CN107979371B - Phase-locked loop and voltage-controlled oscillator thereof - Google Patents
Phase-locked loop and voltage-controlled oscillator thereof Download PDFInfo
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L7/00—Automatic control of frequency or phase; Synchronisation
- H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
- H03L7/08—Details of the phase-locked loop
- H03L7/099—Details of the phase-locked loop concerning mainly the controlled oscillator of the loop
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L7/00—Automatic control of frequency or phase; Synchronisation
- H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
- H03L7/08—Details of the phase-locked loop
- H03L7/14—Details of the phase-locked loop for assuring constant frequency when supply or correction voltages fail or are interrupted
- H03L7/143—Details of the phase-locked loop for assuring constant frequency when supply or correction voltages fail or are interrupted by switching the reference signal of the phase-locked loop
- H03L7/145—Details of the phase-locked loop for assuring constant frequency when supply or correction voltages fail or are interrupted by switching the reference signal of the phase-locked loop the switched reference signal being derived from the controlled oscillator output signal
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Abstract
The invention belongs to the technical field of communication, and provides a phase-locked loop and a voltage-controlled oscillator thereof. In the invention, the voltage-controlled oscillator comprising the voltage-current conversion module, the voltage adjustment module, the mirror image module, the power supply module and the ring oscillator is adopted, so that the voltage-current conversion module outputs a first current and a second current according to the control voltage, the mirror image module generates a power supply voltage according to the first current and the power supply voltage, the difference value between the power supply voltage and the power supply voltage is smaller than a preset threshold value, the voltage adjustment module carries out voltage stabilization and noise reduction treatment on the power supply voltage according to the reference voltage, the power supply module receives the second current, generates a third current according to the second current and provides a working voltage for the ring oscillator according to the processed power supply voltage, and the ring oscillator is convenient to control the frequency of a clock signal according to the third current under the action of the working voltage. The voltage-controlled oscillator provided by the invention can work under low power supply voltage and has large bandwidth power supply inhibition capability.
Description
Technical Field
The present invention relates to the field of communications technologies, and in particular, to a phase locked loop and a voltage controlled oscillator thereof.
Background
As an indispensable part of a high-speed communication system, a phase-locked loop mainly provides a suitable clock frequency for the high-speed communication system, and a voltage-controlled oscillator is used as an important module in the phase-locked loop, so that the performance of the voltage-controlled oscillator is often related to the success or failure of the design of the phase-locked loop.
At present, as the clock frequency becomes higher and higher, the noise performance requirement of the system on the phase-locked loop becomes higher, so that the power supply noise of the system is taken as an important influencing factor of the performance of the voltage-controlled oscillator, and how to design the voltage-controlled oscillator with higher power supply inhibition capability in a larger bandwidth, particularly at medium-high frequency is important; in addition, as the feature size of the chip process is reduced, the power supply voltage of the chip is correspondingly reduced, and the ceiling effect (head room) of the circuit design presents a great challenge to each circuit designer. In summary, how to design a voltage-controlled oscillator with a large bandwidth power supply rejection capability at low supply voltages is a challenge in the industry.
Therefore, it is necessary to provide a technical solution to solve the above technical problems.
Disclosure of Invention
The invention aims to provide a phase-locked loop and a voltage-controlled oscillator thereof, which can work at low power supply voltage and have large bandwidth power supply rejection capability.
The invention is realized in that a voltage controlled oscillator comprises:
the voltage-current conversion module is used for receiving the control voltage and outputting a first current and a second current according to the control voltage;
the mirror image module is connected with the voltage-current conversion module and is used for receiving a power supply voltage and generating a power supply voltage according to the first current and the power supply voltage; wherein the difference between the power supply voltage and the power supply voltage is smaller than a preset threshold value;
the voltage adjusting module is connected with the mirror image module and is used for receiving a reference voltage and performing voltage stabilization and noise reduction treatment on the power supply voltage according to the reference voltage;
the power supply module is connected with the mirror image module and the voltage adjustment module and is used for receiving the second current, generating a third current according to the second current and generating working voltage according to the processed power supply voltage;
and the ring oscillator is connected with the power supply module, is used for working under the action of the working voltage and controls the frequency of the output clock signal according to the third current.
Another object of the present invention is to provide a phase locked loop comprising the voltage controlled oscillator described above.
In the invention, the voltage-controlled oscillator comprising the voltage-current conversion module, the voltage adjustment module, the mirror image module, the power supply module and the ring oscillator is adopted, so that the voltage-current conversion module outputs a first current and a second current according to the control voltage, the mirror image module generates a power supply voltage according to the first current and the power supply voltage, the difference value between the power supply voltage and the power supply voltage is smaller than a preset threshold value, the voltage adjustment module carries out voltage stabilization and noise reduction treatment on the power supply voltage according to the reference voltage, the power supply module generates a third current according to the second current, and provides an operating voltage for the ring oscillator according to the processed power supply voltage, so that the ring oscillator controls the frequency of a clock signal according to the third current under the action of the operating voltage.
Drawings
Fig. 1 is a schematic block diagram of a voltage-controlled oscillator according to an embodiment of the present invention;
fig. 2 is a schematic block diagram of a voltage controlled oscillator according to another embodiment of the present invention;
fig. 3 is a schematic circuit diagram of a voltage-controlled oscillator according to an embodiment of the present invention;
fig. 4 is an equivalent circuit schematic diagram of a voltage adjusting module in a voltage-controlled oscillator according to an embodiment of the invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The implementation of the invention is described in detail below with reference to the specific drawings:
fig. 1 shows a block structure of a voltage-controlled oscillator 10 according to an embodiment of the present invention, and for convenience of explanation, only the portions related to the embodiment are shown, and the details are as follows:
as shown in fig. 1, a voltage-controlled oscillator 10 according to an embodiment of the present invention includes: a voltage-to-current conversion module 100, a voltage regulation module 101, a mirror module 102, a power supply module 103, and a ring oscillator 104.
The voltage-current conversion module 1 receives a control voltage Vctrl, the mirror module 102 is connected with the voltage-current conversion module 100, the voltage adjustment module 101 is connected with the mirror module 102, the power module 103 is connected with the mirror module 102 and the voltage adjustment module 101, and the ring oscillator 104 is connected with the power module 103.
Specifically, the input end of the voltage-current conversion module 100 receives the control voltage Vctrl, the first output end of the voltage-current conversion module 100 is connected with the first input end of the mirror module 102, the second output end of the voltage-current conversion module 100 is connected with the first input end of the power module 103, the second input end of the mirror module 102 receives the power supply voltage VDD, the output end of the mirror module 102 is commonly connected with the first input end of the voltage adjustment module 101 and the second input end of the power module 103, the second input end of the voltage adjustment module 101 receives the reference voltage Vref, the output end of the voltage adjustment module 101 is grounded, the output end of the power module 103 is connected with the input end of the ring oscillator 104, and the output end of the ring oscillator 104 outputs the Clock signal Clock.
Further, the voltage-current conversion module 100 outputs the first current I0 and the second current I1 according to the control voltage Vctrl; the mirror module 102 generates a power supply voltage Vrg according to the first current I0 and the power supply voltage VDD, and the difference value between the power supply voltage Vrg and the power supply voltage VDD is smaller than a preset threshold value; the voltage regulation module 101 performs voltage stabilization and noise reduction processing on the power supply voltage Vrg according to the reference voltage Vref; the power module 103 receives the second current I1, generates a third current I4 according to the second current I1, generates a working voltage Vro according to the processed power voltage Vrg, and outputs the working voltage Vro to the ring oscillator 104, and the ring oscillator 104 operates under the action of the working voltage Vro and controls the frequency of the Clock signal Clock according to the third current I4.
In the embodiment of the present invention, the voltage-current conversion module 100 may be implemented by using an existing voltage-current conversion circuit, which is not described herein again; in addition, the preset threshold refers to a value that a difference between the power supply voltage VDD and the power supply voltage Vrg may not be greater than the value during the circuit design process, for example, if the power supply voltage VDD is 1.0V and the power supply voltage Vrg is 0.9V, the preset threshold is 0.1V at maximum.
Because the feature size reduction in the chip manufacturing process in the prior art correspondingly reduces the power supply voltage of the chip, thereby causing the ceiling effect in the circuit design process, the voltage-controlled oscillator 10 provided by the invention enables the difference between the power supply voltage VDD and the power supply voltage Vrg to be smaller than the preset threshold value, thereby ensuring that the power supply voltage Vrg is not too low, further ensuring that the working voltage Vro obtained according to the power supply voltage Vrg can ensure the normal working of the ring oscillator 104, further enabling the voltage-controlled oscillator 10 to work under low voltage, and eliminating the ceiling effect of the circuit.
In addition, the voltage adjusting module 101 performs voltage stabilization and noise reduction processing on the power supply voltage Vrg according to the reference voltage Vref, so that even if the power supply voltage VDD fluctuates greatly, the power supply voltage Vrg can be stabilized at a fixed value, and cannot fluctuate due to the fluctuation of the power supply voltage VDD, and the power supply voltage Vrg has good noise suppression capability, so that the voltage-controlled oscillator 10 provided by the embodiment of the invention has good power suppression capability.
Further, as a preferred embodiment of the present invention, as shown in fig. 3, the mirroring module 102 includes: the first switching element PM0, the low-pass filter 102a, and the second switching element PM1.
The input terminal of the first switching element PM0 is commonly connected to the input terminal of the second switching element PM1, and receives the supply voltage VDD, that is, the input terminal of the first switching element PM0 is commonly connected to the input terminal of the second switching element PM1 to form the second input terminal of the mirror module 102, the output terminal of the first switching element PM0 is connected to the voltage-current adjustment module 100, that is, the output terminal of the first switching element PM0 is the first input terminal of the mirror module 102, and the output terminal of the first switching element PM0 is commonly connected to the control terminal of the first switching element PM0 and the input terminal of the low-pass filter 102a, the output terminal of the low-pass filter 102a is connected to the control terminal of the second switching element PM1, that is, the output terminal of the second switching element PM1 is the output terminal of the mirror module 102.
In the implementation, the first switching element PM0 and the second switching element PM1 are implemented by P-type MOS transistors, and the gate, the source and the drain of the P-type MOS transistors are respectively a control end, an input end and an output end of the first switching element PM0 and the second switching element PM 1; it should be noted that, in other embodiments of the present invention, the first switching element PM0 and the second switching element PM1 may be implemented by other switching devices, such as a P-type transistor.
Further, as a preferred embodiment of the present invention, as shown in fig. 2, the voltage adjustment module 101 includes: a voltage dividing unit 101a, an amplifying unit 101b, and a switching unit 101c.
The input terminal of the voltage dividing unit 101a is commonly connected with the input terminal of the switch unit 101c and is connected with the mirror module 102 and the power module 103, that is, the input terminal of the voltage dividing unit 101a is commonly connected with the input terminal of the switch unit 101c to form a first input terminal of the voltage adjusting module 101; the output end of the voltage dividing unit 101a is connected with the first input end of the amplifying unit 101b, and the second input end of the amplifying unit 101b receives the reference voltage Vref, that is, the second input end of the amplifying unit 101b is the second input end of the voltage adjusting module 101; the output terminal of the amplifying unit 101b is connected to the control terminal of the switching unit 101c, and the output terminal of the switching unit 101c is grounded, that is, the output terminal of the switching unit 101c is the output terminal of the voltage adjusting module 101.
Specifically, the voltage dividing unit 101a divides the power supply voltage Vrg to generate a divided voltage Vfb; the amplifying unit 101b controls the switching unit 101c to perform voltage stabilization and noise reduction processing on the power supply voltage Vrg based on the divided voltage Vfb and the reference voltage Vref.
Further, as a preferred embodiment of the present invention, as shown in fig. 3, the voltage adjustment module 101 further includes a reference voltage generating circuit 101d, and the reference voltage generating circuit 101d is mainly used for generating the reference voltage Vref, and the specific structure and the working principle thereof can refer to the existing reference voltage circuit and will not be described herein.
Further, as a preferred embodiment of the present invention, as shown in fig. 3, the voltage dividing unit 101a includes: the first voltage dividing resistor R0 and the second voltage dividing resistor R1.
The first end of the second voltage dividing resistor R1 is an input end of the voltage dividing unit 101a, the second end of the second voltage dividing resistor R1 and the first end of the first voltage dividing resistor R0 are commonly connected to form an output end of the voltage dividing unit 101a, and the second end of the first voltage dividing resistor R0 is grounded.
Further, as a preferred embodiment of the present invention, as shown in fig. 3, the amplifying unit 101b includes an amplifier AP, a negative phase input terminal of the amplifier AP is a first input terminal of the amplifying unit 101b, a positive phase input terminal of the amplifier AP is a second input terminal of the amplifying unit 101b, and an output terminal of the amplifier AP is an output terminal of the amplifying unit 101 b.
Further, as a preferred embodiment of the present invention, as shown in fig. 3, the switching unit 101c includes a third switching element PM2, the control terminal of the third switching element PM2 is the control terminal of the switching unit 101c, the input terminal of the third switching element PM2 is the input terminal of the switching unit 101c, and the output terminal of the third switching element PM2 is the output terminal of the switching unit 101c.
In the implementation, the third switching element PM2 is implemented by a P-type MOS transistor, and the gate, the source and the drain of the P-type MOS transistor are a control terminal, an input terminal and an output terminal of the third switching element PM2 respectively; it should be noted that, in other embodiments of the present invention, the third switching element PM2 may be implemented by other switching devices, such as a P-type triode.
Further, as a preferred embodiment of the present invention, as shown in fig. 3, the power module 103 includes: the fourth switching element PM3 and the fifth switching element PM4.
The input end of the fourth switching element PM3 and the input end of the fifth switching element PM4 are commonly connected to form a second input end of the power module 103, the output end of the fourth switching element PM3 is a first input end of the power module 103, and the control end of the fourth switching element PM3 is commonly connected to the output end of the fourth switching element PM3 and the control end of the fifth switching element PM4, and the output end of the fifth switching element PM4 is an output end of the power module 103.
In the implementation, the fourth switching element PM3 and the fifth switching element PM4 are implemented by P-type MOS transistors, and the gate, the source and the drain of the P-type MOS transistors are respectively a control end, an input end and an output end of the fourth switching element PM3 and the fifth switching element PM 4; it should be noted that, in other embodiments of the present invention, the fourth switching element PM3 and the fifth switching element PM4 may be implemented by other switching devices, such as a P-type transistor.
The following specifically describes the operation principle of the voltage-controlled oscillator 10 provided by the present invention, taking the circuit shown in fig. 3 as an example, and the details are as follows:
as shown in fig. 3, as one voltage input of the voltage-controlled oscillator 10, after the control voltage Vctrl is input to the voltage-current conversion module 100, the voltage-current conversion module 100 outputs two paths of currents according to the control voltage Vctrl, one path of current is a first current I0, the other path of current is a second current I1, and the first current I0 and the second current I1 may be represented by equations (1), (2), specifically:
I 0 ＝K V_I0 *Vctrl (1)；
I 1 ＝K V_I1 *Vctrl (2)；
wherein I is 0 For the current value of the first current I0, vctrl is the voltage value of the control voltage Vctrl, K V_I0 The conversion coefficient of the voltage-current conversion module 100 when converting the control voltage Vctrl into the first current I0 may be set as required; i 1 A current value of the second current I1, K V_I1 For the voltage-to-current conversion module 100 to convert the control voltage Vctrl to the second voltageThe conversion factor at current I1, which can be set as desired.
When the voltage-current conversion module 100 outputs the first current I0, the first switch element PM0 generates a voltage Vg0 at the gate thereof under the action of the first current I0, and the relationship between the voltage Vg0 and the first current I0 can be expressed by using the formula (3); wherein Gm0 is the transconductance, V, of the first switching element PM0 g0 Is the voltage value of the voltage Vg 0.
The voltage Vg0 is taken as an input of the low-pass filter 102a, the voltage Vg1 is output after passing through the low-pass filter 102a, the voltage Vg1 is obtained by removing an alternating component and a spike clutter signal compared with the voltage Vg0, and the relationship between the voltage Vg1 and the voltage Vg0 can be represented by the formula (4); where Vg1 is the voltage value of the voltage Vg1, and Hlpf is the gain value of the low-pass filter 102 a.
Vg1＝Vg0*Hlpf (4)；
The voltage Vg1 is used as the control voltage of the second switching element PM1, i.e., the gate voltage of the second switching element PM2, so that the second switching element PM1 outputs a fourth current I2 under the action of the voltage Vg1, the fourth current I2 being a current generated in the channel of the second switching element PM1, and the relationship between the fourth current I2 and the voltage Vg1 can be expressed by the formula (5); wherein I is 2 The fourth current I2 has a current value Gm1 that is the transconductance of the second switching element PM1.
I 2 ＝Vg1*Gm1 (5)；
The relationship between the fourth current I2 and the control voltage Vctrl can be obtained by combining the formula (1), the formula (2), the formula (3), the formula (4) and the formula (5), and can be represented by the formula (6).
As can be seen from equation (6), the fourth current I2 output from the second switching element PM1 is proportional to the control voltage Vctrl.
After the voltage-current conversion module 100 outputs the second current I1, the current flowing through the fourth switching element PM3 is the second current I1, and the fifth switching element PM4 generates the third current I4 according to the second current I1 flowing through the fourth switching element PM3, where the third current I4 is the channel current of the fifth switching element PM4, and the relationship between the third current I4 and the second current I1 can be expressed by using formula (7); wherein I is 4 A current value of the third current I4, I 1 Gm4 is the transconductance of the fifth switching element PM4, and Gm3 is the transconductance of the fourth switching element PM3, which is the current value of the second current I1.
As can be seen from the combination of the formula (2) and the formula (7), the expression of the third current I4 can be expressed by the formula (8).
As can be seen from a combination of fig. 3 and equations (6) and (8), a suitable arrangement isValue of (2) andthe fourth current I2 may be made larger than the sum of the current I5, the second current I1 and the third current I4, and the fourth current I2 and the current I5, the current I3, the second current I1 and the third current I4 reach a balance under the feedback loop formed by the first voltage dividing resistor R0, the second voltage dividing resistor R1, the amplifier AP and the third switching element PM2, so that the voltage controlled oscillator 10 can work normally.
In addition, the third current I4 is used as the input of the ring oscillator 104, and when the ring oscillator 104 operates under the action of the operating voltage Vro, the ring oscillator 104 can output the clock signal Clo according to the third current I4The frequency of ck is adjusted, so that the frequency output by the ring oscillator 104 can meet the requirement of the voltage-controlled oscillator 10, and further meet the requirement of a phase-locked loop, and the specific adjusting process can refer to a formula (9); wherein f clock For the frequency of Clock signal Clock, K ICO Is the frequency current gain.
f clock ＝K ICO *I4 (9)；
Referring to fig. 3 again, it can be seen from fig. 3 that, after the second switching element PM1 outputs the fourth current I2 under the action of the voltage Vg1, the drain of the second switching element PM1 outputs the power voltage Vrg under the action of the fourth current I2 and the power voltage VDD.
In order to ensure that the second switching element PM1 operates normally, the source-drain electrode of the second switching element PM1 needs a voltage vds_pm1 that is greater than the saturation voltage vdsat_pm1 of the second switching element PM1, thereby ensuring that the drain electrode of the second switching element PM1 has a higher output impedance. Since the saturation voltage vdsat_pm1 is a small value, for example, 100mV, the source-drain voltage drop of the second switching element PM1 has a relatively small advantage, that is, the difference between the power supply voltage Vrg and the power supply voltage VDD is small, so that a large load is not imposed on the ceiling effect (head room) of the power supply voltage VDD, and the voltage-controlled oscillator 10 can be effectively ensured to operate when the power supply voltage VDD is relatively low.
Further, the reference voltage generating circuit 101d outputs the reference voltage Vref. The reference voltage Vref is a negative phase input of the amplifier AP, and a positive phase input of the amplifier AP is a divided voltage Vfb obtained by dividing the power supply voltage Vrg by the first dividing resistor R0 and the second dividing resistor R1. Since the amplifier AP operates when the reference voltage Vref is equal to the divided voltage Vfb, the amplifier AP may output a control signal to control the third switching element PM2 when the reference voltage Vref is equal to the divided voltage Vfb, thereby causing the third switching element PM2 to stabilize the power supply voltage Vrg.
In addition, since the divided voltage Vfb is obtained by dividing the power supply voltage Vrg by the first and second dividing resistors R0 and R1, when the reference voltage Vref is equal to the divided voltage Vfb, the power supply voltage Vrg can be obtained by using the formula (10)A row representation; wherein V is rg_DC V is the voltage value of the power supply voltage Vrg ref As a voltage value of the reference voltage Vref, R1 is a resistance value of the second voltage dividing resistor R1, and R0 is a resistance value of the first voltage dividing resistor R0.
As can be seen from equation (10) and fig. 3, the power supply voltage Vrg forms a low-resistance node under the feedback loop formed by the second voltage dividing resistor R1, the first voltage dividing resistor R0, the amplifier AP and the third switching element PM2, and the voltage Vrg of the node can be kept stable under the feedback loop.
Further, since the power supply voltage VDD contains a noise signal, in order to make the noise signal have no influence on the voltage-controlled oscillator 10, a node of the operating voltage Vro of the ring oscillator 104 needs to have a strong power supply rejection capability, and since the operating voltage Vro of the ring oscillator 104 is obtained from the power supply voltage Vrg, the power supply rejection capability of the node of the operating voltage Vro can be deduced and explained from the power supply rejection capability of the node of the power supply voltage Vrg.
Specifically, as shown in fig. 3, at the voltage node of the power supply voltage Vrg, the impedance looking into the power supply direction is denoted as Ri1, and the impedance looking into the ground direction is denoted as Ri2; at the voltage node of the operating voltage Vro, the impedance looking into the power supply direction is denoted as Ri3, and the impedance looking into the ground direction is denoted as Ri4. As can be seen from the circuit shown in fig. 3, the power supply rejection ratio of the voltage node of the power supply voltage vrg is:
wherein PSRR Vrg As the power supply rejection ratio of the voltage node of the power supply voltage Vrg, ri1 is the value of the impedance Ri1, ri2 is the value of the impedance Ri2, and since Ri1 is generally much larger than Ri2, the power supply rejection ratio of the voltage node of the power supply voltage Vrg can also be expressed by the formula (12).
Further, as can be seen from the circuit shown in fig. 3, the power supply rejection ratio of the voltage node of the operating voltage Vro is:
where Ri4 is the value of impedance Ri4, ri3 is the value of impedance Ri3, and the sum of Ri3 and Ri4 is much greater than Ri2, ri3 is much greater than Ri4.
Further, the value Ri1 of the impedance Ri1 is equal to the value Ro1 of the drain saturation resistance of the second switching element PM1, the value Ri3 of the impedance Ri3 is equal to the value Ro4 of the drain saturation resistance of the fifth switching element PM4, the value Ri4 of the impedance Ri4 is equal to the value Rosc of the equivalent input impedance of the ring oscillator 104, and the value Ri2 of the impedance Ri2 can refer to the following calculation procedure.
Specifically, as shown in fig. 4, the voltage node of the power supply voltage Vrg corresponds to a voltage source, and the voltage of the voltage source changes to Δv and the current changes to ΔiWherein DeltaV is the voltage variation and DeltaI is the current variation, due to +.>Wherein Gop is the value of gain Gop of the amplifier AP, then +.>Substituting the expressions of Ri1, ri2, ri3, and Ri4 into equation (13) can result in equation (14):
due to the gain of the amplifier AP being preserved within the bandwidthMaintaining a constant gain which decreases when the frequency is higher than the bandwidth, so that the value Gop of the gain Gop of the amplifier AP is greater when the frequency is lowerFar greater than 1, then:
when the value Gop of the gain Gop of the amplifier AP gradually decreases until Gop is 0, then:
since gm2 Ro1 Ro4 is a relatively large value and Rosc is a relatively small value, it can be seen from equation (15) and equation (16) that the voltage node of the operating voltage Vro can still maintain a relatively small power supply rejection ratio, and since the power supply rejection ratio refers to the noise gain caused by the early noise of the power supply voltage at a certain voltage node, the smaller the value is, which indicates that the better the power supply rejection capability of the voltage node, that is, the voltage-controlled oscillator 10 provided by the present invention has a good power supply rejection capability regardless of the frequency.
Further, the present invention also provides a phase locked loop comprising the voltage controlled oscillator 10. It should be noted that, since the voltage-controlled oscillator 10 of the pll provided in the embodiment of the present invention is the same as the voltage-controlled oscillator 10 of fig. 1 to 4, the specific working principle of the voltage-controlled oscillator 10 of the pll provided in the embodiment of the present invention may refer to the foregoing detailed description about fig. 1 to 4, and will not be repeated here.
In the invention, the voltage-controlled oscillator comprising the voltage-current conversion module, the voltage adjustment module, the mirror image module, the power supply module and the ring oscillator is adopted, so that the voltage-current conversion module outputs a first current and a second current according to the control voltage, the mirror image module generates a power supply voltage according to the first current and the power supply voltage, the difference value between the power supply voltage and the power supply voltage is smaller than a preset threshold value, the voltage adjustment module carries out voltage stabilization and noise reduction treatment on the power supply voltage according to the reference voltage, the power supply module generates a third current according to the second current and provides an operating voltage for the ring oscillator according to the processed power supply voltage, the ring oscillator is used for controlling the frequency of a clock signal according to the third current under the action of the operating voltage, and the operating voltage of the ring oscillator is stable when the power supply voltage fluctuates greatly, and the power supply voltage can also ensure the ring oscillator to operate under the low power supply voltage when the power supply voltage is smaller.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (9)
1. A voltage controlled oscillator, the voltage controlled oscillator comprising:
the voltage-current conversion module is used for receiving the control voltage and outputting a first current and a second current according to the control voltage, wherein the first current flows to the mirror image module, and the second current flows to the power supply module;
the mirror image module is connected with the voltage-current conversion module and is used for receiving a power supply voltage and generating a power supply voltage according to the first current and the power supply voltage; wherein the difference between the power supply voltage and the power supply voltage is smaller than a preset threshold value;
the voltage adjusting module is connected with the mirror image module and is used for receiving a reference voltage and performing voltage stabilization and noise reduction treatment on the power supply voltage according to the reference voltage;
the power supply module is connected with the mirror image module and the voltage adjustment module and is used for receiving the second current, generating a third current according to the second current and generating a working voltage according to the processed power supply voltage, wherein the third current flows to the ring oscillator;
the ring oscillator is connected with the power supply module, is used for working under the action of the working voltage and controls the frequency of the output clock signal according to the third current;
the voltage regulation module comprises a voltage division unit, an amplifying unit and a switch unit;
the input end of the voltage dividing unit is commonly connected with the input end of the switch unit and is connected with the mirror image module and the power supply module, the output end of the voltage dividing unit is connected with the first input end of the amplifying unit, the second input end of the amplifying unit receives the reference voltage, the output end of the amplifying unit is connected with the control end of the switch unit, and the output end of the switch unit is grounded;
the voltage dividing unit divides the power supply voltage to generate a divided voltage;
the amplifying unit controls the switching unit to perform voltage stabilization and noise reduction processing on the power supply voltage according to the divided voltage and the reference voltage.
2. The voltage controlled oscillator of claim 1, wherein the mirroring module comprises:
a first switching element, a low-pass filter, and a second switching element;
the input end of the first switching element is commonly connected with the input end of the second switching element and receives the power supply voltage, the output end of the first switching element is connected with the voltage-current conversion module, the output end of the first switching element is commonly connected with the control end of the first switching element and the input end of the low-pass filter, the output end of the low-pass filter is connected with the control end of the second switching element, and the output end of the second switching element is connected with the voltage regulation module and the power supply module.
3. The voltage controlled oscillator of claim 2, wherein the first switching element and the second switching element are P-type MOS transistors.
4. The voltage controlled oscillator of claim 1, wherein the voltage dividing unit comprises:
the first voltage dividing resistor and the second voltage dividing resistor;
the first end of the first voltage dividing resistor is an input end of the voltage dividing unit, the second end of the first voltage dividing resistor and the second end of the second voltage dividing resistor are connected together to form an output end of the voltage dividing unit, and the second end of the second voltage dividing resistor is grounded.
5. The voltage controlled oscillator of claim 1, wherein the amplifying unit comprises an amplifier, a negative phase input of the amplifier being a first input of the amplifying unit, a positive phase input of the amplifier being a second input of the amplifying unit, and an output of the amplifier being an output of the amplifying unit.
6. The voltage controlled oscillator of claim 1, wherein the switching unit comprises a third switching element, a control terminal of the third switching element being a control terminal of the switching unit, an input terminal of the third switching element being an input terminal of the switching unit, and an output terminal of the third switching element being an output terminal of the switching unit.
7. The voltage controlled oscillator of claim 6, wherein the third switching element is a P-type MOS transistor.
8. The voltage controlled oscillator of claim 1, wherein the power supply module comprises:
a fourth switching element and a fifth switching element;
the input end of the fourth switching element is commonly connected with the input end of the fifth switching element and is connected with the mirror module and the voltage adjustment module, the output end of the fourth switching element receives the second current, the control end of the fourth switching element is commonly connected with the output end of the fourth switching element and the control end of the fifth switching element, and the output end of the fifth switching element is connected with the ring oscillator and outputs the working voltage and the third current.
9. A phase locked loop comprising a voltage controlled oscillator as claimed in any one of claims 1 to 8.
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