Research And Design Of Read-Out Circuit For Multipath Wide-Bandwidth Hall Current Sensor

With the rapid development of science and technology,safe and accurate current measurement has always been the focus of attention.In modern current measurement and automation technology,magnetic sensors are one of the most important technologies.Among them,the Hall current sensor is the most widely used one.As a non-contact measurement method,the Hall current sensor does not cause a load effect,and can ensure the normal operation of the circuit under the test,and it has good compatibility with the standard CMOS processes,and low fabrication cost.Its products are widely used in automotive electronics,industrial control,aerospace and military applications.However,due to the limited sensitivity of the front-end Hall element,even advanced CMOS Hall sensors are affected by their offset voltage.The Hall voltage generated by the Hall element is very weak,as small as ?V to several mV.Therefore,it is necessary to use a high-precision instrumentation amplifier(IA)to linearly amplify it and suppress the Hall element as well as amplifier offset voltage and low-frequency 1/f noise.In addition to precision requirements,some applications(such as switched-mode power supplies)typically require a bandwidth of a few MHz to capture rapid current transients.This wide bandwidth requirement is more critical in overload/short-circuit detection.However,the state-of-the-art CMOS magnetic sensors are usually optimized for low offset or wide bandwidth,rather than both.Therefore,this paper researches and designs a multipath wide-bandwidth Hall current sensor readout circuit based on the above reasons.Firstly,this paper introduced the basic principle of Hall effect,and based on it the front-end Hall element was designed.In order to realize the separation of Hall voltage and Hall offset voltage,a four-phase spinning current technology was introduced.Based on the analysis of the instrumentation amplifier theory,the traditional capacitively coupled instrumentation amplifier(CCIA)is improved,and the dual-channel signal transmission structure is adopted to improve the overall system bandwidth.The low-frequency and high-frequency paths use the same opamp and Hall element,but only the spinning current technique and chopping technique are used in the low-frequency path.In order to solve the compromise between the residual offset and the residual ripple amplitude,the CCIA input stage transconductance is increased and the three-stage ripple reduction loop(RRL)is introduced at the same time.Compared with the traditional structure,the circuit designed in this paper can obtain low residual offset and greatly increase the system bandwidth.This design is based on SMIC 0.18?m CMOS technology,the supply voltage is 3.3V.The circuit design simulation verification and layout drawing through Cadence tools.The overall chip area is 1.36mm×1.24mm,the input-referred noise power spectral density(PSD)is 21nV/?Hz,the overall circuit-3dB bandwidth is up to 500kHz,the input-referred offset voltage of 3?V,ripple rejection ratio of 62.6dB,and the quiescent current is about 6mA(including the front-end Hall element and bias circuit),the overall circuit residual offset is less than 0.2mT.Basically meet the requirements of high-precision Hall current sensor readout circuit.This circuit is verified by design and simulation,and the tape-out is completed.