Skewed inverter delay line for use in measuring critical paths in an integrated circuit

Abstract

An integrated circuit includes a testable delay path. A transition of a delay path input signal causes a subsequent transition of a delay path output signal. A pulse generator receives the delay path input and output signals and produces a pulse signal having a pulse width indicative of the delay between the delay path input and output signal transitions. A delay line receives the pulse signal from the pulse generator. The delay line generates information indicative of the pulse signal pulse width. The delay line may include multiple stages in series where each stage reduces the pulse width of the pulse signal. The delay line may include a high skew inverter having PMOS and NMOS transistors having significantly different gains. The pulse generator is configured to produce a positive going pulse signal regardless of whether the delay path is inverting or non-inverting.