Circuits for improving the reliablity of antifuses in integrated circuits

Abstract

A circuit improves the reliability of antifuses in certain types of systems by substantially eliminating the continuous undesirable applications of voltages across antifuse terminals. To accomplish this, an antifuse has applied across its two terminals a 'reading' or 'evaluation' voltage as required by the system operation for a single read or evaluation clock period (typically 5 ns to 30 ns in duration). The signal describing the state of the antifuse is then stored in a latch, register, or other suitable structure for subsequent sampling. In this manner, a low read current flows in the antifuse in response to the standard chip operating voltage for only a short period of time such as a single clock cycle. Thus, continuous voltages across the two terminals of the antifuse are avoided and an unprogrammed antifuse is not inadvertently programmed and a programmed antifuse is not inadvertently converted back to its high impedance state (i.e. 'unprogrammed'). In another embodiment, a multiplexer coupled to a terminal of the antifuse switches the terminal of the antifuse to a programming voltage node when the antifuse is selected for programming and to a reference voltage source when the antifuse is not selected for programming. The multiplexer prevents undesired voltages from being applied across the antifuse while other antifuses are being programmed. The two embodiments discussed may be used in conjunction with each other or separately.