difference between power rail and power stripe

[owen_li]

Hi everyone.

Can you tell me the difference between power rail and power stripe?

which layer does the power rail locate ?

Thanks very much!

 

[dkpang]

Usually cells are placed with power and ground rails (metal1) connected.
power and ground stripes are the power building network which hook up power and ground from the lower layer (including the power and ground rails from metal1) to the uppermost power and ground layer.

 

[owen_li]

Do you mean metal1 power and ground are not power stripes ?
We can see the std cells all have power and ground pins.
Do you mean the power rail are connected by std cells's power and ground pins ?

Thanks!

 

[dkpang]

Power rails are laid out systematically in the floorplan where standard cells can be placed on "site" with power and ground connected to the rails. You may find the site info in the def and the power rail information in the special net section.

I would consider metal1 power and ground are rail but not stripes.

Added after 8 minutes:

put it this way...
after the IR drop analysis we may find out that we need more power in a particular area on the dice, we may add power stripes with higher metal layer connected to that area. Metal1 rails are preserved to power up the std cells only.

 

[randyest]

Eh, it's a semantic terminology thing that not everyone uses the same way.

To me, power rails are usually horizontal METAL1 grids that connects directly to each standard cell's VDD and GND pins.

Power stripes are the METAL2 - METALX (upper layer) larger, fatter, higher-pitch (bigger spacing) power grid metal parts that connect to the M1 stripes and then connect to top level for flip-chip or mid-level for IO power connections.

But I've heard many people who use the terms differently, or even interchangeably.

I think it's always best to interrupt and ask: "what exactly do you mean? What metal layer? Horizontal or vertical? Width? Pitch? etc."

The only dumb question is the one you don't ask

Cheers!