Spread spectrum clock generating apparatus

Details Spread spectrum clock generating apparatus Spread spectrum clock generating apparatus

2007-06-26

2007-06-26

Callahan, Timothy P. (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Signal converting, shaping, or generating

Clock or pulse waveform generating

C327S298000, C327S114000

Reexamination Certificate

active

11289599

ABSTRACT:
Disclosed is a spread spectrum clock generator comprising a phase interpolator, which receives a clock signal from a clock input terminal and a control signal (an up signal and/or down signal), for adjusting the phase of an output clock signal in accordance with said control signal and outputting the resultant clock signal, and a control circuit receiving and counting the clock signal that enters from the clock input terminal and outputting said control signal (up signal or down signal), which is for varying the phase of the output clock signal based upon the result of the count, to the phase interpolator. The phase of the output clock signal from the phase interpolator varies with time and the output clock signal is frequency-modulated within a prescribed frequency range. A changeover between absence and presence of a spread spectrum clock function is performed, without a sudden fluctuation in frequency, in accordance with a frequency-modulation start signal and frequency-modulation stop signal that enters from an SSC control terminal.

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M. Sugawara et al., “1.5 Gbps, 5150 ppm Spread Spectrum SerDes PHY with a 0.3 mW, 1.5 Gbps Level Detector for Serial ATA”, Symposium on VLSI Circuits Digest of Technical Paper 5-3, Jun. 2002.
S. Sidiropoulos and Mark Horowitz et al., “A semi-digital delay locked loop with unlimited phase shift capability and 0.08-400 MHz operating range,” ISSCC 1997.
M. Aoyama et al., 3 Gbps, 5000 ppm Spread Spectrum SerDes PHY with frequency tracking Phase Interpolator for Serial ATA:, Symposium on VLSI Circuits Digest of Technical Paper 8-4, Jun. 2003.

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