Design And Research Of High-precision Current Monitoring Based On Delta-Sigma ADC

Nowadays,portable devices are used widely in our lives,and their complexity and integration are greatly improved along with the enrichment of device functions.As a result,energy consumption has increasingly become an important indicator that designers pay attention to,so as to power management,current protection and fault diagnosis are carried out.Therefore,higher requirements are placed on the performance of current monitoring integrated circuits.This thesis is based on the current shunt monitoring technology,the 0.18?m BCD(Bipolar-CMOS-DMOS)technology from CMSC Technologies was used and a highprecision current monitoring circuit with high resolution and wide common-mode voltage input range which does not need controllable gain amplifier was designed in this thesis.It mainly includes submodules such as Delta-Sigma modulator,a wide common-mode voltage input circuit,and a buffer.Under the premise that not introducing a high-voltage power supply,this thesis adopts a wide common-mode voltage input circuit based on cross-coupled high-voltage switches,which can convert a clock signal with a logic electrical level of 0?3.3V into a clock signal with a logic electrical level of 30?33.3V.Therefore,the effective control of the switch is realized,and the sampling of the voltage signal with a wide common mode input range is completed.The voltage drop signal on the monitoring resistor obtained is converted into high-precision digitized one by Delta-Sigma modulator.Finally,the quantized output of the Delta-Sigma modulator is filtered through a digital filter compiled with Verilog code to obtain a converted digital signal.It can be seen that this structure can directly digitize the voltage drop signal on the high-side current monitoring resistor,avoiding the use of a high-voltage instrumentation amplifier,thereby significantly reducing the complexity of the system and the overall circuit power consumption.In this design,the Delta-Sigma modulator also uses correlated double sampling technology to achieve effective suppression of low-frequency 1/f noise and offset signals;the voltage buffer ensures the stability of the reference common-mode voltage required by each submodule circuit.The simulation results show that the current monitoring circuit designed in this thesis can realize the input common mode voltage range of 1.5?30V,the input differential range of 10?160m V,the sampling frequency of 1.6MHz,and the monitoring capability of 1?16A high current under the power supply voltage of 3.3V.Among them,at the TT process angle and room temperature of 25�C,the current monitoring gain error is 9.20%,the signal-to-noise ratio of the Delta-Sigma modulator is 92.1d B,the signal-to-noise distortion ratio is 88.6d B,the effective number of bits is 14 bit,and the bandwidth is 2.5k Hz.The overall circuit power consumption is 4.59 m W,and the total area is 1.18mm2.Compared with the thesis [55],the current monitoring circuit designed in this thesis has a wider input common-mode voltage range,and the flicker noise in the low frequency band is effectively suppressed,and the offset voltage of the operational amplifier is also significantly reduced.To sum up,the current monitoring circuit designed in this thesis has relatively good performance indicators.