A transmitter with fast rise time and equalization

For the application of 3D 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 4bit 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 4bit 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 220ps~3.48ns, and the average power of the maximum output current is 0.15W.