Claims
- 1. A differential charge pump for use in a phase locked loop circuit, and which pump is powered by a power supply, comprising, a pulse generating circuit connected to receive increment and decrement pulses from a pulse generating source and to output said increment and decrement pulses as a differential output voltage at a differential output;
- a common mode circuit having a gain, in circuit connection with said differential output for regulating a common mode voltage on said differential output without changing the differential output voltage at said differential output;
- said common mode circuit comprising a feedback loop circuit for controlling the gain of said common mode circuit; said feedback loop circuit comprising:
- a cascode current source circuit for supplying current based on said differential output voltage.
- 2. The charge pump as defined in claim 1, wherein said cascode current source circuit includes field effect transistors.
- 3. The charge pump as defined in claim 1, wherein said common mode voltage is maintained at about one-half the voltage of the power supply.
- 4. A phase locked loop circuit comprising:
- a. a power supply node for supplying a power supply voltage to said phase locked loop circuit;
- b. a filter circuit for storing a differential voltage; said filter circuit having a plurality of filter circuit inputs;
- c. a differential charge pump in circuit communication with said plurality of filter circuit inputs and said power supply node, said differential charge pump having an output for providing a differential charge to said plurality of filter circuit inputs;
- d. a single ended charge pump in circuit communication with an oscillator circuit and said power supply node, for providing an input to said oscillator;
- e. a common mode circuit in circuit communication with said filter circuit and said power supply node, for regulating a common mode voltage at said filter circuit inputs; said common mode circuit comprising a feedback loop circuit having a cascode current source circuit for supplying current based on said differential charge; and
- f. a phase/frequency detector in circuit communication with said differential charge pump and said single ended charge pump.
- 5. The phase locked loop circuit of claim 4 wherein said filter circuit comprises capacitors.
- 6. The phased locked loop circuit of claim 4 wherein said common mode voltage is maintained at half the power supply voltage.
- 7. In a phase locked loop circuit having a filter circuit for storing a differential voltage and a power supply node for supplying a power supply voltage, a common mode circuit comprising:
- a. differential voltage input nodes for receiving the differential voltage;
- b. a sensing circuit in circuit communication with said differential voltage input nodes, for sensing the differential voltage on said differential voltage input nodes;
- c. a sourcing circuit in circuit communication with said differential voltage input nodes, for supplying charge to said filter circuit by said differential voltage input nodes; and
- d. a feedback loop circuit in circuit communication with said differential voltage input nodes, for controlling the amount of charge supplied to said differential voltage input nodes; said feedback loop circuit comprising:
- (1) a cascode current source circuit for supplying current based on said differential voltage input nodes voltage level.
Parent Case Info
This is a continuation of application Ser. No. 08/298,696 filed on Aug. 31, 1994.
US Referenced Citations (50)
Continuations (1)
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Number |
Date |
Country |
Parent |
298696 |
Aug 1994 |
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