Research Anddesign Of Sigma-Delta ADC Applied Foraudio Device

Sigma-delta ADCs can achieve high resolution transformationbased on oversampling technology, noise shaping technology and digital filtering technology. For the actual demand of AUDIO CODEC IP program design, this work is devoted to the realization of a 14 bit Sigma-delta ADC, which consists of sigma-delta modulator and digital filter, applied for audio devices.For the modulator of Sigma-delta ADC, 2-order 1bit CIFB structure, whose over sampling ratio(OSR) is 256 times, was adopted. Beginning from the design specification, the NTF of modulator are obtained, circuit level noise and non-ideal factor effects are also taken into account with a Simulink model. For digital filtering part, three level finite impulse response(FIR)decimation filters, which are CIC/HBF1/HBF2 in sequence, are used. The simulink models are implemented by Verilog HDL after behavioral simulation finished.The high-precise modulator is realized by employing switched-capacitor in HLMC 55 nm technology. In the modulator circuit design, switches of integrator sunder special control for reducing the capacitance area; Two-stage operational amplifier,two phase non-overlapping clock circuit, dynamic latch comparator are proposed; Bandgap voltage reference circuit with the high-order compensationwas adopted and realized TC=4.87ppm/℃. The test result of the modulator, whichcan reach 84.1dB(13.67 bits) resolution, meet the design requirement.