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US 7,002,393 B2Granted
Switched capacitor circuit capable of minimizing clock feedthrough effect and having low phase noise and method thereof
AssigneeMediatek Inc.
InventorEn-Hsiang Yeh
Life of this patent
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Abstract
A switched capacitor circuit includes a capacitor; a switch element for selectively coupling a first node to a second node according to a control signal, wherein the first node is coupled to the capacitor; and a charge circuit coupled to the first node for coupling the first node to a third node and for controlling a first voltage difference across the first switch element in the off-state to be greater than a charge voltage. By ensuring the charge voltage is large enough to minimize a parasitic capacitance of the switch element, the clock feedthrough effect is eliminated, the locking period of the VCO is shortened, and the phase noise of the VCO is minimized.
Claims38
A switched capacitor circuit used in an oscillator circuit, the switched capacitor comprising:
- a capacitor;
- a first switch element for selectively coupling a first node to a second node according to a control signal, wherein the first node is coupled to the capacitor, the capacitor is further connected to an oscillation node in the oscillator circuit;
- and
- a charge circuit coupled to the first node for coupling the first node to a third node being at a first predetermined charge voltage responsive to said control signal, wherein when the first switch element is switched off, the charge circuit controls a voltage difference across the first switch element to approach a second predetermined charge voltage.
1 more element
A switched capacitor circuit comprising:
- a positive side capacitor;
- a negative side capacitor;
- a first positive side switch element for selectively coupling a first positive side node to a second node according to a control signal, wherein the first positive side node is coupled to the positive side capacitor;
- a first negative side switch element for selectively coupling a first negative side node to the second node according to the control signal, wherein the first negative side node is coupled to the negative side capacitor;
- and
- a charge circuit coupled to the first positive side node and the first negative side node for coupling the first positive side node and the first negative side node to a third node being at a first predetermined charge voltage, wherein when the first positive side switch element and the first negative side switch element are switched off, the charge circuit controls a first voltage difference across the first positive side switch element and a second voltage difference across the first negative side switch element to approach a second predetermined charge voltage.
3 more elements
A method for controlling a switched capacitor circuit, the method comprising the following steps:
- connecting a capacitor to an oscillator
- connecting said capacitor to a first switch element at a first node;
- disconnecting said first node from a second node according to a control signal utilizing second switch element, wherein the first node is coupled to the first switch;
- and
- coupling the first node to a third node being at a first predetermined charge voltage responsive to said control signal for controlling a voltage difference across the first switch element in the off-state to approach a second predetermined charge voltage.
2 more elements
A method for controlling a switched capacitor circuit, the method comprising the following steps:
- providing a positive side capacitor and a first positive side switch element;
- providing a negative side capacitor and a first negative side switch element;
- disconnecting a first positive side node and a first negative side node from the second node according to the control signal respectively utilizing the first positive side switch element and the first negative side switch element, wherein the first positive side node is coupled to the positive side capacitor and the first negative side node is coupled to the negative side capacitor;
- and
- coupling the first positive side node and the first negative side node to the third node being at a first predetermined charge voltage, such that when the first positive side switch element and the first negative side switch element are switched off, a first voltage difference across the first positive side switch element and a second voltage difference across the first negative side switch element both approach to a second predetermined charge voltage.
2 more elements
A switched capacitor circuit comprising:
- a capacitor;
- a first switch element for selectively coupling a first node to a second node according to a control signal, wherein the first node is coupled to the capacitor;
- and
- a charge circuit for coupling the first node to a third node being at a first predetermined charge voltage responsive to said control signal when the first switch element is switched off to thereby control a voltage at the first node to approach a second predetermined charge voltage when the first switch element is switched off.
1 more element
A switched capacitor circuit comprising:
- a positive side capacitor;
- a negative side capacitor;
- a first positive side switch element for selectively coupling a first positive side node to a second node according to a control signal, wherein the first positive side node is coupled to the positive side capacitor;
- a first negative side switch element for selectively coupling a first negative side node to the second node according to the control signal, wherein the first negative side node is coupled to the negative side capacitor;
- and
- a charge circuit for coupling the first positive side node and the first negative side node to a third node being at a first predetermined charge voltage to control a voltage at the first positive side node and a voltage at the second positive side node to approach a second predetermined charge voltage when the first positive side switch element and the first negative side switch element are switched off.
3 more elements
Dependencies are inferred from the claim text.