The ICS85357-11 is a 4:1 or 2:1, Crystal Oscillator-to-3.3V LVPECL / ECL Multiplexer and HiPerClockSTM is a member of the HiPerClockSTM family of High Performance Clock Solutions from ICS. The ICS85357-11 has 4 selectable crystal inputs. The device can support 10MHz - 25MHz parallel resonant crystals by connecting external capacitors between XTALIN/XTALOUT and ground. The select pins have internal pulldown resistors and leaving one input unconnected (pulled to logic low by the internal resistor) will transform the device into a 2:1 multiplexer. The SEL1 lead is the most significant line and the binary number applied to the select pins will select the same numbered data input (i.e., 00 selects XTALIN0/XTALOUT0).