Multi-site on-chip current sensor for electromigration monitoring

An on-chip current measurement method that is suitable for electromigration management is introduced. Rather than inserting a shunt in the current flow path for creating a voltage drop, the voltage drop across existing interconnects is used to determine the current flow. Current is measured with a MOSFET-only sensing circuit that provides 9 bits of resolution with midrange current levels at the threshold where electromigration concerns become relevant. This current sensor can be used for sensing currents in either VDD or VSS busses and is targeted for use in the power power/thermal management units in integrated circuits. Simulation results show the DNL/INL of this sensor is within +0.15/-0.3 LSB. The current sensor is robust to local mismatch. The small area and low power dissipation makes the structure suitable for multiple-site on-chip current measurements.