two different guard ring

[erikl]

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

I'd think guardRings should be used for screening

• parts which generate exceedingly high levels of EMI
• parts which are particularly sensible against EMI

... i.e. for both digital & analog parts, if necessary due to these criteria.

 

[deepak242003]

b facilitates routing wiht metal1 , if the block below is not sensitive enough...

 

[sunils]

If you really want to seperate substrate between analog blocks and digital blocks, All I know is to use triple-well guardring.
by the way, what is box-shielding?

 

[solidstate]

What kind of ground does one connect to guard rings? Should it be clean (analog) or digital? If you're protecting analog circuits, I think it should be gnda, but if you're fencing off a digital block, it should be gndd, right?

 

[karesz]

...I'd think guardRings should be used for screening....

I would say; you can use it as screening, but its idea is originally for limit/stop currents from/to another parts of your circuits/PCB & Chip surfaces...
What you means is (for me) more a GND ring (w. appropriate contacting on systems base/ GNDs, these is usable for screening...
Regards!
K.

 

[dick_freebird]

Guard rings may have multiple purposes.

One is to shunt away substrate noise currents. That would
be served as well by (B) as (A).

Another it to make a DC tie for every single body of every
transistor. There are tie-proximity rules that have to be met.
It seems possible that tbe devices at the bottom of (B) might
not have as good a tie. That comes down to the final layout.

Unless you're in a lose-a-penny-per-die kind of business,
there's no such thing as too good a guardring.

 

[Azmi]

if the digital circuit has a latch-up issue, then guard ring type A is prefered. maybe type b is usable if the analog circuit is far enough from the digital circuit or it is located at the edge of the die. and i don't think the guard ring took very large area.