Voltage supply droop detector

摘要

A built-in self-test (BIST) circuit for detecting power supply droops is disclosed. In one embodiment, the BIST circuit includes a transition circuit configured to launch logical signals into a delay line. The BIST circuit also includes a comparator configured to compare a logic signal based on that input into the delay line with one output from the delay line. A mismatch resulting from the comparison is indicative of a power supply droop. The BIST circuit may also include circuitry for calibrating the delay line. The calibration may be performed by enabling a feedback path between the output of the delay line and its input. Enabling the feedback path may form a ring oscillator utilizing the delay line. A counter may count the number of transitions caused by the ring oscillator in a predetermined time. The resulting count may be used to determine if the delay is in a desired range.

主权项

1. An apparatus comprising:
a delay unit coupled to receive a signal and configured to output a delayed complement of the signal; a calibration unit configured to, when operating in a first mode, determine an amount of delay provided by the delay unit; a comparison unit coupled to receive the signal and the delayed complement of the signal, wherein the comparison unit is configured to, when operating in a second mode, compare a complement of the signal to the delayed complement of the signal, and wherein the comparison unit is further configured to generate an error indication if a logic level of the complement of the signal does not match a logic level of the delayed complement of the signal; and a control unit configured to enable the calibration unit when operating in the first mode and further configured to disable the calibration unit when operating in the second mode, and wherein the control unit is further configured to adjust an amount of delay provided by the delay unit when operating in the first mode.