US 6,294,935 B1 · Built-in-self-test circuitry for testing a phase locked loop circuit

Abstract

A built-in-self-test circuit aids in testing a phase locked loop circuit. The phased locked loop has a plurality of frequency multipliers. The built-in-self-test circuit includes a frequency divider and a multiplexer. The frequency divider has a plurality of divide-by-counters. For each frequency multiplier within the plurality of frequency multipliers there is a corresponding divide-by-counter. A ratio of a multiplier for each frequency multiplier to a divider of its corresponding divide-by-counter is a constant for all frequency multipliers and corresponding divide-by-counters. When a frequency multiplier within the plurality of frequency multipliers is selected, the multiplexer selects its corresponding divide-by-counter to produce a test output clock.

Claims15

Dependent claims

A built-in-self-test circuit for aid in testing a phase locked loop circuit having a plurality of frequency multipliers, the built-in-self-test circuit comprising:

a frequency divider having a plurality of divide-by-counters, wherein for each frequency multiplier within the plurality of frequency multipliers there is a corresponding divide-by-counter, a ratio of a multiplier for each frequency multiplier to a divider of its corresponding divide-by-counter is a constant for all frequency multipliers and corresponding divide-by-counters;
and,
a multiplexer for, when a frequency multiplier within the plurality of frequency multipliers is selected, selecting its corresponding divide-by-counter to produce a test output clock.

Dependencies are inferred from the claim text.

Built-in-self-test circuitry for testing a phase locked loop circuit

Life of this patent

Built-in-self-test circuitry for testing a phase locked loop circuit

Life of this patent

Abstract

Claims15