| Nowadays,portable devices have become an indispensable part of people’s life.Due to the trend of equipment function diversification,the integration and complexity of chips in portable devices are greatly improved,which make more and more applications begin to pay attention to current energy consumption for over-current protection or fault diagnosis.Among them,high-precision current detection integrated circuit has become an important means.Therefore,based on the current shunt detection technology,this paper designs a current detection integrated circuit with current reading circuit(CR),controllable gain amplifier(PGA)and Delta-Sigma modulator.Among them,the common mode rejection ratio(CMRR)of CR is more than125 d B by using three-stage amplifier and current feedback instrument amplifier structure,and Miller nested capacitor compensation technology is used to make the amplifier have enough phase margin and work stably.By using the chopper circuit of amplifier input stage and intermediate stage,the simulation results show that the equivalent input noise is 22.7n V/√Hz when the 1/f noise angle is 3 m Hz,and the equivalent input offset voltage is 5μV.At the same time,the continuous time AC coupling ripple suppression loop is used in the CR to reduce the chopper circuit ripple.PGA adopts the structure of instrument amplifier based on double operational amplifiers,which can achieve high-precision current reading and within 1% of the output error,the gain range of CR output voltage is 1-80 times to achieve the full range input of the modulator.Delta-sigma modulator uses single loop,single bit and feedforward structure to realize digital conversion of PGA analog output voltage.The simulation results show that the noise level of delta sigma modulator is lower than-110 d B when the input frequency range is 0～1k Hz.Finally,using digital decimation filter realize digital readout.The integrated circuit is designed and simulated in SMIC 0.18μm CMOS process.The simulation results show that the circuit can detect the change range of 5m A～160m A,and the circuit error is less than 2%,and the overall power consumption is4.5m A.In a word,this design has the characteristics of high precision and adjustable gain,which has a broad market prospect. |
