The SY89843U is a low jitter PECL, 2:1 differential input multiplexer (MUX) optimized for redundant source switchover applications. Unlike standard multiplexers, the SY89843U unique 2:1 Runt Pulse Eliminator (RPE) MUX prevents any short cycles or "runt" pulses during switchover. In addition, a unique Fail-Safe Input protection prevents metastable conditions when the selected input clock fails to a DC voltage (voltage between the pins of the differential input drops below 100mV).The differential input includes Micrel's unique, 3-pin input termination architecture that allows customers to interface to any differential signal (AC- or DC-coupled) as small as 100mV (200mVpp) without any level shifting or termination resistor networks in the signal path. The output is 800mV, 100K compatible LVPECL with fast rise/fall times guaranteed to be less than 190ps.The SY89843U operates from a 2.5V ±5% or 3.3V ±10% supply and is guaranteed over the full industrial temperature range of -40°C to +85°C. The SY89843U is part of Micrel's high-speed, Precision Edge® product line.