SWITCHING CAPACITOR GENERATION CIRCUIT

• US 20100013567A1
• Filed: 09/17/2009
• Published: 01/21/2010
• Est. Priority Date: 03/21/2007
• Status: Abandoned Application

• Current Assignee: Fujitsu Microelectronics Limited (Fujitsu Limited)
• Original Assignee: Fujitsu Microelectronics Limited (Fujitsu Limited)
• Inventors: TOMITA, Kazuhiro
• Application Number:
  US12/562,107
• Publication Number:
  US 20100013567A1
• Time in Patent Office: Days
• US Class Current: 331/117.FE
• CPC Class Codes: H03B 5/04 Modifications of generator to compensate for variations in physical values, e.g. power supply, load, temperature
• CPC Class Codes: H03H 19/004 Switched capacitor networks

Abstract

A switching capacitor generation circuit which reduces the on-resistance and parasitic capacitance of a switch element and improves the operation properties of the switch element. The switching capacitor generation circuit, which has first and second output terminals, includes a first capacitor coupled to the first output terminal, a second capacitor coupled to the second output terminal, and a single switch element coupled between the first and the second capacitors.

Claims

1. A switching capacitor generation circuit including first and second output terminals, the switching capacitor generation circuit comprising:

a first capacitor coupled to the first output terminal;

a second capacitor coupled to the second output terminal; and

a single switch element coupled between the first and the second capacitors.

2. The switching capacitor generation circuit according to claim 1, wherein the switch element includes a first N-channel MOS transistor having a source terminal and a drain terminal, the switching capacitor generation circuit further comprising:

a first bias element which biases the source terminal and drain terminal of the first N-channel MOS transistor to a low potential power supply voltage when the first N-channel MOS transistor is activated; and

a second bias element which biases the source terminal and drain terminal of the first N-channel MOS transistor to a high potential power supply voltage when the first N-channel MOS transistor is deactivated.

3. The switching capacitor generation circuit according to claim 2, wherein:

the first bias element includes a second N-channel MOS transistor;

the second bias element includes a first P-channel MOS transistor; and

the switch element and the first bias element are responsive to a common control signal.

4. The switching capacitor generation circuit according to claim 3, wherein the second bias element is further responsive to the control signal.

5. The switching capacitor generation circuit according to claim 4, further comprising:

a resistor coupled in series to the second bias element.

6. The switching capacitor generation circuit according to claim 3, further comprising:

a control voltage selection circuit which supplies a bias voltage to the second bias element to activate the second bias element in a high resistance state when the switch element and the first bias element are deactivated.

7. The switching capacitor generation circuit according to claim 6, wherein the control voltage selection circuit includes a first selector circuit which supplies the high potential power supply voltage to the second bias element when the switch element and the first bias element are activated and supplies the bias voltage to the second bias element when the switch element and the first bias element are deactivated.

8. The switching capacitor generation circuit according to claim 7, wherein the control voltage selection circuit further includes:

a transition period signal generation circuit which generates a transition period signal when the control signal falls; and

a second selector circuit which supplies the low potential power supply voltage to the second bias element using the transition period signal.

9. The switching capacitor generation circuit according to claim 8, wherein the transition period signal generation circuit includes a monostable multi-vibrator which receives the control signal.

10. The switching capacitor generation circuit according to claim 8, wherein the transition period signal generation circuit includes:

a flip-flop circuit which generates an output signal in response to the control signal; and

a delay time setting unit which delays the output signal of the flip-flop circuit and provides the flip-flop circuit with the delayed output signal as a clear signal.

11. The switching capacitor generation circuit according to claim 6, further comprising:

a bias voltage generation circuit which supplies the bias voltage to the control voltage selection circuit, wherein the bias voltage generation circuit includes;

a second P-channel MOS transistor which performs a current mirror operation with the second bias element; and

a current source which is coupled to the second P-channel MOS transistor, the bias voltage being output from a node between the second P-channel MOS transistor and the current source.

12. The switching capacitor generation circuit according to claim 6, further comprising:

a bias voltage generation circuit which supplies the bias voltage to the control voltage selection circuit, wherein the bias voltage generation circuit includes;

a second P-channel MOS transistor which performs a current mirror operation with the second bias element; and

a resistor coupled to the second P-channel MOS transistor, the bias voltage being output from a node between the second P-channel MOS transistor and the resistor.

13. The switching capacitor generation circuit according to claim 1, wherein the switch element includes a first transistor of a first conductivity type having a first terminal coupled to the first capacitor, a second terminal coupled to the second capacitor, and a first control terminal, the switching capacitor generation circuit further comprising:

a second transistor of the first conductivity type, the second transistor having a third terminal coupled to the first terminal of the first transistor, a fourth terminal coupled to a low potential power supply, and a second control terminal coupled to the first control terminal of the first transistor;

a third transistor of the first conductivity type, the third transistor having a fifth terminal coupled to the second terminal of the first transistor, a sixth terminal coupled to the low potential power supply, and a third control terminal coupled to the first control terminal of the first transistor;

a fourth transistor of a second conductivity type, the fourth transistor having a seventh terminal, an eighth terminal coupled to a high potential power supply, and a fourth control terminal coupled to the first control terminal of the first transistor;

a fifth transistor of the second conductivity type, the fifth transistor having a ninth terminal, a tenth terminal coupled to the high potential power supply, and a fifth control terminal coupled to the first control terminal of the first transistor;

a first resistor coupled between the second transistor and the fourth transistor; and

a second resistor coupled between the third transistor and the fifth transistor.

14. The switching capacitor generation circuit according to claim 1, wherein the switch element includes a first transistor of a first conductivity type having a first terminal coupled to the first capacitor, a second terminal coupled to the second capacitor, and a first control terminal, the switching capacitor generation circuit further comprising:

a second transistor of the first conductivity type, the second transistor having a third terminal coupled to the first terminal of the first transistor, a fourth terminal coupled to a low potential power supply, and a second control terminal coupled to the first control terminal of the first transistor;

a third transistor of the first conductivity type, the third transistor having a fifth terminal coupled to the second terminal of the first transistor, a sixth terminal coupled to the low potential power supply, and a third control terminal coupled to the first control terminal of the first transistor;

a fourth transistor of a second conductivity type, the fourth transistor having a seventh terminal coupled to the third terminal of the second transistor, an eighth terminal coupled to a high potential power supply, and a fourth control terminal; and

a fifth transistor of the second conductivity type, the fifth transistor having a ninth terminal coupled to the fifth terminal of the third transistor, a tenth terminal coupled to the high potential power supply, and a fifth control terminal coupled to the fourth control terminal of the fourth transistor.

15. A voltage-controlled oscillator comprising:

an LC oscillation circuit; and

a plurality of switching capacitor generation circuits coupled to the LC oscillation circuit, each of the switching capacitor generation circuits being formed by the switching capacitor generation circuit according to claim 1.

16. An LC band pass filter comprising:

an LC resonance circuit; and

a plurality of switching capacitor generation circuits coupled to the LC resonance circuit, each of the switching capacitor generation circuits being formed by the switching capacitor generation circuit according to claim 1.

17. The switching capacitor generation circuit according to claim 7, further comprising:

a bias voltage generation circuit which supplies the bias voltage to the control voltage selection circuit, wherein the bias voltage generation circuit includes;

a second P-channel MOS transistor which performs a current mirror operation with the second bias element; and

a current source which is coupled to the second P-channel MOS transistor, the bias voltage being output from a node between the second P-channel MOS transistor and the current source.

18. The switching capacitor generation circuit according to claim 8, further comprising:

a bias voltage generation circuit which supplies the bias voltage to the control voltage selection circuit, wherein the bias voltage generation circuit includes;

a second P-channel MOS transistor which performs a current mirror operation with the second bias element; and

a current source which is coupled to the second P-channel MOS transistor, the bias voltage being output from a node between the second P-channel MOS transistor and the current source.

19. The switching capacitor generation circuit according to claim 7, further comprising:

a bias voltage generation circuit which supplies the bias voltage to the control voltage selection circuit, wherein the bias voltage generation circuit includes;

a second P-channel MOS transistor which performs a current mirror operation with the second bias element; and

a resistor coupled to the second P-channel MOS transistor, the bias voltage being output from a node between the second P-channel MOS transistor and the resistor.

20. The switching capacitor generation circuit according to claim 8, further comprising:

a bias voltage generation circuit which supplies the bias voltage to the control voltage selection circuit, wherein the bias voltage generation circuit includes;

a second P-channel MOS transistor which performs a current mirror operation with the second bias element; and

a resistor coupled to the second P-channel MOS transistor, the bias voltage being output from a node between the second P-channel MOS transistor and the resistor.