Digital frequency control circuit, phase control circuit and PLL circuit

Digital frequency control circuit, phase control circuit and PLL circuit

  • CN 1,174,550 C
  • Filed: 08/20/1996
  • Issued: 11/03/2004
  • Est. Priority Date: 09/19/1995
  • Status: Active Grant
First Claim
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1. a digital frequency control circuit that is used for controlling in the following manner (10), promptly make the frequency (fo) of output signal (φ

  • o) of an oscillating circuit (30) level off to the frequency (fr) of a reference signal (φ

    r), the pulse period T of wherein said output signal (φ

    o) is approximately the linear function of control input value S, be T=kS+m, wherein k and m are constant, it is characterized in that described numerical frequency control circuit comprises;

    One first counter (11), connection is to receive described reference signal, to described reference signal step-by-step counting, when after described first counter has resetted, counting Nr pulse of reference signal, encourage a time end signal, resetting is to receive by the excitation in response to one first reset signal that a value related with the next one value of the Nr that equals No carries out;

    One second counter (12) connects receiving described output signal, and the step-by-step counting of described output signal so that a counting No to be provided, is resetted in 0 in response to the excitation of one second reset signal;

    One first counting circuit (13) connects to receive described counting No, calculates No-m/k as Sb;

    A register (14) connects to receive described Sb, responds a latch pulse and latchs described Sb as Sa, and Sa is provided the output as described numerical frequency control circuit (10);

    AndControl circuit (17) connects to receive described time end signal, connection is to provide described first and second reset signals and described latch pulse, encourage described latch signal in response to the excitation of described time end signal, after the excitation of described latch signal, encourage described first and second reset signals in response to the described time end signal of excitation.

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