Hi. I need to use filler cells in a design and in specifications it is told that there should be only a capacitor between Vdd and Gnd rails. I didn't really get it. Should I connect capacitor to Vdd and Gnd rails? What kind of capacitor should I use? Also, what is the use of the capacitor?
Thanks a lot.
If you need filler cells in order to comply with the necessary layer coverage, you could use standard (or any other) cells, which you possibly could use in a redesign. In this case make sure you can access their I/Os by top metal (or at least by the 2 topmost metal layers) only.
Its not necessary to connect caps between your vdd and gnd rails in a filler cell. It is, however, advantageous because it helps eliminate noise caused by fast switching digital circuitry.