Auto Gain Control method using the current sensing amplifier to compensate the walk error of the TOF LiDAR (ICCAS 2019)

TOF(Time of flight) LiDAR obtains the timing difference of the emitted pulse to the target and returned signal. TDC(Timing discriminator) measures the timing difference with specific threshold voltage level called LED (Leading edge discriminator) method. The timing difference varies since the timing at the threshold voltage is different depending on the intensity of the returned signal. This timing error is called walk error. To compensate the walk error, CFD(Constant fraction discriminator) and ZCD(Zero crossing discriminator) methods are used. These methods utilize the peak point. However when the signal is saturated, these methods bring significant error since the peak point can't be found. It is important to prevent the signal to be saturated for high performance of distance accuracy and wide input dynamic range. Walk error compensation methods composed of current sensing circuit and MOSFET will be presented. As a result, high performance of distance accuracy is achieved with the wide input dynamic range.