A micromachined pressure sensitive switch is described, which uses an array of switch contacts on an etched silicon diaphragm. Each contact, which shorts against a common electrode at a slightly different pressure, has a miniature fuse in its path. All contacts are connected in parallel. Fine-trimming of the setpoint can be done electrically by blowing the fuses in series with contacts that close at pressures below the target setpoint. To increase the power handling of the pressure switch and protect it from over-voltage, an interface IC has been developed. This circuit is combined with one or two pressure switches to form a two-terminal device which can operate in 'normally-on' or 'normally-off' mode. © 1990.
