Sage-Tips

What is cell delay in VLSI?

Cell delay is the amount of delay from input to output of a logic gate. in a path. The values of cell delay can be got from Timing libraries (i.e., .lib ) or from SDF files if they are available. Net delay is the amount of delay from the output of a cell to the input.

What parameters does the cell delay depend on?

Delay is directly proportional to the input transition and the output load. More is the output cap, more time the cell would require to charge/discharge that capacitance. And hence, delays would be more.

Can we remove propagation delay?

Extrinsic delays may be reduced by employing new materials for metallization (e.g. Copper-Damascene technology) and even trying to integrate optical communication lines (optical transceivers on the same chip).

What is propagation delay in VLSI?

Propagation delay of a gate or cell is the time it takes for a signal at the input pin to affect the output signal at output pin. For any gate propagation delay is measured between 50\% of input transition to the corresponding 50\% of output transition.

How does VLSI calculate net delay?

Net delay is the difference between the time a signal is first applied to the net and the time it reaches other devices connected to that net. It is due to the finite resistance and capacitance of the net.

What factor affect to cell and net delay?

Delay is directly proportional to the input transition and the output load. 1. More is the output cap, more time the cell would require to charge/discharge that capacitance. And hence, delays would be more.

How can I improve my flip flop setup time?

Setup time for Flip Flop:

1. Take a clock of pulse width 10ns i.e. a frequency of 100MHz.
2. Consider data transition from 0 → 1 at infinite setup time say 10ns before the active clock edge.
3. Calculate the C-Q delay from 50\% of clock to 50\% of Output.
4. Keep on bringing the data closer to the active edge of the clock.

In which counter propagation delay will be less?

8. In synchronous counter, propagation delay is less.

How do you reduce propagation delay in CMOS?

if there’s a setup violation in the design, it implies that a combinational path has large delay than required. In this case, you need to reduce the delay by up sizing cell, which reduces resistance, in turn, reduces RC delay of the path.