CN104702271B - The characteristic calibration method of phase-locked loop circuit and voltage controlled oscillator - Google Patents
The characteristic calibration method of phase-locked loop circuit and voltage controlled oscillator Download PDFInfo
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- CN104702271B CN104702271B CN201310670112.3A CN201310670112A CN104702271B CN 104702271 B CN104702271 B CN 104702271B CN 201310670112 A CN201310670112 A CN 201310670112A CN 104702271 B CN104702271 B CN 104702271B
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Abstract
A kind of characteristic calibration method of phase-locked loop circuit and voltage controlled oscillator, the phase-locked loop circuit includes phase frequency detector, charge pump, loop filter, voltage controlled oscillator and frequency divider, and the voltage controlled oscillator includes at least two voltage controlled oscillator units with different characteristics curve；The phase-locked loop circuit further includes：Frequency comparing unit, control unit, reference voltage generation unit and switch unit.The phase-locked loop circuit and the characteristic calibration method of voltage controlled oscillator that technical solution of the present invention provides can automatically select the characteristic curve of voltage controlled oscillator, promote the overall performance of phase-locked loop circuit, improve the production yield of the phase-locked loop circuit.
Description
Technical field
The present invention relates to technical field of integrated circuits, the characteristic of more particularly to a kind of phase-locked loop circuit and voltage controlled oscillator is bent
The calibration method of line.
Background technology
Phaselocked loop（PLL, Phase-locked loops）Circuit be it is a kind of using feedback control principle realize frequency and
The simultaneous techniques of phase, effect are that the output signal of circuit is synchronous with its external reference signal holding.Work as reference signal
Frequency or phase when changing, phase-locked loop circuit can detect this variation, and by its internal reponse system come
The frequency or phase of output signal are adjusted, until the two re-synchronization.When this characteristic of phase-locked loop circuit is widely used in
The generation of clock signal.
Fig. 1 is a kind of structure diagram of common phase-locked loop circuit.With reference to figure 1, the phase-locked loop circuit includes frequency discrimination
Phase discriminator（PFD, Phase Frequency Detector）11st, charge pump 12, loop filter（LPF, Loop Filter）
13rd, voltage controlled oscillator（VCO, Voltage Controlled Oscillator）14 and frequency divider 15.
The phase frequency detector 11 is adapted to detect for the phase difference of input signal Vin and fractional frequency signal Vdiv, and output and institute
State the directly proportional error voltage signal of phase difference；The charge pump 12 is suitable for the error voltage signal being converted into filling for loop
Discharge current；The loop filter 13 is adapted to filter out the radio-frequency component that the charge pump 12 exports, and inhibits voltage ripple, in institute
State output control voltage Vc under the control of charging and discharging currents；The voltage controlled oscillator 14 is suitable for generating frequency and the control voltage
Output signal Vout directly proportional Vc；The frequency divider 15 is suitable for carrying out fractional frequency division to the output signal Vout, generates institute
State fractional frequency signal Vdiv.
The frequency Fout of the output signal Vout and the relation of the control voltage Vc are as follows：Fout=F0+Kvco*Vc,
F0 is the frequency that the control voltage Vc is equal to output signal Vout when zero, also referred to as the voltage controlled oscillator 14 from
By frequency of oscillation, Kvco is the gain of the voltage controlled oscillator 14.The frequency of voltage controlled oscillator output signal and control electricity are described
The curve of relation is referred to as the characteristic curve of voltage controlled oscillator between pressure（tuning curve）, Fig. 2 shows described voltage-controlled shake
Swing the idealized characteristic C0 of device 14 and actual characteristic curve C1.
With reference to figure 2, in the ideal case, the frequency of the frequency Fout of the output signal Vout obtained will usually it is expected
The ideal voltage value V0 of value F0 and the control voltage Vc are designed in the centre of the idealized characteristic C0, i.e. point P0（V0,
F0）Positioned at the central linear area of the idealized characteristic C0, the ideal voltage value V0 of the control voltage Vc is close to described
The central value of voltage Vc is controlled, to obtain enough control reference voltages and the best section of opposite linear degree, the control electricity
The central value of pressure Vc refers to the half of the minimum amount of voltage that Vmin and the sum of maximum voltage value Vmax of the control voltage.
However, due to, there are inevitable process deviation, forming the lock phase in the phase-locked loop circuit production link
The device of loop circuit（Such as transistor, resistance, capacitance etc.）Performance can deviate its ideal performance, these deviate so that the pressure
The actual characteristic curve C1 of control oscillator 14 deviates its ideal curve C0.Therefore, it is desirable to obtain the frequency of the output signal Vout
The frequency value F 0 of rate Fout, it is described to control the actual voltage value of voltage Vc as V1, i.e. point P1（V1, F0）It deviates from described actual special
The central linear area of linearity curve C1, the actual voltage value V1 of the control voltage Vc deviate from the center of the control voltage Vc
Value.
The actual characteristic curve C1 of the voltage controlled oscillator 14, which deviates its ideal curve C0, would generally cause the phaselocked loop
The penalty of circuit, such as there is phase jitter（phase jitter）.Under extreme case, the reality of the control voltage Vc
Voltage value V1 may not be between the minimum amount of voltage that Vmin and maximum voltage value Vmax of the control voltage Vc, the phaselocked loop
Circuit can not generate required clock frequency at all, that is to say, that the controllable frequency excursion of the voltage controlled oscillator 14 by
It is compressed by process deviation.
The content of the invention
What the present invention solved is that the actual characteristic curve of voltage controlled oscillator and the offset of its idealized characteristic cause phaselocked loop
The problem of circuit performance deteriorates.
To solve the above problems, the present invention provides a kind of phase-locked loop circuit, including phase frequency detector, charge pump, loop filter
Ripple device, voltage controlled oscillator and frequency divider, the voltage controlled oscillator includes at least two, and there is the voltage-controlled of different characteristics curve to shake
Swing unit；The phase-locked loop circuit further includes：
Frequency comparing unit, suitable for the frequency of the input signal of the phase-locked loop circuit and frequency divider generation
The frequency of fractional frequency signal generates first choice letter when the frequency of the input signal is equal with the frequency of the fractional frequency signal
Number, otherwise generate the second selection signal；
Control unit, suitable for keeping the voltage controlled oscillator unit of selection work at present when receiving the first choice signal
Work selects the voltage controlled oscillator unit work of non-present work when receiving second selection signal；
Reference voltage generation unit, suitable for generating reference voltage, the reference voltage and the control of the voltage controlled oscillator unit
The central value of voltage processed is related；
Switch unit, the first input end of the switch unit connect the output terminal of the loop filter, the switch
Second input terminal of unit is suitable for receiving the reference voltage, and the output terminal of the switch unit connects the voltage controlled oscillator
Input terminal, the control terminal of the switch unit are suitable for receiving first control signal, and the first control signal is suitable for described in control
The output terminal of switch unit is connected with the first input end of the switch unit or the second input terminal with the switch unit
Connection.
The present invention also provides a kind of characteristic calibration method of voltage controlled oscillator, the voltage controlled oscillator is applied to lock
In phase loop circuit, the phase-locked loop circuit includes phase frequency detector, charge pump, loop filter, frequency divider and described voltage-controlled
Oscillator, which is characterized in that the voltage controlled oscillator includes at least two voltage controlled oscillator units with different characteristics curve, institute
Stating calibration method includes：
Disconnect the connection between the loop filter and the voltage controlled oscillator；
Apply reference voltage to the voltage controlled oscillator, the reference voltage and the control voltage of the voltage controlled oscillator unit
Central value it is related；
Select a voltage controlled oscillator unit work in described at least two voltage controlled oscillator units with different characteristics curve
Make；
Judging the frequency for the fractional frequency signal that the frequency of the input signal of the phase-locked loop circuit is generated with the frequency divider is
It is no equal；
If the frequency of the input signal is equal with the frequency of the fractional frequency signal, the voltage-controlled of selection work at present is kept
Oscillating unit works, and stops applying the reference voltage, connects the loop filter and the voltage controlled oscillator；
If the frequency of the input signal and the frequency of the fractional frequency signal differ, voltage-controlled the shaking of non-present work is selected
Swing cell operation.
Compared with prior art, technical scheme has the following advantages：
Voltage controlled oscillator in the phase-locked loop circuit that technical solution of the present invention provides, which includes at least two, has different characteristics
The voltage controlled oscillator unit of curve.When calibrating the characteristic curve of the voltage controlled oscillator, filtered by switch unit open-loop
The connection of device and the voltage controlled oscillator applies reference voltage to the voltage controlled oscillator unit, then by comparing fractional frequency signal with
Whether the frequency of input signal judges it is expected the corresponding control voltage of the frequency values of the output frequency obtained in work at present
Voltage controlled oscillator unit characteristic curve among.
If the fractional frequency signal is equal with the frequency of the input signal, represent it is expected the frequency values of the output frequency obtained
Corresponding control voltage then keeps selection work at present among the characteristic curve of the voltage controlled oscillator unit of work at present
Voltage controlled oscillator unit works, and stops applying the reference voltage to the voltage controlled oscillator, connect the loop filter and
The voltage controlled oscillator, calibration terminate；If the fractional frequency signal and the frequency of the input signal differ, represent it is expected what is obtained
The corresponding control voltage of the frequency values of output frequency is not among the characteristic curve of the voltage controlled oscillator unit of work at present, then
Another voltage controlled oscillator unit work is switched to, continues the frequency of input signal described in comparison and the fractional frequency signal.
Technical solution of the present invention by set in the voltage controlled oscillator it is multiple have the voltage-controlled of different characteristics curve shake
Swing unit, it would be desirable to which the corresponding control voltage of the frequency values of the output frequency of acquisition is located in the voltage controlled oscillation of work at present
Among the characteristic curve of unit, the phase jitter as caused by the nonlinear characteristic of the voltage controlled oscillator is reduced, improves institute
The overall performance of phase-locked loop circuit is stated, the generation yield of the phase-locked loop circuit in process of production improves.
Technical solution of the present invention is by the use of the phase-locked loop circuit input signal in itself as calibration source, without using it
The analog voltage source or analogue current sources that he is additionally influenced by factors such as technique, temperature, voltages are as calibration source, the input letter
It number is usually generated by crystal oscillator, therefore, the accuracy of calibration result is high.
Technical solution of the present invention make use of the most of circuit of the phase-locked loop circuit in itself to the voltage controlled oscillator
Characteristic curve is calibrated, and merely adds reference voltage generation unit, switch unit, frequency comparing unit and control unit,
Simple analog circuit or digital circuit may be employed in increased each unit, and calibration result is hardly by technique change shadow
It rings, while the precision of calibration result is controllable.
Due in most phase-locked loop circuits, the control voltage of charge pump current equalization point output voltage and voltage controlled oscillator
Central value be phase-locked loop circuit supply voltage half, therefore, the present invention alternative in, the reference
Voltage is the half of the supply voltage of the phase-locked loop circuit, and the selection of the reference voltage can be with align currents type charge pump
Optimum current Differential Output voltage, eliminates the reference frequency grass as caused by out-of-balance current（Reference Spur）.
In the alternative of the present invention, the reference voltage generation unit includes the equal first resistor of two resistance values and the
Two resistance, the first resistor and second resistance connect to generate the reference voltage.Due to the reference voltage generation unit
Circuit structure it is simple, therefore, the accuracy of the reference voltage is high, from process variations influence.
In the alternative of the present invention, the reference voltage generation unit further includes first switch.The first switch exists
It is closed during the characteristic curve for calibrating the voltage controlled oscillator, does not influence the generation of the reference voltage；The first switch is in school
It is disconnected after the characteristic curve of the accurate voltage controlled oscillator, no current flows through the first resistor and second resistance, therefore, subtracts
The small power consumption of the phase-locked loop circuit.
In the alternative of the present invention, described control unit includes calibration Code memory, passes through the calibration Code memory
The calibration code for stepping up or being stepped down by is exported, it can be rapidly corresponding by the frequency values for it is expected output frequency obtained
The control voltage voltage controlled oscillator unit that is located in work at present characteristic curve among.
Description of the drawings
Fig. 1 is a kind of structure diagram of common phase-locked loop circuit；
Fig. 2 is the idealized characteristic of voltage controlled oscillator shown in FIG. 1 and the schematic diagram of actual characteristic curve；
Fig. 3 is the structure diagram of the phase-locked loop circuit of embodiment of the present invention；
Fig. 4 is the schematic diagram of the actual characteristic curve of the voltage controlled oscillator unit of the embodiment of the present invention；
Fig. 5 is a kind of electrical block diagram of the frequency comparing unit of the embodiment of the present invention；
Fig. 6 is a kind of circuit diagram of the reference voltage generation unit of the embodiment of the present invention；
Fig. 7 is another circuit diagram of the reference voltage generation unit of the embodiment of the present invention；
Fig. 8 is a kind of circuit diagram of the switch unit of the embodiment of the present invention；
Fig. 9 is the flow diagram of the characteristic calibration method of the voltage controlled oscillator of embodiment of the present invention.
Specific embodiment
As described in background, since there are inevitable process deviation, locks in phase-locked loop circuit production link
The actual characteristic curve of voltage controlled oscillator in phase loop circuit and its idealized characteristic phase deviation cause the property of phase-locked loop circuit
It can deteriorate.
In order to ensure that voltage controlled oscillator there are enough controllable frequency excursions, make the frequency of the output frequency of expectation acquisition
It is worth corresponding control voltage to be located among the characteristic curve of voltage controlled oscillator, is typically increase voltage controlled oscillation in the prior art
The gain of device.But the gain increase of voltage controlled oscillator can influence the loop performance of phase-locked loop circuit, and the application of the method is simultaneously paid no attention to
Think.Technical solution of the present invention provides the characteristic calibration method of a kind of phase-locked loop circuit and voltage controlled oscillator, passes through calibration
The characteristic curve of voltage controlled oscillator can effectively promote the overall performance of phase-locked loop circuit.
It is understandable for the above objects, features and advantages of the present invention is enable to become apparent, below in conjunction with the accompanying drawings to the present invention
Specific embodiment be described in detail.
Fig. 3 is the structure diagram of the phase-locked loop circuit of embodiment of the present invention.With reference to figure 3, the phase-locked loop circuit bag
Include phase frequency detector 31, charge pump 32, loop filter 33, voltage controlled oscillator 34, frequency divider 35, frequency comparing unit 36, control
Unit 37 processed, reference voltage generation unit 38 and switch unit 39.
Specifically, the phase frequency detector 31 is adapted to detect for the frequency dividing letter that input signal Vin is generated with the frequency divider 35
The phase difference of number Vdiv is to generate the error voltage signal directly proportional to the phase difference, and the input signal Vin is usually by crystalline substance
Oscillation body device generates, and frequency is the reference frequency of the phase-locked loop circuit；The charge pump 32 is suitable for error electricity
Pressure signal is converted into the charging and discharging currents of loop；The loop filter 33 is suitable for exporting under the control of the charging and discharging currents
Control voltage；The frequency divider 35 is suitable for carrying out scaling down processing to the output signal Vout that the voltage controlled oscillator 34 generates to produce
The raw fractional frequency signal Vdiv.The phase frequency detector 31, charge pump 32, the specific electricity of loop filter 33 and frequency divider 35
Line structure and function with it is similar in the prior art, be no longer described in detail herein.
Unlike the prior art, the voltage controlled oscillator 34 includes at least two voltage controlled oscillation with different characteristics curve
Unit.Each voltage controlled oscillator unit can be independently arranged, i.e., each voltage controlled oscillator unit is not shared with other voltage controlled oscillator units
Component；It can also be formed by way of sharing component and using various combination.For example, the pressure for LC oscillator forms
Control oscillator, each oscillating unit can include an inductance and a capacitance, can also all oscillating units share an electricity
Sense and each oscillating unit use the capacitance of different capacitances, can also all oscillating units share a capacitance and each vibrate list
Member uses the inductance of different induction value.
No matter which kind of mode to set the structure of the voltage controlled oscillator unit using, the control voltage of each voltage controlled oscillator unit
Input terminal is connected, i.e., all voltage controlled oscillator units receive identical control voltage.The voltage controlled oscillator unit can be that LC vibrates
The oscillator of device, ring oscillator or other forms, the invention is not limited in this regard.
In embodiments of the present invention, illustrated by taking four voltage controlled oscillator units as an example, Fig. 4 show described four it is voltage-controlled
The schematic diagram of the actual characteristic curve of oscillating unit.With reference to figure 4, abscissa represents the control voltage Vc of the voltage controlled oscillator unit
（That is, the control voltage of the voltage controlled oscillator 34）, the output signal of the ordinate expression voltage controlled oscillator unit（It is i.e. described
Export signal Vout）Frequency Fout, curve C11, curve C12, curve C13 and curve C14 represent respectively it is described four pressure
The actual characteristic curve of oscillating unit is controlled, Vmin and Vmax represent the minimum amount of voltage that of the control voltage Vc and maximum electricity respectively
Pressure value.
The frequency comparing unit 36 is suitable for the frequency of the input signal Vin and the frequency of the fractional frequency signal Vdiv
Rate generates first choice signal when the frequency of the input signal Vin is equal with the frequency of the fractional frequency signal Vdiv, in institute
It states the frequency of input signal Vin and whens frequency of the fractional frequency signal Vdiv does not wait generates the second selection signal.The present invention is implemented
Example provides a kind of particular circuit configurations of the frequency comparing unit 36, as shown in Figure 5.
With reference to figure 5, the frequency comparing unit 36 includes the first counter unit 51, the second counter unit 52 and number
It is worth comparing unit 53.First counter unit 51 is suitable for the pulse number of the input signal Vin is counted to produce
Raw first numerical value of N 1；Second counter unit 52 is suitable for the pulse number of the fractional frequency signal Vdiv is counted to produce
Raw second value N2；The numerical value comparing unit 53 is suitable for first numerical value of N 1 and the second value N2, described
First numerical value of N 1 generates the first choice signal when equal with the second value N2, in first numerical value of N 1 and described
Two numerical value of N 2 generate second selection signal whens not waiting.
Specifically, any one counting in first counter unit 51 and second counter unit 52 is chosen
As reference, first counter unit 51 and second counter unit 52 start simultaneously at counting to unit, when as ginseng
When the pulse number that the counting unit examined receives reaches predetermined value, another counting unit stops counting.
The numerical value comparing unit 53 is to determine that first numerical value of N 1 and the second value N2 are by difference operation
It is no equal, it is contemplated that the numerical value comparing unit 53 is there are error, if first numerical value of N 1 and the difference of the second value N2
Absolute value in certain error range, that is, exist | N1-N2 | during≤A, the numerical value comparing unit 53 still exports described first
Selection signal, A are error.The error A can be according to the characteristic required precision to calibrating the voltage controlled oscillator 34
It is configured, higher to the characteristic required precision of the calibration voltage controlled oscillator 34, the value of the error A is smaller.
Described control unit 37 is suitable for selection the voltage-controlled of work at present is kept to shake when receiving the first choice signal
Cell operation is swung, the voltage controlled oscillator unit work of non-present work is selected when receiving second selection signal.Specifically,
Enable Pin can be set to each voltage controlled oscillator unit, and described control unit 37 is suitable for four unlike signals of output respectively as control
Make the enable signal of four voltage controlled oscillator units work.Certainly, described control unit 37 can also use other modes control
The voltage controlled oscillator unit work is made, this is not limited by the present invention.
In embodiments of the present invention, described control unit 37 includes being suitable for the calibration code deposit of at least two calibration codes of storage
Device, the calibration code are corresponded with the voltage controlled oscillator unit, and the calibration code control of the calibration Code memory output corresponds to
Voltage controlled oscillator unit work.Specifically, the storage bit number of the calibration Code memory is according to the number of the voltage controlled oscillator
It determines：2n>=m, n are the storage bit number of the calibration Code memory, and m is the number of the voltage controlled oscillator.The embodiment of the present invention
In, the voltage controlled oscillator 34 includes four voltage controlled oscillator units, and therefore, the storage bit number of the calibration Code memory can be
Two, the calibration code of storage is respectively 00,01,10 and 11.
By taking the calibration code 00,01,10 and 11 corresponds to characteristic curve as C11, C12, C13 and C14 respectively as an example, if
The calibration Code memory output calibration code 00 then has the voltage controlled oscillation of characteristic curve C11 in the voltage controlled oscillator unit 34
Cell operation；If the calibration Code memory output calibration code 01, there is characteristic curve C12 in the voltage controlled oscillator unit 34
Voltage controlled oscillator unit work；If the calibration Code memory output calibration code 10, have in the voltage controlled oscillator unit 34
The voltage controlled oscillator unit work of characteristic curve C13；If the calibration Code memory output calibration code 11, the voltage controlled oscillation list
The voltage controlled oscillator unit with characteristic curve C14 works in member 34.
The calibration Code memory is suitable for preserving the calibration code currently exported when receiving the first choice signal,
The calibration code output of non-present output is selected when receiving second selection signal.Specifically, in the frequency comparing unit
During the 36 output first choice signal, the frequency of the input signal Vin and the frequency phase of the fractional frequency signal Vdiv are represented
Deng the calibration code that currently exports of calibration Code memory preservation controls the voltage controlled oscillator unit of work at present to work on；
When the frequency comparing unit 36 exports second selection signal, the frequency of the input signal Vin and described point are represented
The frequency of frequency signal Vdiv differs, the calibration code output of the calibration Code memory selection non-present output controls the pressure
It controls oscillator 34 and switches the work of another voltage controlled oscillator unit.
It further, can be in different ways when the frequency comparing unit 36 exports second selection signal
Select the calibration code output of non-present output.If for example, the calibration Code memory exports minimum calibration code 00 in advance, i.e., in advance
It works setting in the voltage controlled oscillator unit of the characteristic curve C11 of bottom, described second is exported in the frequency comparing unit 36
During selection signal, the calibration code that the calibration Code memory selection steps up exports；If the calibration Code memory is defeated in advance
Go out maximum calibration code 11, i.e., the voltage controlled oscillator unit work of the preset characteristic curve C14 positioned at the top, in the frequency ratio
When exporting second selection signal compared with unit 36, the calibration code that the calibration Code memory selection is stepped down by exports；If institute
State the calibration code 01 that calibration Code memory exports median in advance（Or 10）, i.e., it is preset to be located at intermediate characteristic curve C12（Or
C13）Voltage controlled oscillator unit work, second selection signal can include the 3rd selection signal and the 4th selection signal：
When the frequency of the input signal Vin is more than the frequency of the fractional frequency signal Vdiv, the frequency comparing unit 36 generates described
3rd selection signal, the calibration code output that the calibration Code memory selection steps up；In the frequency of the input signal Vin
During frequency less than the fractional frequency signal Vdiv, the frequency comparing unit 36 generates the 4th selection signal, the calibration
The calibration code output that Code memory selection is stepped down by.
It should be noted that the circuit structure of described control unit 37 is not limited to calibration code provided in an embodiment of the present invention
Register can also use the circuit structure of other forms, and this is not limited by the present invention.
The reference voltage generation unit 38 is suitable for generating reference voltage, the reference voltage and the voltage controlled oscillator unit
Control voltage central value it is related.Due in most phase-locked loop circuits, charge pump current equalization point output voltage and voltage-controlled
The central value of the control voltage of oscillator is the half of the supply voltage of phase-locked loop circuit, therefore, is implemented in the present invention
In example, the half for the supply voltage that the reference voltage is the phase-locked loop circuit is set, and the selection of the reference voltage can
With align currents type charge pump optimum current Differential Output voltage, the reference frequency grass as caused by out-of-balance current is eliminated.
The embodiment of the present invention provides a kind of particular circuit configurations of the reference voltage generation unit 38, as shown in Figure 6.
With reference to figure 6, the reference voltage generation unit 38 includes first resistor R1 and second resistance R2, the first resistor
The resistance value of R1 and second resistance R2 are equal.Specifically, one end of the first resistor R1 is suitable for inputting the phase-locked loop circuit
The other end of supply voltage Vdd, the first resistor R1 connect one end of the second resistance R2 and suitable for exporting the ginseng
Voltage is examined, the other end of the second resistance R2 is suitable for ground connection.
In embodiments of the present invention, since the reference voltage generation unit 38 is using the circuit knot of simple electric resistance partial pressure
Structure generates the reference voltage, and therefore, the accuracy of the reference voltage is high, from process variations influence.
The embodiment of the present invention also provides the particular circuit configurations of another reference voltage generation unit 38, such as Fig. 7 institutes
Show.With reference to figure 7, the reference voltage generation unit 38 includes first switch K1 and the equal first resistor R1 of resistance value and the
Two resistance R2.Specifically, one end of the first resistor R1 is suitable for inputting the supply voltage Vdd of the phase-locked loop circuit, described
The other end of first resistor R1 connects one end of the second resistance R2 and suitable for exporting the reference voltage, the second resistance
The other end of R2 is grounded by the first switch K1, i.e., the first end of described first switch K1 connects the second resistance R2's
The other end, the second end ground connection of the first switch K1.The control terminal of the first switch K1 is suitable for receiving second control signal,
The second control signal controls the first switch K1 before the frequency comparing unit 36 generates the first choice signal
It is closed, the reference voltage generation unit 38 is generated described with reference to electricity by the first resistor R1 and second resistance R2 partial pressures
Pressure；The second control signal controls the first switch after the frequency comparing unit 36 generates the first choice signal
K1 is disconnected, and no current flows through the first resistor R1 and second resistance R2, can reduce the power consumption of the phase-locked loop circuit.Cause
This, the second control signal is related to the first choice signal.
The output terminal of the first input end D1 connections loop filter 33 of the switch unit 39, the switch unit
39 the second input terminal D2 is suitable for receiving the reference voltage, the output terminal D3 connections voltage controlled oscillation of the switch unit 39
The input terminal of device 34（That is, the input terminal of the voltage controlled oscillator unit）, the control terminal D4 of the switch unit 39 is suitable for receiving the
One control signal, the first control signal are suitable for the output terminal D3 for controlling the switch unit 39 and the switch unit 39
First input end D1 connections are connected with the second input terminal D2 of the switch unit 39.
Specifically, the first control signal can include the 3rd control signal and the 4th control signal.3rd control
Signal processed is suitable for the output terminal D3 of the switch unit 39 is controlled to be connected with the first input end D1 of the switch unit；Described
Four control signals are suitable for the output terminal D3 of the switch unit 39 is controlled to be connected with the second input D2 ends of the switch unit 39.
3rd control signal and the 4th control signal are related to the first choice signal respectively：3rd control signal
It is generated after the frequency comparing unit 36 generates the first choice signal, the 4th control signal compares in the frequency
Unit 36 generates before generating the first choice signal.
The embodiment of the present invention provides a kind of particular circuit configurations of the switch unit 39, as shown in Figure 8.With reference to figure 8, institute
Stating the control terminal of switch unit 39 includes the first control terminal D5 and the second control terminal D6, the first control terminal D5 suitable for receiving institute
The 3rd control signal is stated, the second control terminal D6 is suitable for receiving the 4th control signal.The switch unit 39 includes the
Two first ends for switching the switches of K2 and the 3rd K3, the second switch K2 are the first input end D1 of the switch unit 39, institute
State the first end of second end connection the 3rd switch K3 of second switch K2 and as the output terminal D3 of the switch unit 39,
The control terminal of the second switch K2 is the first control terminal D5；The first end of the 3rd switch K3 is the switch unit
39 the second input terminal D2, the control terminal of the 3rd switch K3 is the 3rd control terminal D6.
It should be noted that the switch unit 39 or single-pole double-throw switch (SPDT), the public affairs of the single-pole double-throw switch (SPDT)
End is the output terminal D3 of the switch unit 39 altogether, and the first end of the single-pole double-throw switch (SPDT) is the first of the switch unit 39
Input terminal D1, the second end of the single-pole double-throw switch (SPDT) are the second input terminal D2 of the switch unit 39, the single-pole double throw
The control terminal of switch is the control terminal D4 of the switch unit 39.
The phase-locked loop circuit that technical solution of the present invention provides, the loop filter 33 is disconnected by the switch unit 39
With the connection of the voltage controlled oscillator 34, apply the reference voltage to the voltage controlled oscillator 34, the reference voltage according to
The central value of the control voltage of the voltage controlled oscillator 34 is set.By comparing the fractional frequency signal Vdiv frequency with it is described defeated
Enter the frequency of signal Vin, can judge it is expected that whether the corresponding control voltage of the frequency values of the output frequency obtained is working as
Among the characteristic curve of the voltage controlled oscillator unit of preceding work.
With reference to figure 3 and Fig. 4, exemplified by it is expected that the frequency value F 0 of output frequency of acquisition is located at characteristic curve C13, tie below
Attached drawing is closed to illustrate the operation principle of the phase-locked loop circuit of the present invention.
After phase-locked loop circuit startup, the output terminal D3 of the switch unit 39 is controlled by the first control signal
It is connected with the second input terminal D2 of the switch unit 39, i.e., described switch unit 39 produces the reference voltage generation unit 38
Raw reference voltage output is to the voltage controlled oscillator 34；
Any one voltage controlled oscillator unit work in the voltage controlled oscillator 34 is pre-set, in the present embodiment, in advance
Put with characteristic curve C12 voltage controlled oscillator unit work, i.e., by described control unit 37 calibration Code memory output with
The corresponding calibration code 01 of voltage controlled oscillator unit with characteristic curve C12；
The frequency divider 35 divides the output signal Vout that the voltage controlled oscillator 34 generates, and generates fractional frequency signal
Vdiv；
The frequency of the 36 input signal Vin of frequency comparing unit and the frequency of the fractional frequency signal Vdiv,
With reference to figure 4, when it is the reference voltage Vref to control voltage, the output frequency of each voltage controlled oscillator unit is point P11, point respectively
P12, point P13 and the corresponding ordinate values of point P14, since the ordinate value of point P12 is less than the ordinate value F0 of point P13, table
Show the corresponding control voltage of frequency value F 0 of the output frequency for it is expected to obtain not in the voltage controlled oscillator unit of work at present
Among characteristic curve, therefore, the frequency comparing unit 36 generates the second selection signal；
After described control unit 37 receives second selection signal, it is incremented by upwards by the calibration Code memory output
Calibration code 10, control with characteristic curve C13 voltage controlled oscillator unit work；
The frequency comparing unit 36 continues the frequency of the frequency of input signal Vin described in comparison and the fractional frequency signal Vdiv
Rate, the ordinate value due to point P13 represent it is expected the output frequency obtained it is expected the frequency value F 0 of the output frequency obtained
The corresponding control voltage of frequency value F 0 is among the characteristic curve of the voltage controlled oscillator unit of work at present, therefore, the frequency
Rate comparing unit 36 generates first choice signal；
After the frequency comparing unit 36 generates the first choice signal, opened described in the first control signal control
The output terminal D3 for closing unit 39 is connected with the first input end D1 of the switch unit 39, and the loop of the phase-locked loop circuit closes
It closes.
Technical solution of the present invention is multiple voltage-controlled with different characteristics curve by being set in the voltage controlled oscillator 34
The corresponding control voltage of the frequency value F 0 for it is expected output frequency obtained can be located in work at present by oscillating unit
Among the characteristic curve of voltage controlled oscillator unit, reduce the phase jitter as caused by the nonlinear characteristic of the voltage controlled oscillator 34,
Improve the overall performance of the phase-locked loop circuit.
Since technical solution of the present invention is by the use of the phase-locked loop circuit input signal Vin in itself as calibration source, and do not have
There are the analog voltage source additionally influenced using other by factors such as technique, temperature, voltages or analogue current sources as calibration source, institute
It states input signal Vin usually to be generated by crystal oscillator, therefore, the accuracy of calibration result is high.
Technical solution of the present invention make use of the most of circuit of the phase-locked loop circuit in itself to the voltage controlled oscillator 34
Characteristic curve calibrated, merely add the reference voltage generation unit 38, switch unit 39, frequency comparing unit 36 with
And control unit 37, if the embodiment of the present invention is described, simple analog circuit or number may be employed in increased each unit
Word circuit realizes that calibration result is hardly by process variations influence, while the precision of calibration result is controllable.
Further, described control unit 37 includes calibration Code memory, passes through the upward step of calibration Code memory output
Into or the calibration code that is stepped down by, the corresponding control electricity of the frequency value F 0 that will rapidly can it is expected the output frequency obtained
Among the characteristic curve for pressing the voltage controlled oscillator unit for being located in work at present.
Technical solution of the present invention also provides a kind of characteristic calibration method of voltage controlled oscillator, the voltage controlled oscillator
Applied in phase-locked loop circuit, the phase-locked loop circuit include phase frequency detector, charge pump, loop filter, frequency divider and
The voltage controlled oscillator, the voltage controlled oscillator include at least two voltage controlled oscillator units with different characteristics curve.
Fig. 9 is the flow diagram of the characteristic calibration method of the voltage controlled oscillator of embodiment of the present invention, reference
Fig. 9, the calibration method include：
Step S11：Disconnect the connection between the loop filter and the voltage controlled oscillator；
Step S12：Apply reference voltage to the voltage controlled oscillator；
The reference voltage is related to the central value of the control voltage of the voltage controlled oscillator unit；
Step S13：One in described at least two voltage controlled oscillator units with different characteristics curve is selected voltage-controlled to shake
Swing cell operation；
Step S14：Judge the fractional frequency signal that the frequency of the input signal of the phase-locked loop circuit is generated with the frequency divider
Frequency it is whether equal；
If the frequency of the input signal is equal with the frequency of the fractional frequency signal, step S15 is performed：Selection is kept to work as
The voltage controlled oscillator unit work of preceding work, and stops applying the reference voltage, connects the loop filter and described voltage-controlled
Oscillator；
If the frequency of the input signal and the frequency of the fractional frequency signal differ, step S16 is performed：Select non-present
The voltage controlled oscillator unit work of work.
Step S14 is performed again.
In conclusion the phase-locked loop circuit of technical solution of the present invention offer and the characteristic calibration side of voltage controlled oscillator
Method can automatically select the characteristic curve of voltage controlled oscillator, rapidly that the frequency values for it is expected output frequency obtained are right with it
Among the characteristic curve for the voltage controlled oscillator unit that the control voltage answered is located in work at present, reduce by the voltage controlled oscillator
Phase jitter caused by nonlinear characteristic, the overall performance of phase-locked loop circuit are promoted.
Although present disclosure is as above, present invention is not limited to this.Any those skilled in the art are not departing from this
It in the spirit and scope of invention, can make various changes or modifications, therefore protection scope of the present invention should be with claim institute
Subject to the scope of restriction.
Claims (12)
1. a kind of phase-locked loop circuit, including phase frequency detector, charge pump, loop filter, voltage controlled oscillator and frequency divider,
It is characterized in that, the voltage controlled oscillator, including at least two for given idealized characteristic has different characteristics curve
Voltage controlled oscillator unit；The phase-locked loop circuit further includes：
Frequency comparing unit, suitable for the frequency of the input signal of the phase-locked loop circuit and the frequency dividing of frequency divider generation
The frequency of signal generates first choice signal when the frequency of the input signal is equal with the frequency of the fractional frequency signal, no
Then generate the second selection signal；
Control unit, suitable for keeping the voltage controlled oscillator unit work of selection work at present when receiving the first choice signal
Make, the voltage controlled oscillator unit work of non-present work is selected when receiving second selection signal；
Reference voltage generation unit, suitable for generating reference voltage, the reference voltage and the control electricity of the voltage controlled oscillator unit
The central value of pressure is related；
Switch unit, the first input end of the switch unit connect the output terminal of the loop filter, the switch unit
The second input terminal be suitable for receiving the reference voltage, the output terminal of the switch unit connects the input of the voltage controlled oscillator
End, the control terminal of the switch unit are suitable for receiving first control signal, and the first control signal is suitable for controlling the switch
The output terminal of unit is connected with the first input end of the switch unit or is connected with the second input terminal of the switch unit.
2. phase-locked loop circuit as described in claim 1, which is characterized in that the frequency comparing unit includes：First counter
Unit is counted to generate the first numerical value suitable for the pulse number to the input signal；
Second counter unit is counted to generate second value suitable for the pulse number to the fractional frequency signal；
Numerical value comparing unit, suitable for first numerical value and second value, in first numerical value and the second value
The first choice signal is generated when equal, second selection is generated when first numerical value and the second value do not wait
Signal.
3. phase-locked loop circuit as described in claim 1, which is characterized in that second selection signal includes the 3rd selection signal
With the 4th selection signal；
The frequency comparing unit is suitable for when the frequency of the input signal is more than the frequency of the fractional frequency signal described in generation
3rd selection signal generates the 4th selection letter when the frequency of the input signal is less than the frequency of the fractional frequency signal
Number；
Described control unit include be suitable for storage at least two calibration codes calibration Code memory, the calibration code with it is described voltage-controlled
Oscillating unit corresponds, and the calibration code of the calibration Code memory output controls corresponding voltage controlled oscillator unit work, and fits
The calibration code currently exported is preserved when the first choice signal is being received, is selected when receiving three selection signal
The calibration code output stepped up is selected, the calibration code output being stepped down by is selected when receiving four selection signal.
4. phase-locked loop circuit as described in claim 1, which is characterized in that described control unit includes being suitable for storage at least two
The calibration Code memory of calibration code, the calibration code are corresponded with the voltage controlled oscillator unit, and the calibration Code memory is defeated
The calibration code gone out controls corresponding voltage controlled oscillator unit work, and current suitable for being preserved when receiving the first choice signal
The calibration code of output selects the calibration code output of non-present output when receiving second selection signal.
5. phase-locked loop circuit as described in claim 1, which is characterized in that the reference voltage is the electricity of the phase-locked loop circuit
The half of source voltage.
6. phase-locked loop circuit as claimed in claim 5, which is characterized in that the reference voltage generation unit includes resistance value phase
Deng first resistor and second resistance；
One end of the first resistor is suitable for inputting the supply voltage, other end connection second electricity of the first resistor
One end of resistance simultaneously is suitable for exporting the reference voltage, and the other end of the second resistance is suitable for ground connection.
7. phase-locked loop circuit as claimed in claim 6, which is characterized in that the reference voltage generation unit further includes first and opens
It closes, the other end of the second resistance is grounded by the first switch；
The first end of the first switch connects the other end of the second resistance, the second end ground connection of the first switch, institute
The control terminal for stating first switch is suitable for receiving second control signal, the second control signal and the first choice signal phase
It closes.
8. phase-locked loop circuit as described in claim 1, which is characterized in that the first control signal includes the 3rd control signal
With the 4th control signal；
3rd control signal is suitable for the output terminal of the switch unit is controlled with the first input end of the switch unit to connect
It connects；
4th control signal is suitable for the output terminal of the switch unit is controlled with the second input terminal of the switch unit to connect
It connects.
9. phase-locked loop circuit as claimed in claim 8, which is characterized in that the 3rd control signal and the 4th control signal point
It is not related to the first choice signal.
10. phase-locked loop circuit as claimed in claim 9, which is characterized in that the control terminal of the switch unit includes the first control
End processed and the second control terminal, first control terminal are suitable for receiving the 3rd control signal, and second control terminal is suitable for connecing
Receive the 4th control signal；
The switch unit includes second switch and the 3rd switch；
The first end of the second switch is the first input end of the switch unit, and the second end of the second switch connects institute
State the first end of the 3rd switch and as the output terminal of the switch unit, the control terminal of the second switch is the described first control
End processed；
The first end of 3rd switch is the second input terminal of the switch unit, and the control terminal of the 3rd switch is the 3rd
Control terminal.
11. phase-locked loop circuit as described in claim 1, which is characterized in that the switch unit is single-pole double-throw switch (SPDT), described
The common port of single-pole double-throw switch (SPDT) is the output terminal of the switch unit, and the first end of the single-pole double-throw switch (SPDT) is the switch
The first input end of unit, the second end of the single-pole double-throw switch (SPDT) are the second input terminal of the switch unit, the hilted broadsword
The control terminal of commutator is the control terminal of the switch unit.
12. a kind of characteristic calibration method of voltage controlled oscillator, the voltage controlled oscillator is applied in phase-locked loop circuit, institute
Stating phase-locked loop circuit includes phase frequency detector, charge pump, loop filter, frequency divider and the voltage controlled oscillator, feature
It is, the voltage controlled oscillator, including at least two for given idealized characteristic has the voltage-controlled of different characteristics curve
Oscillating unit, the calibration method include：
Disconnect the connection between the loop filter and the voltage controlled oscillator；
Apply reference voltage to the voltage controlled oscillator, the reference voltage is controlled with the voltage controlled oscillator unit in voltage
Center value is related；
Select the voltage controlled oscillator unit work in described at least two voltage controlled oscillator units with different characteristics curve；
Judge the fractional frequency signal that the frequency of the input signal of the phase-locked loop circuit is generated with the frequency divider frequency whether phase
Deng；
If the frequency of the input signal is equal with the frequency of the fractional frequency signal, the voltage controlled oscillation of selection work at present is kept
Cell operation, and stop applying the reference voltage, connect the loop filter and the voltage controlled oscillator；
If the frequency of the input signal and the frequency of the fractional frequency signal differ, the voltage controlled oscillation list that non-present is selected to work
Member work；
It is calibrated by above-mentioned flow, until the free oscillation frequency of voltage controlled oscillator is equal to the voltage controlled oscillation list of work at present
Frequency corresponding to the characteristic control voltage center value of member, wherein, voltage is equal to the free oscillation frequency in order to control
The frequency of voltage controlled oscillator output signal when zero, the minimum amount of voltage that of voltage and maximum are electric in order to control for control voltage center value
The half of the sum of pressure value.
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| CN105187056B (en) * | 2015-09-06 | 2019-02-26 | 四川九洲电器集团有限责任公司 | A kind of clock signal generating device and clock signal creating method |
| EP3439180B1 (en) * | 2017-08-02 | 2023-03-15 | ams AG | Phase-locked loop circuit |
| US10560109B2 (en) * | 2017-12-29 | 2020-02-11 | Texas Instruments Incorporated | Phased locked loop integrated circuit |
| CN109245761B (en) * | 2018-09-21 | 2021-07-02 | 电子科技大学 | Method for suspending and recovering phase-locked loop |
| CN113541684B (en) * | 2021-06-30 | 2022-08-26 | 睦星科技(北京)有限公司 | Phase-locked loop circuit and calibration method and device thereof |
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| CN1714509A (en) * | 2002-11-22 | 2005-12-28 | 日本电气株式会社 | PLL circuit |
| CN1893278A (en) * | 2005-07-06 | 2007-01-10 | 络达科技股份有限公司 | Phase-lock ring and phase-locking operation method |
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| CN102130684A (en) * | 2011-04-28 | 2011-07-20 | 上海宏力半导体制造有限公司 | Protection circuit of voltage-controlled oscillator (VCO) |
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| US7629856B2 (en) * | 2006-10-27 | 2009-12-08 | Infineon Technologies Ag | Delay stage, ring oscillator, PLL-circuit and method |
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| CN1714509A (en) * | 2002-11-22 | 2005-12-28 | 日本电气株式会社 | PLL circuit |
| CN1893278A (en) * | 2005-07-06 | 2007-01-10 | 络达科技股份有限公司 | Phase-lock ring and phase-locking operation method |
| CN101090263A (en) * | 2006-08-09 | 2007-12-19 | 晨星半导体股份有限公司 | Frequency switching method |
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