The correct level for DC-coupled applications is VCC–2V. Many of Micrel's devices include a VBB reference voltage pin; proper set-up is shown in Figure 6. LVPECL is an established high frequency differential signaling standard that requires external passive components for proper operation. For DC coupled logic, these external components bias both the LVPECL driver into conduction and terminate the associated differential transmission line. However. The main logic levels discussed in this application report are low-voltage positive/pseudo emitter-coupled logic (LVPECL), current-mode logic (CML), voltage-mode logic (VML) and low-voltage differential signaling (LVDS). Like LVDS, two pins are needed. Small signal swings prevent saturation during switching and increase operating frequency performance. The input and output voltage levels are referenced directly to. Positive ECL (ECL) is the most common ECL implementation method in today's low-voltage systems.
