An advanced spread spectrum architecture to improve EMI emissions in Class D amplifier

With the purpose of reducing the out-of-band noise, an advanced digital spread spectrum technique used in monolithic Class D amplifiers with a lower-frequency reference signal is proposed in this paper, which improves an interference problem when radio equipment is independently designed. The peak-level of the measured out-of-band noise is 12 dB lower than that in a fixed frequency class D by control strategies utilizing pseudo random codes. The active area of the circuit is about 191*251 mum² and the maximal power consumed is only 2.8 muA.