应用于TCXO的低功耗Sigma-Delta调制器的设计

Design of a Low-power Sigma-Delta Modulator Used in TCXO

采用CSMC0.35μm混合工艺设计了一个用于温度补偿晶体振荡器(TCXO)的二阶低功耗Sigma-Delta调制器.为减小低频温度信号带宽内的1/f噪声及失调对调制器精度的影响,采用斩波技术把1/f噪声及失调调制到有用信号带宽之外.结合Cadence Spectre及Matlab仿真结果显示,该调制器在温度信号带宽范围内的信噪声比为93.6dB,精度达到15.26位.在3V电源电压下静态功耗小于80μW,满足了该TCXO系统对调制器的低功耗及14位精度的要求.

A second-order low-power Sigma-Delta modulator used in the temperature compensated crystal oscillator（TCXO）has been designed using CSMC 0.35 μm mixed process.To reduce the effects of 1/f noise in low-frequency temperature signal bandwidth and the offset on the accuracy of the modulator,the chopper technique was applied to move the 1/f noise and offset out of the useful signal bandwidth.Simulation results using Cadence Spectre and Matlab indicate that the modulator achieves an SNR of 93.6 dB,an accuracy of 15.26 bits,and a static power dissipation of less than 80 μW under 3 V supply,meeting the low-power and 14-bit accuracy requirements of the TCXO system to the modulator.