Self-Powered Interface Circuit for Use with a Transducer Sensor

An interface circuit for interfacing a semiconductor transducer sensor to a patient vital signs monitor is disclosed. In one embodiment, the interface circuit includes a power supply circuit that receives an excitation power signal generated by the patient monitor, and derives therefrom unregulated and regulated supply voltages for use by the electrical components on the interface circuit. Also generated by the power supply circuit is an appropriate sensor excitation signal for the semiconductor transducer. In another embodiment, the interface circuit further includes receiving circuitry for receiving a sensor output signal generated by the transducer sensor. A scaling circuit then scales that signal into a parameter signal that is proportional to the physiological condition detected by the sensor, and that is also proportional to the excitation power signal generated by the patient monitor. If necessary, the interface circuit further includes isolation circuitry, for electrically isolating the transducer sensor from the patient monitor.