Chapter 3
Power Tomography
In this chapter, we introduce the new fast power variations estimation (power
tomography) method. The proposed power tomography is based on our paper in
ISLPED 2008 conference [62].
3.1 Preliminaries
3.1.1 Leakage current
Digital circuits are designed such that there is no direct path between the voltage
source and ground. Thus, one might expect that digital circuits do not consume
static power; however, the leakage current does occur. There are four sources of
leakage current [28] : (1) reverse-biased junctions, (2) gate-induced drain leakage,
(3) gate direct-tunneling leakage, and (4) sub-threshold leakage. Finding the
23