一种采用嵌套斩波技术的Σ-Δ调制器的设计

The Design of Nested-Chopper Σ-Δ Modulator

针对MEMS传感器输出电压小并且频率低的特点,设计了一种低噪声嵌套斩波Σ-Δ调制器。该调制器采用单环积分器级联前馈(CIFF)结构与嵌套斩波技术结合,降低了传感器接口电路的低频噪声,并减小了CMOS电路中斩波开关引入的残余失调电压。仿真结果表明,提出的嵌套调制器可以有效抑制低频噪声。采用嵌套斩波Σ-Δ调制设计,在100 Hz信号带宽内,调制器最高信噪比达到109 dB,即17.8 bits的有效位数,满足了MEMS传感器低频微弱信号检测的要求。

A low-noise sigma-delta （ ∑-△ ） modulator, which uses nested-chopper technique, is designed for MEMS sensor with low-frequency weak output voltage. The proposed modulator combines cascade integrators feed forward （CIFF） architecture with nested-chopper technique. The inherent low frequency noise in the sensor interface is elim- inated, and the residual offset introduced by CMOS chopper switches is also reduced. Simulation results show that the nested-chopper ∑-△ modulator presented can restrain the low-frequency noise. The nested-chopper∑-△ modulator achieves a peak signal-to-noise ratio of 109 dB over a bandwidth of 100 Hz, equaling to a resolution of 17.8 bits, satisfying the requirement of MEMS sensor with low-frequency weak output voltage.