Apparatus to decrease the spurs level in a phase-locked loop

• US 20030038661A1
• Filed: 07/26/2002
• Published: 02/27/2003
• Est. Priority Date: 07/27/2001
• Status: Abandoned Application

• Current Assignee: Valence Semiconductor, Inc.
• Original Assignee: Valence Semiconductor, Inc.
• Inventors: Behbahani, Farbod, Conta, Matteo, Chokkalingam, Ramesh
• Application Number:
  US10/207,007
• Publication Number:
  US 20030038661A1
• Time in Patent Office: Days
• US Class Current: 327/157
• CPC Class Codes: H03L 7/0895 Details of the current generators H03L7/0893 takes precedence
• CPC Class Codes: H03L 7/18 using a frequency divider or counter in the loop H03L7/20, H03L7/22 take precedence

Abstract

A charge pump is disclosed including an output capacitive element to store an output voltage, a charging current source to charge the output capacitive element, a charging switching element to couple a first bias voltage to the charging current source in response to a charging signal, a discharging current source to discharge the output capacitive element, a discharging switching element to couple a second bias voltage to the discharging current source in response to a discharging signal, a unity gain amplifier to generate an amplifier voltage substantially equal to the output voltage, a first switching element to couple the amplifier voltage to the charging current source in response to a leakage prevention signal; and a second switching element to couple the amplifier voltage to the discharging current source in response to the leakage prevention signal.

Claims

1. A charge pump, comprising:

an output capacitive element to store an output voltage;

a charging current source to charge said output capacitive element;

a charging switching element to couple a first bias voltage to said charging current source in response to a charging signal;

a discharging current source to discharge said output capacitive element;

a discharging switching element to couple a second bias voltage to said discharging current source in response to a discharging signal;

a unity gain amplifier to generate an amplifier voltage substantially equal to said output voltage;

a first switching element to couple said amplifier voltage to said charging current source in response to a leakage prevention signal; and

a second switching element to couple said amplifier voltage to said discharging current source in response to said leakage prevention signal.

2. The charge pump of claim 1, wherein said output capacitive element comprises a capacitor.

3. The charge pump of claim 1, wherein said charging switching element comprises a field effect transistor.

4. The charge pump of claim 1, wherein said discharging switching element comprises a field effect transistor.

5. The charge pump of claim 1, wherein said first switching element comprises a pass gate.

6. The charge pump of claim 1, wherein said second switching element comprises a pass gate.

7. The charge pump of claim 1, further comprising a capacitor coupled to an output of said unity gain amplifier.

8. A method comprising:

providing an output capacitive element that stores an output voltage;

providing a charging circuit to charge said output capacitive element in response to a charging signal;

providing a discharging circuit to discharge said output capacitive element in response to a discharging signal;

removing said charging and discharging signals such that said output voltage floats; and

coupling said output voltage to a second voltage substantially equal to said output voltage in response to a leakage prevention signal.

9. The method of claim 8, wherein coupling said output voltage to a second voltage is performed by a switching element.

10. The method of claim 9, wherein said switching element comprises a pass gate.

11. The method of claim 8, further comprising generating said second voltage.

12. The method of claim 11, wherein generating said second voltage includes applying said output voltage to a unity gain amplifier.

13. A charge pump, comprising:

an output capacitive element to store an output voltage;

a first charging current source to charge said output capacitive element;

a second charging current source to charge said output capacitive element;

a charging switching element to couple a first bias voltage to said first charging current source in response to a charging signal;

a first discharging current source to discharge said output capacitive element;

a second discharging current source to discharge said output capacitive element;

a discharging switching element to couple a second bias voltage to said second discharging current source in response to a discharging signal;

a unity gain amplifier to generate an amplifier voltage substantially equal to said output voltage;

a first switching element to couple said amplifier voltage to said charging current source in response to a leakage prevention signal; and

a second switching element to couple said amplifier voltage to said discharging current source in response to said leakage prevention signal.

14. The charge pump of claim 13, wherein said output capacitive element comprises a capacitor.

15. The charge pump of claim 13, wherein said charging switching element comprises a field effect transistor.

16. The charge pump of claim 13, wherein said discharging switching element comprises a field effect transistor.

17. The charge pump of claim 13, wherein said first switching element comprises a pass gate.

18. The charge pump of claim 13, wherein said second switching element comprises a pass gate.

19. The charge pump of claim 13, further comprising a capacitor coupled to an output of said unity gain amplifier.