CMOS magnetic sensor analog front end circuit

Abstract

The invention discloses a CMOS magnetic sensor analog front end circuit which comprises a Hall magnetic sensor, a current rotation circuit, an amplifier, a double-sampling integrator, a comparator, avoltage and current reference source and a digital circuit. According to the CMOS magnetic sensor analog front end circuit, the use of large-area passive components is avoided, a decision threshold isadjusted in a pure number manner, the robustness is enhanced, and the function switching between a magnetic switch and a magnetic quantizer is achieved.

Description

technical field [0001] The invention belongs to the field of microelectronic design and relates to a front-end circuit of a CMOS magnetic sensor. Background technique [0002] The types of magnetic sensors are Hall magnetic sensor, ARM sensor, GRM sensor and so on. Because the Hall magnetic sensor is compatible with the CMOS process, it is easy to integrate with the circuit on a single chip, and has the advantages of low price, small size and low power consumption. However, the sensitivity of the Hall magnetic sensor is low. If it is based on a standard CMOS process, it can only induce a voltage of the order of 100uV to 1mV at a voltage of 5V or lower and a magnetic field strength of about 20G, and the offset voltage is very large. , usually ten to several tens of times higher than the useful signal. In recent years, many circuits have been studied for Hall magnetic sensors and their readout circuits, such as current rotation, chopper amplifiers, correlated double sampling...

AI Technical Summary

Problems solved by technology

However, since the offset voltage is many times larger than the useful signal, and the clock frequency of the current rotation is relatively low, the filter requires a very low bandwidth and uses a huge capacitor

As we all know, the generation of the voltage reference source uses the bandgap voltage of the device, and the generated reference voltage is also many orders of magnitude higher than the Hall voltage. It is necessary to increase the gain of a high multiple to amplify the Hall voltage to be comparable to the reference voltage. The use of a high proportion of resistors or capacitors in the amplification process also results in the use of very large devices

In addition, if the threshold needs to be adjusted when it is used as a magnetic switch, the gain of the amplifier needs to be adjusted, and the adjustment of the amplifier gain usually depends on adjusting the device ratio, which usually changes the loop parameters of the analog circuit such as the feedback coefficient and capacitive load, and increases the operation put the design difficulty, and even lead to the redesign of the op amp

Images