1 Introduction

In order to use an LVDS driver such as the TI DS90LV011A and pair it with a Sub-LVDS receiver, a step-down resistor network must be used in order to provide the proper interface between the LVDS driver and Sub-LVDS receiver. Since an LVDS driver has a typical fixed common mode voltage output of 1.2 V and typical differential voltage swing of 350 mV, the goal of the step-down resistor network is to achieve a fixed common mode voltage of 0.9 V as well as output differential voltage swing of 150 mV. Table 1-1 shows the differences between LVDS driver output levels and Sub-LVDS receiver input levels.

There are two methods in which you could implement this step-down resistor network. The method chosen depends on whether or not your receiver has internal termination integrated into it or not. The first section will focus on the formulas and simulations in a device without internal termination, while the second portion will focus on a device that includes internal termination.