6. Dynamic Logic [12 pts] Consider a non-stacked domino gate. When the keeper is

Question

6. Dynamic Logic [12 pts] Consider a non-stacked domino gate. When the keeper is sized to meet the noise margin requirements in a particular process technology, the domino gate fails to operate with more than 8 pull-down branches. Each pull-down device has the same width with different input signals. Gie s the same width with CLK AOUT .AN (a) [4 pts] Briefly explain the reason for this failure (b) [8 pts] Suppose the Vt of all PMOS and NMOS transistors in the circuit are lower than the nominal value by the same amount due to process variation. The domino gate can operate properly with smore, less,equal number of pull-down branches. Choose your answer and give a brief explanation.

Explanation / Answer

a)

Since, the inputs are in cascade. So the evaluation depends on the next stage that causes monotonicity problem.

The circuit may result in incorrect output.

b)

Since, domino circuits are more sensitive to noise than static circuit. In presence of too much noise the static circuits can restore the correct output but it is not possible in case of dynnamic gates i.e. domino dates.

lowering the threshold reduces the noise margin hence the domino gate can operate properly with more number of pull-down branches.

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