Decap cell Estimation.

[arjun1110]

decap cell

Hi,

Can anybody tell how to estimate the total number of decap cells in a design?

Regards,

 

[tariq786]

add decap

Hmm. I think i am not well qualified to answer this. But i think it depends upon the maximum power supply droop experienced in a design because of instantaneous current drawn from the vdd supply rail.

So in short, estimate depends upon the maximum voltage supply droop which depends upon the maximum instantaneous current drawn by the design.

Please google more.

Good luck

 

[arjun1110]

ir drop decap

Thanks Tariq.

Regards,

 

[hiral.kotak]

decap cell design

Hi,

Decap cells can help to reduce IR drop or reduce noise in mixed signal designs.adding these decoupling capacitance to a design can help maintain a stable voltage between power and gnd when signal nets switch. This can reduce IR drop for power nets and limit bouncing on ground nets. So for the estimation of number of decaps in ur design u need to first analyze ur power consumption and then need to deside according to ur supply voltage and drop.

It may help u.

Thanks..

HAK..

 

[arjun1110]

decap ir drop

Thanks HAK.

 

[archillios]

ir drop

I am concerning with this problem also.
More Decap can improve IR Drop issues, but more leakage will occur.
How to balanced these two factor? Any experience?

 

[mvvijay78]

how leakage in decap

I believe you first need to do a dynamic IR drop analysis to come up with the estimate of the amount of decaps required and the area where they are required. In the process above 130nm actually lot of people just go ahead and add decaps similiar to fillers without actually calculating the IR. The reason it works at this technology is that the leakage current impact is not that much. But below 90nm this process can no longer be followed and it needs to run the IR drop analysis

 

[designer_ec]

decap leakage

Hi,
Here I have one doubt,is there any rule for puttining decap cells in design? I mean is there any rule that we have to place decap cell in specific distance?