Fairchild's FSA550 4PST Depletion Mode Isolation Switch is a high-performance four-pole single-throw (4PST) normally closed Depletion-Mode isolation switch. The Depletion Mode technology allows the device to conduct signals when there is no VCC available and to isolate the signals when VCC is present. The FSA550 operates on a wide VCC range for design flexibility. Additionally, select pins allow the internal oscillator frequency to be adjusted between 500kHz and 750kHz in 75kHz steps when VCC is present. This feature is used to shift the electromagnetic interference (EMI) signature to meet customer specifications.