A High-Performance Digital-Input Class-D Amplifier with Direct Battery Connection in a 90nm Digital CMOS Process

The class-D amplifier system presented in this paper is a second-order architecture that operates on a digital PWM input and eliminates the use of an external carrier signal. It consists of two identical audio channels and a common section consisting of a PLL and a reference system. Each channel has a digital interpolation filter followed by a digital DeltaSigma modulator, PWM generator and two second-order analog loops.