10.7 LOW-POWER IIR FILTER DESIGN USING PIPELINING AND PARALLEL PROCESSING
As illustrated in Chapter 3, pipelining and parallel processing can be used to reduce the power consumption of a system by reducing the supply voltage.
Assume that the capacitance due to the multipliers is dominant and that the capacitance due to the adders can be neglected. Also, assume the supply voltage of the original system to be 5 V and the CMOS threshold voltage to be 1 V. By scattered look-ahead technique with power-of-2 decomposition, the 4-level pipelinable transfer function is given by N(z)/D(z) where
Power consumption can be reduced by using pipelining without altering the sample speed. Since the pipelined system has a shorter critical path than the original system, this smaller amount of charging capacitance can be charged or discharged during the same clock period as the original system. Therefore, the supply voltage of the pipelined system can be reduced to βV0, where β < 1 and V0 is the supply voltage of the original system. The propagation delay for the nonpipelined system is