一种高精度BJT温度传感器的设计

Design of a high accuracy BJT-based temperature sensor

基于CMOS工艺,提出并实现了一种高精度的基于双极晶体管(BJT)的温度传感器,其由模拟前端和放缩式模数转换器(Zoom ADC)构成.模拟前端由偏置电路、感温电路和数字控制电路构成.其中,在偏置电路中加入了斩波器(Chopper),并用低通滤波器滤除其纹波,降低了电路的噪声,提升了感温精度。为实现对模拟前端输出结果准确的数字化,采用了放缩式模数转换器,其融合了基于逐次逼近(SAR)的粗转换和基于Σ-Δ的细转换.首先,由5-bit SAR ADC对于模拟前端的输出进行粗量化,随后,再由Σ-ΔADC对经过粗量化后的剩余电压进行细量化.该结构能够在较低的功耗下,实现高精度和高线性度.在110 nm CMOS工艺下实现该温度传感器,以验证上述结构的有效性,芯片的面积为0.18 mm^(2).测试结果表明,该温度传感器,在3 V供电电压和-45~+85℃的温度范围内,实现了±0.25℃的转换误差,过采样率为128倍,转换时间为4 ms,电路功耗为12.3μA.

A high accuracy BJT-based temperature sensor is proposed and realized on a CMOS technology.It consists of an analog-front-end(AFE)and a zoom ADC.The AFE consists of bias circuits,a temperature sensor and digital control circuits.Chopper is applied in the front-end circuit.Ripples caused by the chopper are removed by low-pass filter.Chopper and the low-pass filter remove low frequency noises and improve accuracy of temperature sensing.To achieve precision digitization to AFE’s outputs,the zoom ADC combines including successive approximation register(SAR)coarse conversion and sigma-delta fine conversion is applied.A 5-bit SAR ADC accomplishes coarse conversion to the AFE outputs at first.Then,fine conversion is done byΣ-ΔADC to quantize the residue voltage after coarse conversion.This structure achieves high accuracy and linearity with low power.To verify the proposed design,the temperature sensor is achieved on a 110 nm CMOS,and occupies 0.18 mm^(2).It achieves inaccuracy of±0.25℃from-45℃to+85℃with conversion time of 4 ms,and the oversampling rate is 128.It draws 12.3μA from a 3 V supply.