Can power gating technique reduce IR?

[alam4vlsi]

Hi,

Can power gating (adding power switches in worst IR drop region) technique reduce IR Drop? I have Worst IR Drop under always on metal layer... In this case, can i add power switches under always on metal layer? Waiting for reply and Thanks in advance

 

[rca]

Re: Doubt Regarding IR Drop Analysis

well, you will improve your IR Drop is your switch is open, but in this case, do you need this logic?
If your power routing is not enought strong to support the consumption of your element, you need to add connection, if you have limited resource available to add power connections, you could tried to connected the metal filling to the power nets to help and reduce the IR drop.

 

[alam4vlsi]

Re: Doubt Regarding IR Drop Analysis

please... Can you explain more in detail?

 

[owen_li]

Re: Doubt Regarding IR Drop Analysis

Actually, I think power gating technique will make the IR drop much worse. Coz the resistance on power switch cells is much bigger, corresponding to the power distribution network

 

[rca]

Re: Doubt Regarding IR Drop Analysis

details on what?

 

[deepu539]

Re: Doubt Regarding IR Drop Analysis

As owen-li has already told, adding a power switch will make IR drop worse...So in order to reduce IR drop, please try adding decaps and if possible, increase the metal width of your always-on strap so that R decreases

 

[jirika]

Re: Doubt Regarding IR Drop Analysis

Actually, I think power gating technique will make the IR drop much worse. Coz the resistance on power switch cells is much bigger, corresponding to the power distribution network

Well you can't say this as a rule. It will help if you want switch-off some part of logic you don't need. So you'll save energy/current thus the totall current will be smaller and therefore IR will be lower.

 

[deepu539]

Re: Doubt Regarding IR Drop Analysis

Well, you will certainly save power and reduce IR by reducing number of ON cells in the circuit but you also need to assess IR Drop in a scenario where everything is ON which is the worst condition possible.
The bottomline is you dont choose power switches to resolve IR drop.

 

[jirika]

Re: Doubt Regarding IR Drop Analysis

If this condition can happend yes I agree with you.

 

[owen_li]

Re: Doubt Regarding IR Drop Analysis

yes, we should analyze the worst case when the all of the OFF domain are @ ON state to evaluate the IR drop.

 

[itsmeteja]

Re: Doubt Regarding IR Drop Analysis

Your query is little bit unclear. I am assuming that you seeing drop on vdd_aon, where as adding switches will it help reducing the static IR drop?
Definitely, it will not reduce the drop on vdd_aon but drop will reduce on the vdd_sw net assuming you have header switches (pmos gating)