Design Of A Motor Driver Chip For Sweeping Machine

With the widespread application of smart power integrated circuits,motor drive chips,as an important field,are widely used in industries,automobiles,and consumer electronics in daily life.Currently,supply of chips is greatly affected by the international environment.Therefore,it is of great significance to research and design motor drive circuits.A4950 is a motor driver chip from American company,which is mainly used to drive brushed DC motors.This chip can works at a power supply voltage of 8V～40V and can continuously output a current of 3.5A.The chip’s maximum quiescent current is 10μA.According to different external input voltage,it can realize the starting,braking and speed regulation of the motor,the control of the output current,and three current decay modes of fast,slow and mixed decay.In this thesis,based on CSMC 0.25μm 60 V BCD process,the driver chip for DC brushed motors is designed,especially suitable for the motor drive and control of sweepers.The chip integrated bandgap reference,low offset operational amplifier,charge pump,oscillator,three protection circuits(over temperature,overcurrent and under voltage protection circuits),high side and low side driving circuit,etc.During the research period,the author participated in the design and simulation part of the circuit,layout planning and finally carried out the test.This chip simulates through HSPICE software.At typical condition,the simulation results show that the maximum static current is 17.6μA,the input logic level meets the requirement,and the function of decay modes is correct.Under the typical condition of the bandgap reference,the temperature coefficient is 13.3ppm/℃,the line regulation is60.1μV/V,and the PSRR is-87.1d B.Under different models,the maximum overcurrent protection current value is 5.067 A,and the minimum is 4.839 A.Under various combinations of input voltage(8V～40V)and temperature(-40℃,25℃ and 125℃),the maximum and minimum values are 5.046 A and 4.918 A.The simulation results show that the overcurrent protection circuit varies with PVT very little.The input offset voltage of the low offset operational amplifier has a system offset of 127.1μV and a standard deviation of892.9μV.At typical model,low frequency gain of the feedback amplifier is 92.7d B,the phase margin is 73.4°,and the PSRR is 68 d B,which meet the design requirement.According to the drawing rules of the layout,the layout is completed.Finally,test some chips on the PCB.The test results are consistent with the simulation results.