| US 7,541,853 B2 | ||
| Spread spectrum block control apparatus and spread spectrum clock generating apparatus | ||
| Masao Nakadaira, Kanagawa (Japan) | ||
| Assigned to NEC Electronics Corporation, Kanagawa (Japan) | ||
| Filed on Mar. 13, 2007, as Appl. No. 11/717,151. | ||
| Claims priority of application No. 2006-069374 (JP), filed on Mar. 14, 2006. | ||
| Prior Publication US 2007/0217483 A1, Sep. 20, 2007 | ||
| Int. Cl. H03K 3/00 (2006.01) | ||
| U.S. Cl. 327—241 [327/279; 327/291] | 12 Claims |
| 1. A spread spectrum clock control apparatus which exercises control to supply a phase control signal to a phase interpolator
which receives an input clock signal and varies the phase of an output clock signal in accordance with the phase control signal,
and to frequency-modulate the output clock signal, the apparatus comprising:
a first counter which receives a frequency-divided clock signal, changes over from up-counting to down-counting at a predetermined
first count number, performs the up-counting and down-counting a prescribed number of times and outputs an output signal when
a predetermined prescribed count number has been counted, said first counter having a state machine for managing transition
of state;
a second counter which receives the output signal from said first counter and changes over from up-counting to down-counting
at a predetermined second count number, said second counter having a state machine for managing transition of state; and
a controller which controls said phase control signal supplied to said phase interpolator, based upon count values of said
first and second counters and state of said second counter.
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