On-chip PLL phase and jitter self-test circuit

Details On-chip PLL phase and jitter self-test circuit On-chip PLL phase and jitter self-test circuit

1997-06-30

1999-03-30

Grimm, Siegfried H.

Oscillators

Automatic frequency stabilization using a phase or frequency...

Afc with logic elements

331 12, 331 14, 331 16, 331 44, 375226, 375376, H03L 706

Patent

active

058894357

ABSTRACT:
An ASIC includes a PLL and digital circuitry to quantize and measure phase and average maximum jitter between a system clock input to the PLL, and a PLL-generated clock signal. The system clock is input to a series-string of delay elements, each contributing a delay of about 1.DELTA.t. Each delay element is associated with a two-input logic element, such as an EX-OR gate or an EX-NOR gate. One input to each two-input logic element is a version of the PLL-generated clock delayed by about (N/2) .DELTA.t. The second input to the first EX-OR is the output from the first delay element, the second input to the first EX-NOR is the output from the second delay element, and so on. Whichever delay element outputs a signal most closely in phase with the delayed PLL-generated clock will have an associated two-input logic element signal with a minimum duty cycle. Each two-input logic element output signal is capacitor integrated, sampled, stored and digitized. The digitized output signal identifies the lowest duty cycle two-input logic element, and thus phase shift. The relative breadth of the integrated capacitor voltage profile provides a measure of average maximum jitter.

REFERENCES:
patent: 5381085 (1995-01-01), Fischer
patent: 5663991 (1997-09-01), Kelkar et al.

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