ECE 124d/256c Homework 3 Due: Wed Jan. 26, 2011 Reading: Buffer Paper, Penrose Paper (on line) Ref: Bakoglu, Elmore Problems: (Note, you may find these problems are a bit deeper than previous ones -- start earlier to size them up and describe any simplifying assumptions you make.) 1. The repeater optimization proposed by Bakoglu was based on a simple model of a driver in which the output capacitance of the driver is ignored. If the output capacitance is proportional to the driver size e.g. C out = α W for a given driver width, find a new optimal delay, size and spacing rule. 2. In the buffer paper, it is noted that inverter pairs (i.e. non-inverting buffers) seem to have better jitter behavior than do simple inverters. On the other hand, they are slower. Quantify the speed difference by finding time optimal solutions for driver sizing and spacing as follows: a. assuming minimum length, let the width of the first and second buffers be a and b respectively. Find an expression for the total delay given a,b, spacing and the wire parameters.
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