Equivalent fuse circuit for a one-time programmable read-only memory array

A system for testing a one-time programmable read-only memory array, the system comprising:

• a programming voltage source that is configured to generate a programming current;
• and
• a current meter configured to measure the programming current;
• a bit line driver,
• wherein the one-time programmable read only memory array, comprising:
• a bit line coupled to the bit line driver;
• a word line;
• a memory cell coupled to the bit line driver, the memory cell comprising:
• a first transistor coupled to the word line;
• and
• a fuse equivalent circuit configured to receive the programming current and to output the programming current to the first transistor, the fuse equivalent circuit comprising:
• a voltage divider configured to divide a first voltage to generate a second voltage, wherein a first current flows through the voltage divider;
• an operational amplifier comprising:
• a first input configured to receive a third voltage;
• a second input coupled to the voltage divider;
• and an output configured to generate an output voltage;
• a current mirror coupled to:
• the bit line driver, the voltage divider and the output of the operational amplifier, wherein the current mirror is configured to receive the output voltage and configured to generate a second current;
• and
• a fuse coupled to the first transistor and to the voltage divider, wherein the fuse is configured to receive the second current, wherein the output voltage controls the second current to maintain the third voltage at substantially the same value as the second voltage.

A method for measuring a programming current of a one-time programmable read-only memory array, the method comprising:

• splitting the programming current into a first current that flows over a first current path of a fuse equivalent circuit, a second current that flows over a second current path of the fuse equivalent circuit that includes a fuse of the memory cell, and a third current that flows over a third current path of the fuse equivalent circuit;
• dividing a first voltage applied along the first path to generate a second voltage at a first node located along the first path;
• and
• generating an output voltage that controls the second current to maintain a third voltage at a second node along the second path at substantially the same value as the second voltage so that the second current has a sufficiently low value and the fuse does not burn when the second current flows through the fuse.