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Browse Prior Art Database

Logically Transparent Bipolar Fuse Circuit

IP.com Disclosure Number: IPCOM000102008D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 31K

Publishing Venue

IBM

Related People

Budell, TW: AUTHOR [+2]

Abstract

The disclosed bipolar fuse circuit is logically transparent while its fuse element is unblown. With the fuse element blown, the circuit's output is logically high. The fuse element is realized with a metallic-emitter npn transistor operated in the reverse mode.

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Logically Transparent Bipolar Fuse Circuit

       The disclosed bipolar fuse circuit is logically
transparent while its fuse element is unblown.  With the fuse element
blown, the circuit's output is logically high.  The fuse element is
realized with a metallic-emitter npn transistor operated in the
reverse mode.

      The circuit's input and output, IN and OUT, respectively,
switch symmetrically about voltage VR. Resistors R7 and R8, and
Schottky diode S1, regulate the voltage on node IN when the circuit
input IN is allowed to float.

      Prior to blowing fuse transistor T5, the voltage on node OUT
follows the voltage on node IN.  Fuse transistor T5 is blown by
lowering the voltage on node IN relative to node VCC, in the absence
of current limiting, in excess of the emitter-base breakdown voltage
of fuse transistor T5. Catastrophic failure of the emitter-base
junction of fuse transistor T5 results, providing a permanent
low-impedance path between node VCC and node IN.  After fuse
transistor T5 has been so blown, the voltage on node OUT will remain
fixed in the up-level state.