| A filterless class D audio amplifier chip with low-EMI and high efficiency is designed in this paper. The supply voltage ranges from2.4V to5.5V when the system is in normal condition. The Pulse Width Modulation has been introduced to the amplifier c, which avoids using a LC filter. It is also possible to save PCB’s area and lower system cost. In order to produce a high performance to cater for the rising need of the cuatomers, several kinds of optimizing technique are combined together, including dual feedback loop control, spread-spectrum, zero dead time control, click-pop distortion suppression control and external clock input technology, the noises can be attenuated effectively, which enhance the output signal to noise ratio (SNR). Besides, the total harmonic distortion (THD) and power supply rejection ratio (PSRR) will be improved. Besides, thermal-overload circuit、short-circuit and under-voltage circuit are integrated mode and spread-spectrum mode. What’s more, the chip is able to work in low power shuntdown mode. The chip is simulated UMC0.6umBCD technology.In this thesis, the related knowledge of traditional linear audio power amplifier was given firstly. Then the basic theory and topology of Class D audio amplifier were stated in detail. After analyzing some system parameters and the requirements of the whole design, several kinds of mainstream system configuration of Class D audio amplifier were introduced. Afterwards, the function of the designed chip and sub-block,system configuration and design specification were illustrated. Based on the above requirements, some of the sub-circuits were designed and analyzed in detail, including the voltage reference circuit, the integrator, the clikc-pop distortion suppression control and the under-voltage lock out circuit. Based on the detailed analysis of the function and parameter, the sub-circuits were simulated with Hspice, which is proved to be appropriate. |
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