A Low Power Inverter-Based Sigma-Delta ADC for Audio Applications

An inverter-based design technique is applied to accomplish a low power Sigma-Delta analog-to-digital converter (ADC) for audio applications. The Sigma-Delta modulator of the ADC adopts three order feedforward structure. The modulator is based on inverter-based switched-capacitor integrator. To increase the robust of the modulator, a constant gm bias LDO is used to regulate the inverter bias point. The Sigma-Delta modulator is implemented in SMIC 0.18 μm CMOS process. The simulation results of the Sigma-Delta modulator achieve 91.5 dB signal to noise and distortion ratio (SNDR), 96 dB dynamic range (DR) over 24 kHz audio band with 6.144 MHz sampling frequency and it consumes 0.48 mW power with 1.3 V supply voltage. The modulator is suitable for high performance and low power applications.