Voltage-clamped integrated circuit

An integrated circuit for use in an automotive environment, having a node for connection to an external vOltage, and comprising:

• a pnp bypass transistor having a base electrode, an emitter electrode coupled to the external voltage node and a collector electrode for connection to a datum potential;
• a resistor coupled between the external voltage node and the base electrode of the transistor;
• at least one Zener diode coupled between the base electrode of the transistor and a node for connection to the datum potential for enabling the bypass transistor when the voltage at the node exceeds a predetermined value, whereby the voltage at the external voltage node is clamped to a voltage no greater than the predetermined value;
• and
• a fuse connected between the external voltage node and the emitter electrode of the bypass transistor means so as to provide a subsequently identifiable cause of failure if the fuse becomes blown due to excess voltage while allowing subsequent operation of the integrated circuit if the clamp means fails but another part of the integrated circuit remains functional.

An integrated circuit for use in an automotive environment, having a node for connection to an external voltage, and comprising:

• a pnp diode-connected transistor having an emitter electrode coupled to the external voltage node, and a base electrode and a collector electrode connected together;
• at least one Zener diode coupled between a node for connection to a datum potential and the base and collector electrodes of the diode-connected transistor for conducting current from the external voltage node when the voltage at the external voltage node exceeds a predetermined value, whereby the voltage at the external voltage node is clamped to a voltage no greater than the predetermined value;
• and
• a fuse connected between the external voltage node and the emitter electrode of the diode-connected transistor so as to provide a subsequently identifiable cause of failure if the fuse becomes blown due to excess voltage while allowing subsequent operation of the integrated circuit if the clamp means fails but another part of the integrated circuit remains functional.