Design and Evaluation of a USB Isolator for Medical Instrumentation

Design of medical equipment (ME) has benefitted from the use of personal computers (PCs). In order to integrate both technologies, important factors must be considered in the design of medical instrumentation, such as magnitude parameters and frequency range. Electrical protection is a fundamental characteristic in all MEs to guarantee electrical safety for both operator and patient. This paper describes the design and electrical considerations necessary to achieve galvanic isolation between ME and PC, through an isolated universal serial bus interface (IUSBI), an excellent alternative for achieving connectivity with different types of MEs and to guarantee the appropriate electric safety, according to the International Standard IEC 60601-1. The IUSBI integrates isolation technologies (energy and data transfer) into a printed circuit board (PCB), made of flamed-retardant # 4 (FR4) epoxy, with a 6.8 mm gap for air clearance and creepage distance capable of supporting a high-potential test of 3000 V ac with 125 V rms of working voltage, which provides the interface with a reinforced insulation.