4-Channel Push-Pull VCSEL Drivers for HDMI Active Optical Cable in 0.18-μm CMOS

The price and power consumption of standard HDMI cables exponentially rise when the data rate increases or cable runs longer. HDMI active optical cable (AOC) can potentially solve price and power issues since fibers are tolerant to loss. However, additional optical components such as vertical-cavity surface-emitting laser (VCSEL) and photodiode (PD) are required. Therefore, drivers and transimpedance amplifiers should be designed carefully for normal operations. In this paper, two types of 4-channel VCSEL drivers for HDMI AOC are presented. The first type of the driver passes data and bias separately. It uses off-chip capacitors for AC coupling. On the other hand, the second type of the driver passes data including DC value without using off-chip capacitors. Structures of the both drivers are based on push-pull current-mode logic (CML) to achieve better power efficiency. Drivers fabricated in 0.18-μm CMOS process consume 36.5 mW/channel at 6 Gb/s and 24.7 mW/channel at 12 Gb/s, respectively.