Delay
& Wire Cap-Coupling
CE-653 - Introduction and
Fundamentals
18
}If we assume layers above and below are
quiet
}Can estimate Cabove and Cbelow as
lumped
}Can assume to be GND
}Effective capacitance depends on
switching of neighbors
}Capacitances changes in time: glitches
due to charge-conservation (Q=CV)
}Wire-cap often now exceeds gate-cap
therefore capacitance
variation is significant, therefore delay variation is significant
B
deltaV
Ceff(A)
MCF
Constant
Vdd
Cgnd + Cadj
1
Switching with A
0
Cgnd
0
Switching opposite A
2Vdd
Cgnd+2adj
2