A time encoded decimation filter for noise shaped power DACs

Abstract

This paper presents a new approach to reduce the out of band energy in a class D amplifier driven by a DAC. The proposed architecture is based on a Time Encoded Filter (TEF). The TEF operates as a discrete time linear system on the pulse widths of a PWM signal rather than on the amplitudes of a sequence. It only requires RC circuits, comparators and digital logic. Hence, it can be integrated along with the D/A converter. The main advantage of this approach is that the number of power inductors and capacitors of the off chip low pass filter may be reduced.