Patents Examined by Timothy P. Callaghan
  • Patent number: 6608510
    Abstract: The present invention provides a PLL circuit, which can make convergence at a high speed and convert an IF signal into an RF signal, and a wireless mobile station with that PLL circuit. An LPF charging constant current source, a discharging constant current source and a high-speed charging constant current source are connected to an output terminal of a phase comparator with current mode output of the PLL circuit. By doing so, in the case where a convergence frequency of the PLL circuit is low, an input voltage of a VCO is increased from 0V so as to be converged by using the constant current source. Meanwhile, in the case where the convergence frequency of the PLL circuit is high, the input voltage of the PLL circuit is temporarily increased to the maximum voltage by using the constant current source. Thereafter, the input voltage is gradually dropped from the maximum voltage so as to be converged by using the constant current source.
    Type: Grant
    Filed: March 30, 2001
    Date of Patent: August 19, 2003
    Assignees: Hitachi, Ltd., TTP Com Limited
    Inventors: Taizo Yamawaki, Satoshi Tanaka, Norio Hayashi, Kazuo Watanabe, Bob Henshaw