The HI-506A, HI-507A, HI-508A and HI-509A are analogmultiplexers with active overvoltage protection. Analog inputlevels may greatly exceed either power supply withoutdamaging the device or disturbing the signal path of otherchannels. Active protection circuitry assures that signalfidelity is maintained even under fault conditions that woulddestroy other multiplexers. Analog inputs can withstandconstant 70VP-Plevels with±15V supplies. Digital inputs willalso sustain continuous faults up to 4V greater than eithersupply. In addition, signal sources are protected from shortcircuiting should multiplexer supply loss occur. Each inputpresents 1kΩ of resistance under this condition. Thesefeatures make the HI-506A, HI-507A, HI-508A and HI-509Aideal for use in systems where the analog inputs originatefrom external equipment, or separately powered circuitry. Alldevices are fabricated with 44V dielectrically isolated CMOStechnology. The HI-506A is a single 16-Channel multiplexer,the HI-507A is an 8-Channel differential multiplexer, theHI-508A is a single 8-Channel multiplexer and the HI-509A isa differential 4-Channel multiplexer. If input overvoltageprotection is not needed the HI-506/507/508/509multiplexers are recommended. For further information seeApplication Notes AN520 and AN521