Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – Fusible link or intentional destruct circuit
Reexamination Certificate
2007-05-08
2007-05-08
Tra, Quan (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
Fusible link or intentional destruct circuit
Reexamination Certificate
active
10932162
ABSTRACT:
An improved circuit for sensing and programming fuses in integrated circuits. The circuit is broadly comprised of a fuse cell, a reference circuit, a sense amplifier and a level detector. In one embodiment of the present invention, a two-stage sensing scheme is implemented. The improved fuse sensing circuit uses current-mode sensing and implements an auto-read current reduction scheme. Using a level-detect circuit, the virtual ground is raised automatically if the high-voltage power supply exceeds core supply (Vdd) by a fixed dc voltage. This reduces effective sensing voltage and the read current and thus helps preserve unblown fuse integrity. In one embodiment of the invention, four modes of operation are implemented: “Normal Read,” “Unblown_Read,” “Blown_Read_1” and “Blown_Read_2.” The default read mode is the “normal read” while the “Unblown” and “Blown” read modes are for fuse calibration purposes. In the “Unblown_Read” read mode, the circuit is operable to compare the fuse resistance against a lower reference resistance, closer to an unblown fuse resistance value, in order to make the comparison more stringent. Similarly, the “Blown_Read_1” and “Blown_Read_2” modes allow a more stringent comparison for a blown fuse resistance.
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Heald Raymond A.
Mandal Gurupada
McIntyre David Hugh
Mo William Y.
Seshadri Suresh
Darby & Darby PC
Ream M. David
Sun Microsystems Inc.
Tra Quan
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