Design Of A New High Performance Current Sensing Amplifier

Nowadays,current detection technology is widely used in the feedback control signal chain of various electronic systems for system over-current protection or fault diagnosis.Especially in vehicle-mounted electronic systems that are more sensitive to current energy consumption,current detection technology has an extremely important position.Based on the actual application background,this paper proposes a specific high-side current detection technology solution according to design requirements,designs and implements a wide common-mode input range high-precision current sense amplifier（CSA）circuit with dynamic clamping.The main structure of current detection system designed in this paper includes three parts: High voltage Low Dropout Regulator（HVLDO）with cascode Miller compensation,input stage gain amplifier circuit with fully differential current sense amplifier as the core,and the output stage gain amplifier circuit with nested Miller compensation three-stage differential operational amplifier as the core.Among them,the bandgap reference module of HVLDO replaces the traditional Op amp clamp-type architecture with an output negative feedback network to ensure system reliability;The input stage circuit is based on the main structure and proposes improvement measures from the system and circuit design levels to improve the clamping accuracy of the fully differential common base current sense amplifier and further improve the detection accuracy of the system.Among them,the dynamic clamp reference auxiliary circuit is introduced into the system,and the current mirror connection method is replaced by a constant tail current connection method on the circuit.The three-stage differential Operational Amplifier in the output stage uses gain enhancement technology to ensure open-loop gain.At the same time,it introduces an improved floating voltage source push-pull output structure with low power consumption and high PSRR performance to achieve full swing output and improve Circuit transient reliability.Based on the CSMC 0.25μm BCD process,the Cadence Virtuoso EDA tool is used to design and verify the current sense amplifier circuit proposed in this article.Under the operating temperature range of-55℃～125℃ and the input detection range of ±100m V,the input common-mode range（ICMR）and power supply voltage range（PSVR）of the entire current sense amplifier system can reach 4.5V～60V,its closedloop voltage gain is 60V/V,and the detection accuracy is less than 0.65%、the input offset voltage is less than 60μV、the common mode rejection ratio（CMRR）and the Power Supply rejection ratio（PSRR）are both greater than 100 d B 、 power consumption current,input bias current,and leakage current are less than 150μA,15μA,500 n A,respectively.System simulation results show that the current-sense amplifier circuit designed in this paper has achieved the expected function,can meet the needs of specific application environment.