Patent ID: 6016332
Filing Date: 2000-01-18
Classification: H03K,H03L

Abstract:
An apparatus comprising:an analog phase-locked loop circuit having an output terminal, said analog phase-locked loop circuit including:a phase detector circuit coupled to said output terminal, and operable to detect a phase relationship between a reference signal and a signal at said output terminal, and to output charge pump control information representative of the phase relationship;a loop filter circuit which includes a charge-storing capacitor;a charge pump circuit coupled to said phase detector circuit and said loop filter circuit, said charge pump circuit being responsive to the charge pump control information from said phase detector circuit and being operable to respectively increase and decrease a charge on said capacitor when the charge pump control information indicates that one of the reference signal and the signal at said output terminal respectively has a phase lead and a phase lag with respect to the other thereof;a voltage regulator circuit responsive to said loop filter circuit and operable to output first and second oscillator control voltages; anda voltage controlled oscillator circuit responsive to the first and second oscillator control voltages from said voltage regulator circuit and having an output which is coupled to said output terminal of said phase-locked loop circuit, said voltage controlled oscillator circuit being operable to produce at said output thereof an oscillator output signal having a frequency which varies as a function of each of the first and second oscillator control voltages, wherein said voltage controlled oscillator circuit includes:a voltage to current converter section operable to output current-based frequency control information in response to said first and second oscillator control voltages; andan oscillator section operable to generate the oscillator output signal and to vary the frequency of the oscillator output signal in response to the frequency control information from said voltage to current converter section;wherein said voltage to current converter section has first and second outputs and has first and second inputs to which are respectively applied the first and second oscillator control voltages, said voltage to current converter section being operable to generate current-based first and second frequency control signals at said first and second outputs thereof, the frequency control information including the first and second frequency control signals; andwherein said voltage to current converter section includes a first resistor coupled between said first input and said first output, a second resistor coupled between said second input and said first output, a first diode having an anode coupled to said first output and a cathode coupled to ground, a second diode having an anode coupled to said second input and a cathode coupled to said second output, and a transistor coupled between said second output and ground, said transistor having a control input coupled to said first output.