Research And Design On Dynamic Range Laser-driving Circuit In Gas Detection System

The gas detection system based on Tunable Diode Laser Absorption Spectroscopy(TDLAS)has a very wide range of applications in industrial and daily life.Different currents can excite tunable lasers to produce wavelength-tunable light over a range of wavelengths.Due to the different wavelengths of specific absorption peaks of different gases and the concentration of the gas to be detected,different requirements are imposed on the output current range and accuracy of the laser driving circuit.The realization scheme of the on-chip laser driver circuit with adjustable research precision,adjustable step size,and wide dynamic range is of great significance to the realization of the portable gas concentration detection system.Based on the analysis of the principle of TDLAS gas detection system,according to the requirements of the system on the drive circuit,an on-chip laser current drive circuit with a wide current dynamic range and adjustable precision is designed.The circuit consists of a digital control module and DAC of the input signal.It consists of three parts: a coarse quantification module and a fine quantification module composed of an adjustable pressure-controlled current source.First,12-bit current rudder DAC is used for signal coarse quantification to preliminarily determine the required current range.Then,the 5-bit current precision adjustable resistor in the voltage-controlled current source circuit is used for fine quantification,and finally 12-bit to 16-bit current accuracy is achieved.The 12-bit current rudder DAC uses a 4+3+5 segmented approach to design current source arrays and switch arrays to improve DAC accuracy and reduce switch-induced glitches.The voltage control current source circuit utilizes a 5 bit resistor network and a current compensation circuit on the basis of the traditional structure to achieve an increase in the current accuracy and provide an output current start value.The digital module processes the corresponding switch control signal by processing two sets of input signals.The analog circuit achieves an adjustable overall circuit current accuracy.We completed the system circuit design and simulation under the UMC110 CMOS technology.The driving circuit system designed in this paper works under the conditions of 10 MHz clock frequency and 3.3V power supply voltage.The output range of the 12-bit current steering DAC is 0-2V,and the INL of the DAC obtained by the simulation is-0.998LSB~0.0457 LSB.The DNL is-0.865LSB~0.887 LSB.The overall drive circuit can achieve a drive current range of up to 14 mA with a scan step of 256 steps.The achievable precision is 12-bit-16-bit,and the minimum step size corresponding to the highest precision is 220 nA.The overall current drive circuit layout area is approximately 1400?m×850?m.Finally,after the parameters are extracted and simulated,the result shows that the error range of the output current Id is approximately 0.4mA-1mA,which is within the acceptable range of the error.The design of the whole circuit system of the wide dynamic range laser driver circuit in the gas detection system and the simulation results verify the design theory.