A synchronized self oscillating Class-D amplifier for mobile application

An integrated Class-D amplifier using a synchronized self-oscillating modulator based on a hysteresis control is presented. This new feedback topology can achieve a higher gain bandwidth product to increase linearity and power supply rejection than the fixed switching frequency solutions. The switching frequency spread can also reduce the external EMI filtering constraints. To reduce the idle consumption and radiated emissions at zero output level, a synchronization technique is presented to provide truly differential outputs. The proposed amplifier, realized in CMOS 130nm process, drives up to 1W load with 0.02% THD+N, 90% efficiency with power supply range from 2.3 to 5V. The synchronization technique reduces shows up to 75% of idle consumption.