Digital Input/Output Port for the Automotive Environment
Original Publication Date: 1988-Aug-01
Included in the Prior Art Database: 2005-Feb-15
This article describes a circuit arrangement that operates as a bidirectional input/output (I/O) port which will not be damaged by the typical automotive error and transient voltages. Also, it gives a controlling processor the ability to detect the various error states. The automotive environment requires that any I/O port that connects to the automobile wiring harness be able to be shorted to either the negative battery terminal (ground) or to the positive battery terminal (+VBAT) with no damage. The I/O port must still be functional after the error state is removed. The I/O port must also be capable of taking positive or negative voltage transients of 60 volts. The circuit disclosed herein uses a minimum of components to perform the I/O function while fully protecting the port from externally induced damage.