont know if I have make myself clear...

Anyway,what is a box shielding?What's the difference between this one and guardring

THX!

 

[Brittoo]

Hi,even we use the guard ring A,will the noise coupled into analog part from the substrate right under it? We know the digital and analog are on the same sub,the guard ring give isolation only to certain to depth of sub.

hi leohart

If the net is noisy / critical one then , you could go for shielding(box shielding preferably) with power rauils. that wud definitely help. isolate the quiet analog from the noisy digital part .

regards
Brittoo

hi my question is "will noise be coupled from the substrate right under even though we have used guardring"...the analog part in the guardring is still connect with noisey part through "the substrate right under analog part->substrate under guardring->substrate of noisey part"
I dont know if I have make myself clear...

Anyway,what is a box shielding?What's the difference between this one and guardring

THX!

hi leohart

Since substrate is the floor for the entire chip, noise coupling through the substrate is unavoidable and our aim is to reduce this as much as possible. Deep N wells are used for this purpose in certain processes. Double guardring, triple guardrings are also used.
Box shielding would have a power rail underneath and on both the adjacent sides of a critical signal (below, left and right). Its very useful to protect ur circuit from noisy signals that hav to be separated from the rest of the circuit.
Hope that helps. Any comments are welcome.

regards
Brittoo

 

[leohart]

Now I know what is a boxing shielding,it is only available for signal line,not for circuitry on substrate.

Since guard ring cannot get rid of sub coupling entirely,we should use DNW for most noise ciritical part...

Can you explain what is a triple guard ring look like?

I usaually use only a vdd tie-uped nwell surround analog part, can this(we can call it single guard ring) configuration provide enough isolation comparing to double guard ring?The double guard ring uses another p+/sub gnd tiedown around,but the sub is on gnd already...I'm not sure if this tiedown is must?

THX!

 

[xwcwc1234]

Guard A is better . But if there are no digital circuit below the analog circuits or anaolog circuits place approach chip corner , there is no diference, I think.

 

[williamy]

some papers comment one/two/three
guard rings.guanrd rings are used to absorb the noise in the substrate in the neighbor

 

[beckchm]

of course A is better , some noise possibly inject into the analog section

 

[psmon]

If the guard ring between analog and digital sections is narrow, both cases don't matter much.

 

[deepak242003]

should a guard ring surrounding the digital circuits more efective than that surrounding the analog part?

guard ring surrounding analog portion is first preference if the layour space is limited

 

[kapilsn]

Shouldnt the digital part be surrounded by gaurdrings instead of analog??Why not??