Semiconductor device and voltage-controlled oscillation circuit
AssigneeFujitsu Limited
InventorsHiroaki Yamanaka, Kunimitsu Kousaka, Kiyoshi Nishiwaki
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Abstract
A voltage-controlled oscillation circuit (15) includes a plurality of independent ring oscillation circuits different in the number of stages; and a selector (22) selectively outputting as a feedback clock signal (FB) an output of one of the ring oscillation circuits, so that any of the outputs of the independent ring oscillation circuits is always outputted as the feedback clock signal, which makes it possible to output the feedback clock signal keeping a proper duty ratio even when the operating speed is high, allowing arbitrary adjustment of the delay time before an input signal (DLLI) is outputted.
Claims18
A semiconductor device adjusting a delay time before an input signal is outputted after being inputted, the semiconductor device comprising:
- a phase comparing circuit comparing phases of a reference clock signal and a feedback clock signal;
- and
- an oscillation circuit outputting the feedback clock signal and a delay control signal which controls the delay time based on a result of the comparison in said phase comparing circuit,
- wherein said oscillation circuit comprises:
- a plurality of independent internal oscillation circuits with different oscillation frequencies, the oscillation frequencies being controllable based on the result of the comparison in said phase comparing circuit;
- and
- a selecting circuit selectively outputting one of outputs of the plural internal oscillation circuits as the feedback clock signal.
A semiconductor device comprising:
- a plurality of cascaded logic gates with inverted outputs;
- and
- a load capacitance circuit which is connected to output ends of said logic gates with the inverted outputs and whose load capacitance value is varied according to a control signal,
- wherein load capacitance in said load capacitance circuit is oxide film capacitance of a MOS transistor.
A voltage-controlled oscillation circuit comprising:
- a plurality of independent internal oscillation circuits with different oscillation frequencies, the oscillation frequencies being controllable according to a voltage of an externally supplied voltage signal;
- and
- a selecting circuit receiving outputs of said plural internal oscillation circuits to selectively output one of the outputs as a clock signal according to a selection signal relating to selection of the outputs.
Dependencies are inferred from the claim text.