Patent ID: 7881135
Filing Date: 2011-02-01
Classification: G01R

Abstract:
1. A method of estimating a critical charge required to change a logical state of a circuit under test in an integrated circuit, comprising: setting a logical state of the circuit under test to an initial value; establishing a first voltage at a charge storage node in the integrated circuit; measuring the first voltage; selectively injecting a first charge from the charge storage node into a node of the circuit under test; determining that the logical state of the circuit under test has not changed in response to said injecting of the first charge; establishing a second voltage at the charge storage node; measuring the second voltage; selectively injecting a second charge from the charge storage node into the node of the circuit under test; determining that the logical state of the circuit under test has changed in response to said injecting of the second charge; measuring a third voltage at the charge storage node after said injecting of the second charge; and computing an amount of the second charge based on the second and third voltages.