Design Of Analog Front End Of Magnetic Card Signal Receiving System Based On Adaptive Mechanism

In the integrated circuit industry,tens of thousands of digital-analog hybrid chips are used in the field of personal financial terminals every year.Although affected by the EMV migration effect,financial cards are showing a gradual transition from magnetic stripe cards to IC cards,but magnetic stripe cards will still occupy a place in the financial card market for a long time.This article designs a magnetic stripe card analog front-end circuit based on an adaptive mechanism.It realizes the effective recognition of the magnetic head swiping signal,and completes the adaptive signal adjustment in a relatively fast time for correct decoding.In order to improve the signal recognition success rate and decoding accuracy rate of the magnetic card when the power supply of the device is unstable and the magnetic card is damaged,different signal peak comparison voltages are designed in a targeted manner,and the voltage is adjusted to deal with various problems that occur when the card is swiped.The designed MFE circuit mainly includes a bias voltage generating circuit composed of a programmable reference voltage generating module and resistors,a bias current generating circuit,a programmable gain amplifier,a driving circuit and an analog-to-digital converter and a decoding comparator.Among them,PGA and ADC and amplifier digital regulator together form an automatic gain control loop.The differential signal received by the magnetic head is adjusted to the amplitude range recognized by the decoding comparator through the AGC loop,and converted into a digital signal by the decoding comparator,and then sent to the magnetic card controller.Decode according to the relevant regulations in the ISO7811 protocol.The circuit design discussed in this paper is implemented based on UMC's 55nm CMOS process.Pre-simulation and layout design and post-simulation verification for MFE circuits is performed,respectively.The simulation results show that the applicable voltage range of the entire MFE circuit is 2.7V to 3.5V,the applicable temperature range is-40? to 125?,the PGA gain supports 9 levels of programmable control,the AGC gain dynamic range is 18dB-48dB,and the gain error is within 2%,the differential signal with the amplitude range of 3mV?300mV and the corresponding frequency of 1KHz?100KHz can be amplified to 8?256 times according to the actual application environment.The dynamic power consumption of the entire MFE is less than 1.8mA,the sleep power consumption is less than 20 nA,and the set up time of the adaptive mechanism is within 60ns.The paper also carried out the final digital-analog simulation and finished product testing after tapeout,and verified and analyzed the practicability and compatibility of the design based on the simulation test.Through simulation analysis,it is found that the circuit proposed in this paper has relatively portability.In addition to supporting magnetic stripe cards,it also supports IC cards.With slight modifications,it can also be used as an analog front-end circuit for weak signal detection systems in radars and other equipment.