CMOS magnetic field to frequency converter

Abstract

Abstract-In this paper, a CMOS magnetic field to frequency converter with high resolution is presented. It is composed of two voltage-controlled ring oscillators whose output frequency differences linearly vary with the magnetic field perpendicular to the chip surface. The prototype circuit has been fabricated in a 0.5-m CMOS process and operated at a 5-V supply voltage. The measured sensitivity is 24 kHz/mT and the power consumption is 5.1 mW. The small equivalent resolution of at least 20 T can be achieved. The frequency offset is 42 kHz when no magnetic field applied. Its nonlinearity within 120 mT is smaller than 0.56%.Index Terms-C 2 MOS, Magnetic MOSFET (MAGFET), magnetooperational amplifier (MOP), magnetically controlled oscillator (MCO).