Sierra Wireless, Inc.
PROTECTION CIRCUIT INVOLVING POSITIVE TEMPERATURE COEFFICIENT DEVICE

Abstract:

An electronic protection circuit includes a resettable fuse such as a positive temperature coefficient (PTC) thermistor or polymer PTC device. The resettable fuse enters a high-resistance tripped state in response to an overcurrent condition. One or more electrically controllable switches are placed in series with the resettable fuse. A monitoring and control circuit monitors voltage across the resettable fuse and to opens the switches when the voltage is outside of a predetermined range. The switches can remain open after the overcurrent event is resolved in order to allow the resettable fuse time to reset.