CN100353670C

CN100353670C - Differential charge pump

Info

Publication number: CN100353670C
Application number: CNB021302839A
Authority: CN
Inventors: 徐哲祥; 陈志成
Original assignee: MediaTek Inc
Current assignee: MediaTek Inc
Priority date: 2002-08-22
Filing date: 2002-08-22
Publication date: 2007-12-05
Anticipated expiration: 2022-08-22
Also published as: CN1477788A

Abstract

A differential charge pump comprises a first current source, a second current source, a first switch, a second switch, a first inverse switch, a second inverse switch and a common mode feedback device. The common mode feedback device corrects the output current of the first current source according to the common mode voltage of the differential charge pump, so that the current output by the first current source is equal to the current output by the second current source. The present invention utilizes the characteristic that the common mode voltage of the differential charge pump is a fixed value to correct the size of the current source, and can accurately correct the output current of the differential charge pump. In addition, the invention only needs one group of charge pumps, has simpler structure and is easy to manufacture. And no matter whether the boosting signal or the buck signal exists or not, the correction is carried out at any time, so that the problem of common mode voltage drift is avoided.

Description

Differential electric charge pump

Technical field

The present invention is relevant for a kind of charge pump, and particularly relevant for a kind of correctable differential electric charge pump.

Background technology

(Phase Lock Loop PLL) is a kind of phase place of the signal that is produced and Circuits System that frequency all is fixed in a certain benchmark of making in the phase-locked loop.How to obtain low noise and quick phase-locked phase-locked loop, be the problem that make great efforts this area always.

Please refer to Fig. 1, the circuit block diagram of its represented traditional phase-locked loop 100.Phase-locked loop 100 includes a phase-frequency detector (Phase/Frequency Detector, PFD) 102, one loop filter (Loop Filter, LP) 104, one voltage-controlled oscillator (Voltage ControlledOscillator, VCO) 106 and one frequency divider (Frequency Divider) 108.Phase-frequency detector 102 receives an incoming frequency f simultaneously _IFWith a reference frequency f _Ref, and export an output signal S1 to loop filter 104 according to both phase differences.Loop filter 104 inputs to output signal S2 in the voltage-controlled oscillator 106 in order to after unwanted noise is filtered.The output frequency f that voltage-controlled oscillator 106 is exported _OFIn order to output as phase-locked loop 100, and output frequency f _OFAlso input in the frequency divider 108.The reference frequency f that frequency divider 108 is exported _RefEqual an output frequency f _OFDivided by a positive integer N.Wherein, the size of N value is by the control signal f of input frequency divider 108 _CODecision.

After phase-locked loop 100 starts, through (settle time) between a stationary phase afterwards, phase-locked loop 100 will enter phase locked state (lock state).At this moment, reference frequency f _RefWill with incoming frequency f _IFEquate, and output frequency f _OFThen equal N * f _Ref

The late-class circuit of phase-frequency detector 102 is a charge pump (charge pump).Please refer to Fig. 2, the rough schematic of its represented traditional charge pump.Charge pump 200 is by two current source I _UPWith I _DN, switch S 1, S2, S1 ' and S2 '-constitute.When switch S 1 receives the conducting (on) during (pumpup) signal fp of boosting from front stage circuits, so that charge pump 200 output ascending current i _pConducting when switch S 2 receives step-down (pump down) signal fd from front stage circuits is so that charge pump 200 output drop-out current i _dSwitch S 1 ' is anti-phase with switch S 1, and switch S 2 ' is anti-phase with switch S 2.When switch S 1 and S2 are all when opening circuit, switch S 1 ' and S2 ' conducting are to avoid current source I _UPWith I _DNSuspension joint.Wherein, boost signal fp step-down signal fd is according to reference frequency f _RefWith incoming frequency f _IFPhase difference decision.

Two current source I of charge pump in theory _UPWith I _DNThe physical characteristic of its circuit unit is identical, that is, current source I _UPSize of current of being exported and current source I _DNThe size of current of being exported can be identical.But because the error of manufacture process or the difference of component characteristic, it is unequal to make that both understand, so charge pump 200 is being received identical boost signal f- _UpWith step-down signal f _DnThe time, the size of current and inequality of output respectively.At this moment, even reference frequency f _RefWith incoming frequency f _IFPhase place identical, the phase current I of charge pump output ₀Its value can not be 0.So, make the deleterious that the phase lock circuitry signal is phase-locked.

The charge pump that can proofread and correct has a lot of forms traditionally, is that example is done further explanation at this with traditional differential electric charge pump.Please refer to Fig. 3, its represented traditional differential electric charge pump 300 schematic diagrames.Differential electric charge pump 300 comprises first charge pump 310, second charge pump 320 and common mode ultramagnifier CMP, and capacitor C is carried out the action of charge or discharge, wherein capacitor C is the prime of loop filter 104 in order to output current.First charge pump 310 comprises current source I _UP, current source I _DN1, switch S 1, S2, S1 ' and S2 ', its annexation is as shown in the figure.Switch S 1 is controlled by boost signal fp, and switch S 2 is controlled by step-down signal fd, and switch S 1 ' is respectively the anti-phase of switch S 1 and S2 with switch S 2 '.Node A is the output of first charge pump 310, and node A ' receives the first reference voltage VR1.Second charge pump 320 comprises current source I _UP2, current source I _DN2, switch S 3, S4, S3 ' and S4 ', its annexation is as shown in the figure.Switch S 4 is controlled by boost signal fp, and switch S 3 is controlled by step-down signal fd, and switch S 3 ' is respectively the anti-phase of switch S 3 and S4 with switch S 4 '.Node B is the output of second charge pump 320, Node B ' the reception first reference voltage VR1.The two ends of capacitor C are electrically connected with B with node A respectively.

When differential type charge pump 300 receives boost signal fp, switch S 1 and switch S 4 conductings, the electric current of charge pump 300 outputs is via switch S 1, node A flow through capacitor C and flow through switch S 4 and current source I _DN2, so that capacitor C is charged; When charge pump 300 receives step-down signal fd, switch S 2 and switch S 3 conductings, the electric current of charge pump 300 outputs is via switch S 3, the Node B capacitor C of flowing through, and through node A, switch S 2 and current source I _DN1, so that capacitor C is discharged.The voltage of node A and B on average is common-mode voltage (Common Mode Voltage).The voltage of common-mode feedback device common-mode feedback device CMP receiving node A and B and the second reference voltage VR2, the voltage of comparison node A and B average with the second reference voltage VR2 and output regulation signal Vf according to this, to regulate current source I _UP1With I _UP2Size.The shortcoming of differential electric charge pump comprises:

One, owing to comprise two groups of charge pumps, make circuit too complicated.

Two, can only guarantee I _UP1+ I _UP2=I _DN1+ I _DN2, can't guarantee I _UP1=I _UP2And I _DN1=I _DN2

Three, when differential type charge pump 300 when not starting for a long time, that is switch S 1, S2, S3 and S4 be all when opening circuit, capacitor C is a suspension joint, makes common-mode voltage be easy to drift.

Summary of the invention

In view of this, purpose of the present invention is providing a kind of correctable charge pump exactly.

According to purpose of the present invention, a kind of differential electric charge pump is proposed, comprise first current source, second current source, first switch, second switch, first phase-veversal switch, second phase-veversal switch and common mode ultramagnifier.First current source provides first electric current in order to the foundation conditioning signal.Second current source is in order to provide second electric current.One end of first switch is connected with first current source, and its state is conducting according to boost signal.One end of second switch and the other end of first switch are connected in a first node, and the other end is connected with second current source, and its state is conducting according to the step-down signal.One end of first phase-veversal switch is connected its state with first current source be the anti-phase of first switch.One end and first phase-veversal switch of second phase-veversal switch are connected in Section Point, and the other end is connected with second current source, and its state is the anti-phase of second switch.The common-mode feedback device is in order to the voltage of the voltage that receives reference voltage, first node and Section Point output regulation signal according to this also.The voltage of first node and the voltage of Section Point on average are common-mode voltage, and common-mode voltage should be certain value, and the common-mode feedback device is the size of characteristic adjusting current source output current according to this.

For above-mentioned purpose of the present invention, feature and advantage can be become apparent, a preferred embodiment cited below particularly, and conjunction with figs. are described in detail as follows.

Description of drawings

Fig. 1 represents the circuit block diagram of traditional phase-locked loop.

Fig. 2 represents the rough schematic of traditional charge pump.

Fig. 3 represents traditional differential electric charge pump schematic diagram.

Fig. 4 represents a kind of differential electric charge pump schematic diagram according to a preferred embodiment of the present invention.

Fig. 5 is expressed as another example of the application of the differential electric charge pump among Fig. 4.

Fig. 6 represents the differential electric charge pump schematic diagram according to another preferred embodiment of the present invention.

Fig. 7 is expressed as another example of the application of the differential electric charge pump among Fig. 6.

The drawing reference numeral explanation

102: phase-frequency detector

104: loop filter

106: voltage-controlled oscillator

108: frequency converter

200: charge pump

300,400,600: differential electric charge pump

310: the first charge pumps

320: the second charge pumps

Embodiment

Design of the present invention is to utilize the common-mode voltage of differential electric charge pump to should be the size of the characteristic of definite value with correcting current source output current.Please refer to Fig. 4, its expression is according to a kind of differential electric charge pump 400 schematic diagrames of a preferred embodiment of the present invention.Differential electric charge pump 400 comprises current source I _UP, current source I _DN, switch S 1, switch S 2, phase-veversal switch S1 ', phase-veversal switch S2 ' and common mode ultramagnifier CMP, in order to capacitor C 1 and capacitor C 2 are carried out charge or discharge.Wherein, differential electric charge pump 400 is the back level of the phase-frequency detector 102 of phase-locked loop 100, and capacitor C 1 and capacitor C 2 are the prime of loop filter 104.One end of switch S 1 and current source I _UPConnect, when receiving boost signal fp, switch S 1 conducting.One end of switch S 2 and the other end of switch S 1 are connected in node A, the other end of switch S 2 and current source I _DNConnect, when receiving step-down signal fd, switch S 2 conductings.The end of phase-veversal switch S1 ' and current source I _DNConnect, its state is the anti-phase of switch S 1.An end and the phase-veversal switch S1 ' of phase-veversal switch S2 ' are connected in Node B, the other end and current source I _DNConnect, its state is the anti-phase of switch S 2.Common-mode feedback device CMP in order to the voltage that receives reference voltage VR, node A and the voltage of Node B and according to this output regulation signal Vf with adjusting current source I _UPThe size of current of output.Wherein, the voltage of node A and Node B on average is common-mode voltage.

Referring again to Fig. 4, when charge pump 400 received boost signal fp, electric current flowed according to the dashed path among the figure, at this moment, and switch S 1 and S2 ' conducting, current source I _UPOutput current charges to capacitor C 1, simultaneously, and current source I _DNThe electric current of output is to capacitor C 2 discharges.If current source I _UPWith current source I _DNThe size of current of output equates, then the electric weight that filled of capacitor C 1 can equal the electric weight that capacitor C 2 is put, that is the voltage sum of node A and Node B is constant.If it is big that the voltage sum of node A and Node B becomes, represent charge volume greater than discharge capacity, just current source I _UPThe electric current of output is greater than current source I _DNOutput electric current, so common-mode feedback device CMP promptly according to this output regulation signal Vf so that current source I _UPThe electric current of output diminishes; If the voltage sum of node A and Node B diminishes, represent discharge capacity greater than charge volume, just current source I _UPThe electric current of output is less than current source I _DNOutput electric current, so common-mode feedback device CMP promptly according to this output regulation signal Vf so that current source I _UPThe electrorheological of output is big.Same reason when charge pump 400 receives step-down signal fd, also can make current source I according to identical principle _UPWith I _DNThe electric current of output is kept identical size.In addition, when charge pump 400 receives boost signal fp and step-down signal fd simultaneously, or charge pump 400 is not when receiving boost signal fp and step-down signal fd simultaneously, corrective action of the present invention all can normal operation, so no matter the combination of boost signal fp and step-down signal fd why, the corrective action of current source is all carrying out at any time, no matter and the combination of boost signal fp and step-down signal fd why, current source I _UPWith I _DNNeither is suspension joint.

Please refer to Fig. 5, it is expressed as another example of the application of the differential electric charge pump 400 among Fig. 4, and itself and Fig. 4 represent different being in replacing capacitor C 1 and C2 with capacitor C 3.When receiving boost signal, switch S 1 and switch S 2 ' conducting, electric current flows to Node B from node A, so that capacitor C 3 is charged; When receiving the step-down signal, electric current flows to node A from Node B, so that capacitor C 3 is discharged.And common-mode feedback device CMP promptly according to the voltage sum at capacitor C 3 two ends and reference voltage VR and output regulation signal Vf with correcting current source I _UPSize.

The embodiment of Fig. 4 and Fig. 5 is with correcting current source I _UPBe target, however can also correcting current source I _DNBe target, its practice and the above embodiments are similar, only need to change the conditioning signal Vf of common-mode feedback device CMP output into feed-in current source I _DN, and on average change current source I according to the voltage of node A and Node B _DNSize get final product.Please refer to Fig. 6, its represented differential electric charge pump 600 schematic diagrames according to another preferred embodiment of the present invention.Different being in the conditioning signal of common-mode feedback device CMP output of the differential electric charge pump 400 among differential electric charge pump 600 and Fig. 4 is fed into current source I _DNRather than current source I _UPWhen the voltage sum of node A and Node B during greater than reference voltage VR, conditioning signal is in order to make current source I _DNThe electrorheological of output is big, and when the voltage sum of the voltage of this node A and Node B during less than reference voltage VR, conditioning signal Vf is in order to make current source I _DNThe electric current of output diminishes.Please refer to Fig. 7, it is expressed as another example of the application of the differential electric charge pump 600 among Fig. 6, and itself and Fig. 6 represent different being in replacing capacitor C 1 and C2 with capacitor C 3.When receiving boost signal, switch S 1 and switch S 2 ' conducting, electric current flows to Node B from node A, so that capacitor C 3 is charged; When receiving the step-down signal, electric current flows to node A from Node B, so that capacitor C 3 is discharged.And common-mode feedback device CMP promptly according to the voltage sum at capacitor C 3 two ends and reference voltage VR and output regulation signal Vf with correcting current source I _DNSize.

The application of differential electric charge pump of the present invention is very wide, and the above embodiments are example to be applied to the phase-locked loop, so are not limited to this.

The invention effect

The advantage of the disclosed differential electric charge pump of the above embodiment of the present invention is as follows:

One, the present invention utilizes the common-mode voltage of differential electric charge pump to should be the size of the characteristic of definite value with the correcting current source, can proofread and correct the output current of differential electric charge pump accurately.

Two, the present invention only needs one group of charge pump, and structure is more simple and be easy to manufacturing.

No matter three have or not boost signal or step-down signal, all proofreading and correct at any time, therefore do not have the problem of common-mode voltage drift.

In sum; though the present invention with a preferred embodiment openly as above; right its is not in order to limit the present invention; any those skilled in the art; under the situation that does not break away from design of the present invention and scope; can carry out various changes and improvement, so protection scope of the present invention is as the criterion with the accompanying Claim restricted portion.

Claims

1. A differential charge pump, comprising:

a first current source, used for providing a first current according to an adjustment signal;

a second current source for providing a second current;

a first switch, wherein one end of the first switch is connected to the first current source, and the state of the first switch is conduction according to the presence of a boost signal for conduction;

A second switch, wherein one end of the second switch is connected to a first node with the other end of the first switch, and the other end of the second switch is connected to the second current source, wherein the state of the second switch depends on 1. Conduction due to the appearance of a step-down signal for conduction;

a first inversion switch, wherein one end of the first inversion switch is connected to the first current source, and the state of the first inversion switch is the inversion of the first switch;

A second inverting switch, wherein one end of the second inverting switch is connected to a second node with the first inverting switch, and the other end of the second inverting switch is connected to the second current source, wherein the first the state of the second inverting switch is the inverse of the second switch; and

a common mode feedback device for receiving a reference voltage, the voltage of the first node and the voltage of the second node and outputting the regulation signal accordingly;

a first capacitor, one end of the first capacitor is connected to the first node, and the other end of the first capacitor is grounded;

a second capacitor, one end of the second capacitor is connected to the second node, and the other end of the first capacitor is grounded;

Wherein, the output of the differential charge pump is obtained between the first node and the second node;

Wherein, when the step-up signal and the step-down signal appear at the same time, both the first switch and the second switch are turned on, and the common mode feedback device outputs the adjustment signal; and when the step-up signal and the step-down signal do not appear at the same time, Both the first inverting switch and the second inverting switch are turned on, and the common-mode feedback device also outputs the adjustment signal. Therefore, regardless of the combination of the state of the boost signal and the buck signal, the regulation of the first current source Always enforceable, neither the first nor the second current source is floating and prevents the common-mode voltage from drifting, and

Wherein, the common mode voltage is an average value of the first node voltage and the second node voltage.

2. The differential charge pump as claimed in claim 1, wherein the differential charge pump is used in a post stage of a phase/frequency detector in a phase-locked loop, and the first capacitor and the second capacitor are The front stage of the loop filter in the phase-locked loop.

3. The differential charge pump as claimed in claim 1, when the common-mode voltage is greater than the reference voltage, the adjustment signal is used to make the first current smaller, and when the voltage of the first node is the same as the second When the common-mode voltage of the node is lower than the reference voltage, the adjustment signal is used to increase the first current.

4. A differential charge pump, comprising:

a first current source, used to provide a first current;

a second current source, used to provide a second current according to an adjustment signal;

A second switch, wherein one end of the second switch is connected to a first node with the other end of the first switch, and the other end of the second switch is connected to the second current source, wherein the state of the second switch depends on When a step-down signal appears, it is turned on;

Wherein, the common mode voltage is the average value of the first node voltage and the second node voltage;

Wherein, when the step-up signal and the step-down signal appear at the same time, both the first switch and the second switch are turned on, and the common mode feedback device outputs the adjustment signal; and when the step-up signal and the step-down signal do not appear at the same time, Both the first inverting switch and the second inverting switch are turned on, and the common-mode feedback device also outputs the adjustment signal. Therefore, no matter what combination of states of the boost signal and the buck signal occurs, the regulation of the second current source It is always enforceable that neither the first nor the second current source is floating and prevents the common mode voltage from drifting.

5. The differential charge pump as claimed in claim 4, wherein the differential charge pump is used in a subsequent stage of a phase/frequency detector in a phase-locked loop, and the first capacitor and the second capacitor are The front stage of the loop filter in the phase-locked loop.

6. The differential charge pump as claimed in claim 4, when the common-mode voltage is greater than the reference voltage, the adjustment signal is used to increase the second current, when the voltage of the first node and the second When the sum of the voltages of the nodes is less than the reference voltage, the adjustment signal is used to make the second current smaller.