A Power Efficient Fully Differential Back Terminated Current-Mode HDMI Source

Abstract

In this work we propose a fully differential, back terminated current-mode HDMI source with reduced power consumption. The proposed HDMI source features an asymmetrical output port. This port offers high output impedance to the outbound signal and provides back termination to the reflected signal from the line. This feature meets the output impedance requirements of a current mode source for an outbound signal and matched impedance requirement of 100Ω for the inbound reflections from the line. This completely eliminates the passive termination at the output of an HDMI source, resulting in significant saving in power. This asymmetrical impedance is completely integrated into the HDMI source, theoretically halving the power requirement while it is meeting the specifications of HDMI source, especially the differential output voltage swing and common-mode voltage levels. However, circuit topology used to realize this asymmetrical impedance requires a replica stage adding a small overhead to the overall power savings. The HDMI source is implemented in 3.3V, 0.18μm CMOS Technology which takes into account the device parasitics and second-order effects. The designed HDMI source is capable of transmitting data at the rate of 3.4 Gb/s per channel and meets all the specifications defined by HDMI Specification Version 1.4. The power consumed by this HDMI source is 45.21 mW at 3.3V for a differential output voltage swing of 1V, which is 31.5% lower than the power consumed by a conventional HDMI source.