A High-Linearity and Low-EMI Multilevel Class-D Amplifier
Huajun Zhang (TU Delft - Electronic Instrumentation)
Shoubhik Karmakar (TU Delft - Electronic Instrumentation)
Lucien Breems (NXP Semiconductors)
Quino Sandifort (NXP Semiconductors)
Marco Berkhout (Goodix Technologies)
Kofi A. Makinwa (TU Delft - Microelectronics)
Qinwen Fan (TU Delft - Electronic Instrumentation)
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Abstract
This article presents a Class-D audio amplifier for automotive applications. Low electromagnetic interference (EMI) and, hence, smaller LC filter size are obtained by employing a fully differential multilevel output stage switching at 4.2 MHz. A modulation scheme with minimal switching activity at zero input reduces idle power, which is further assisted by a gate-charge reuse scheme. It also achieves high linearity due to the high loop gain realized by a third-order feedback loop with a bandwidth of 800 kHz. The prototype, fabricated in a 180-nm high-voltage BCD process, achieves a minimum THD+N of -107.8 dB/-102 dB and a peak efficiency of 91%/87% with 8- and 4-Ω loads, respectively, while drawing 7-mA quiescent current from a 14.4-V supply. The prototype meets the CISPR 25 Class 5 EMI standard with a 5.7-dB margin using an LC filter with a cutoff frequency of 580 kHz.