一款具有快速上升时间的可均衡激光发射机

A transmitter with fast rise time and equalization

面向直接飞行时间测量的3D图像传感器应用,设计了一种具有快速上升/下降时间,输出电流脉冲可配置的阵列型VCSEL(Vertical Cavity Surface Emitting Laser)激光发射机.输出级采用直流耦合驱动电路结构,无需额外的偏置电压和分立元件;4 bit可编程均衡脉冲电路实现了不同高度或宽度的均衡电流,改善了激光驱动器输出电流的上升时间,提高了脉冲信号的完整性和飞行时间的计算精度;同时采用4 bit电流型数模转换器控制不同的输出电流,以实现不同的输出光功率;脉冲产生电路由多个延时单元、选择器和触发器构成,输出不同宽度的脉冲信号,实现了不同大小的平均电流.该电路基于CMOS 65nm工艺实现,电源电压为3.3V,后仿结果表明此发射机可以输出100~500 mA电流,在10 MHz脉冲频率时,脉冲信号实现1.09~17.38 ns可调,其上升时间为270 ps,下降时间为90 ps.均衡电路脉冲信号实现220ps~3.48ns可调,输出级最大输出电流的平均功率为0.15 W.

For the application of 3 D image sensor,a transmitter with fast rise/fall time and configurable output current pulse is proposed for array VCSEL(Vertical Cavity Surface Emitting Laser).Without extra bias voltage and discrete components,the output stage is DC coupled.A 4 bit programmable equalization circuit implements a different pulse height or width of the equalizing current,improving the rise time of the current,the integrity of the signal and accuracy of the time of flight;a 4 bit current digital-to-analog converter controls output currents to achieve different output optical power.The pulse generator is composed of delay units,selectors and triggers,outputting pulse signals of different widths,realizing different average current.The transmitter is realized with CMOS 65 nm process,and the power supply voltage is 3.3 V.The post-simulation results show that the output current can reach 100~500 mA.When the pulse frequency is 10 MHz,the pulse signal is adjustable from 1.09 to 17.38 ns whose rise time is 270 ps and fall time is 90 ps.The pulse signal of the equalization circuit can be adjusted from 220 ps~3.48 ns,and the average power of the maximum output current is 0.15 W.