The pinout of Texas Instruments' High Speed Interface (HSI) devices features differential signal pairs and the remaining signals comprise the supply rails, V_CC and ground, and lower speed signals such as control pins. As an example, consider a device X which is a repeater/re-driver, so both its inputs and outputs are high-speed differential signals. These guidelines can be applied to other high-speed devices such as drivers, receivers, multiplexers, and so forth. A minimum of four layers is required to accomplish a low EMI PCB design. Layer stacking should be in the following order (top-to-bottom): high-speed differential signal layer, ground plane, power plane and control signal layer.

Figure 12-1 Layer Stack