The HI-549 is analog multiplexers with active overvoltage protection and guaranteed rON matching. Analog input levels may greatly exceed either power supply without damaging the device or disturbing the signal path of other channels. Active protection circuitry assures that signal fidelity is maintained even under fault conditions that would destroy other multiplexers. Analog inputs can withstand constant 70VP-P levels with ±15V supplies. Digital inputs will also sustain continuous faults up to 4V greater than either supply. In addition, signal sources are protected from short circuiting should multiplexer supply loss occur. Each input presents 1k of resistance under this condition. These features make the HI-546, HI-547, HI-548 and HI-549 ideal for use in systems where the analog inputs originate from external equipment or separately powered circuitry. All devices are fabricated with 44V Dielectrically Isolated CMOS technology. The HI-549 is a 4-Channel differential device. If input overvoltage protection is not needed.