A charge pump and phase-locked loop with temperature compensation

Abstract

The present invention discloses a charge pump and phase-locked loop with temperature compensation. The charge pump includes a constant current source, a temperature-controlled current source, a proportional module, and a control module. The proportional module is used to combine the constant current source and the temperature-controlled current source in a certain ratio and output the combined current to a control unit. When the charge pump injects current into the subsequent circuit in the forward direction, the control module injects a current obtained by combining the constant current source and the temperature-controlled current source in a certain ratio into the subsequent circuit. When the charge pump draws current from the subsequent circuit in the reverse direction, the control module draws a current obtained by combining the constant current source and the temperature-controlled current source in a certain ratio from the subsequent circuit. In this solution, compensation is achieved by combining the PTAT current and the constant current in a certain ratio to generate a KVCO power supply voltage, thereby achieving temperature compensation while avoiding overcompensation.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a charge pump and a phase-locked loop with temperature compensation. Background Art

[0002] One of the key specifications of a phase-locked loop circuit is loop bandwidth, which depends on the charge pump current, loop filter resistance, and voltage-controlled oscillator (VCO) gain (Kvco). The VCO gain depends on the process-voltage-temperature (PVT) relationship, with temperature being a significant factor. Changes in the chip's operating temperature cause changes in the loop bandwidth, degrading chip performance.

[0003] In the prior art, either no temperature-related compensation is performed, or pure PTAT current is used for compensation. However, this solution can easily lead to over-compensation problems. Summary of the Invention

[0004] In order to solve this problem, the patent of this invention introduces a temperature compensation method with adjustable ratio at the charge pump to reduce the impact of the phase-locked loop circuit bandwidth on temperature, thereby improving chip performance.

[0005] The present invention provides a charge pump with temperature compensation, comprising:

[0006] It includes a constant current source, a temperature-controlled current source, a proportional module and a control module, wherein the proportional module is used to combine the constant current source and the temperature-controlled current source in a certain proportion and output the combined current to the control unit;

[0007] When the charge pump injects forward current into the subsequent circuit, the control module injects a current obtained by combining a constant current source and a temperature-controlled current source in a certain ratio into the subsequent circuit;

[0008] When the charge pump reversely extracts current from the subsequent stage, the control module extracts a current that is a combination of a constant current source and a temperature-controlled current source in a certain proportion from the subsequent stage circuit.

[0009] The present invention also provides a phase-locked loop with temperature compensation, comprising:

[0010] Voltage controlled oscillator, low-pass filter, charge pump and phase frequency detector;

[0011] The charge pump includes a constant current source, a temperature-controlled current source, a control module, and a proportional module, wherein the proportional module is used to combine the constant current source and the temperature-controlled current source in a certain ratio and output the combined current to the control unit;

[0012] When the charge pump outputs a positive direction to the low-pass filter, the control module inputs a current obtained by combining a constant current source and a temperature-controlled current source in a certain ratio to the low-pass filter;

[0013] When the charge pump reversely flows current from the low-pass filter, the control module extracts a current from the low-pass filter that is a combination of a constant current source and a temperature-controlled current source in a certain ratio.

[0014] Compared with the existing solutions, the present invention has the following advantages:

[0015] In this solution, the PTAT current and the constant current are combined in a certain ratio to generate the control voltage of KVCO to compensate the loop bandwidth, thereby achieving temperature compensation while avoiding the over-compensation problem. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0017] Figure 1 This is a schematic diagram of the structure of a phase-locked loop with temperature compensation according to the present invention;

[0018] Figure 2 A schematic diagram of a charge pump with temperature compensation according to an embodiment of the invention;

[0019] Figure 3 A circuit diagram of a charge pump with temperature compensation according to an embodiment of the invention;

[0020] Figure 4 A circuit diagram of a proportional module of a charge pump with temperature compensation according to an embodiment of the invention;

[0021] Figure 5 A current source circuit diagram of a charge pump with temperature compensation according to an embodiment of the invention. DETAILED DESCRIPTION

[0022] A typical phase-locked loop circuit is as follows: Figure 1 As shown in the figure, it consists of a voltage-controlled oscillator (VCO), a low-pass filter (LPF), a charge pump (CP), a frequency divider (DIV) and a phase-frequency detector (PFD).

[0023] The bandwidth of a phase-locked loop is one of its key specifications. The loop bandwidth affects the stability and system performance of the phase-locked loop. The loop bandwidth is:

[0024] Among them I cp is the current at the charge pump, R lf is the loop filter resistance, Kvco is the gain of the oscillator. All parameters are affected by process angle and temperature, which leads to large process angle and temperature fluctuations in the phase-locked loop bandwidth. In traditional designs, cp Usually a bandgap reference voltage (V bgr ) and the poly resistor (R poly ) generated by the current (i.e., I pp ) The loop filter resistor R lf Usually it is also the poly resistor in the chip, so there will be I cp *R lf =V bgr *R lf / R poly Since the bandgap reference voltage (V bgr ) is little affected by temperature and process, so if R lf / R poly If the match is good, then It is also almost unaffected by temperature and process. vco It is relatively complex and varies with temperature, process, and control voltage. vco Usually, the chip will be calibrated when it is powered on. During this process, the process deviation can be calibrated out, that is, K vco As the process deviation is calibrated out, the temperature may change during normal operation of the chip after calibration, which will cause K vco For the ring oscillator, the temperature increases, K vco As a result, the loop bandwidth also decreases.

[0025] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0026] refer to Figure 1 and Figure 2 The present invention provides a charge pump with temperature compensation, comprising a constant current source, a temperature-controlled current source, a proportional module and a control module, wherein the proportional module is used to combine the constant current source and the temperature-controlled current source in a certain ratio and output the combined current to a control unit; when the charge pump outputs forward current to the subsequent circuit, the control module outputs a current that is a combination of the constant current source and the temperature-controlled current source in a certain ratio; when the charge pump reversely returns current from the subsequent circuit, the control module inputs a current that is a combination of the constant current source and the temperature-controlled current source in a certain ratio from the subsequent circuit.

[0027] In one embodiment, if Figure 3As shown, the control module includes a first current mirror 110 connected to a negative power supply (GND in this embodiment) and a second current mirror 120 connected to a high level. The reference current input terminal of the first current mirror 110 is connected to a current output terminal that is a combination of a constant current source and a temperature-controlled current source in a certain ratio. In this embodiment, the output terminal of the proportional module is connected. The first current output terminal of the first current mirror 110 is connected to the reference current input terminal of the second current mirror 120. The second current output terminal of the first current mirror 110 is connected to the current output terminal of the second current mirror 120 through the control module.

[0028] Continue to refer Figure 3 In one embodiment, the control module further includes a first forward switch S1 and a first reverse switch S2 connected in series between the current output end of the second current mirror 120 and the second current output end of the first current mirror 110, and the connection point of the first forward switch S1 and the first reverse switch S2 is connected to the next-stage low-pass filter LPD.

[0029] Continue to refer Figure 3 In one embodiment, the control module further includes a second forward switch S3, a second reverse switch S4, and an operational amplifier 130, wherein the second forward switch S3 and the second reverse switch S4 are connected in series between the second current output terminal of the first current mirror 110 and the current output terminal of the second current mirror 120, the positive input terminal of the operational amplifier 130 is connected to the connection point of the first forward switch S1 and the first reverse switch S2, and the negative input terminal and the output terminal of the operational amplifier are connected to the connection point of the second forward switch S3 and the second reverse switch S4.

[0030] Specifically in one embodiment, the first current mirror 110 includes a first MMOS transistor N1, a second NMOS transistor N2, and a third NMOS transistor N3. The sources of the first MMOS transistor N1, the second NMOS transistor N2, and the third NMOS transistor N3 are grounded, and the gates are connected to the drain of the first NMOS transistor N1. The drain of the first NMOS transistor N1 serves as a reference current input terminal of the first current mirror, the drain of the second NMOS transistor N2 serves as a first current output terminal, and the drain of the third NMOS transistor N3 serves as another first current output terminal.

[0031] The second current mirror 120 includes a first PMOS transistor P1 and a second PMOS transistor P2. The sources of the first PMOS transistor P1 and the second PMOS transistor P2 are connected to the positive power supply voltage, and the gates are connected to the drain of the first PMOS transistor P1. The drain of the first PMOS transistor P1 serves as the reference current input terminal of the second current mirror, and the drain of the second PMOS transistor P2 serves as the second current output terminal.

[0032] In one embodiment, reference Figure 4The temperature-controlled current source is a PTAT current source, and the proportional module includes: a third current mirror 210, which is used to provide a mirror current of the PTAT current source; a first current mirror group 220 connected in parallel, which is used to provide a proportional current of the PTAT current; a fourth current mirror 230, which is used to provide a mirror current of the constant current source; a second current mirror group 240 connected in parallel, which is used to provide a proportional current of the constant current; the outputs of the first current mirror group and the second current mirror group are connected to output a current obtained by combining the constant current source and the temperature-controlled current source in a certain proportion.

[0033] In this embodiment, the proportional module further includes a gating circuit, which achieves dynamic regulation of the combined current by selecting the number of current mirrors in the first current mirror group and the second current mirror group.

[0034] In this embodiment, the gating circuit further includes: a three-bit binary code, where one code corresponds to a proportional selection relationship between a constant current source and a temperature-controlled current source.

[0035] Specifically, the first current mirror group 220 includes PMOS transistors P9, P10, P11, and P12. The gate and drain of the PMOS transistor P9 are connected to the current output terminal of the third current mirror 210, and the source is connected to the power line. The gates of the PMOS transistors P10, P11, and P12 are connected to the gate of the PMOS transistor P9, and the drains are connected to the output terminal to output a certain proportion of the temperature-controlled current. The sources of the PMOS transistors P10, P11, and P12 are respectively connected to the power line through their gating circuits. Figure 4 The PMOS transistor P10 is gated by the PMOS transistor P15, whose gate is the gate control terminal and is controlled by the digitally encoded Ictrl[2] bit. The PMOS transistors P11 and P12 are controlled by the digitally encoded Ictrl[1] and Ictrl[0] bits respectively.

[0036] The second current mirror group 240 includes PMOS transistors P20, P21, P23, P24, and P25. The gate and drain of the PMOS transistor P20 are connected to the current output terminal of the fourth current mirror 230, and the source is connected to the power line. The gates of the PMOS transistors P21, P23, P24, and P25 are connected to the gate of the PMOS transistor P20, and the drains are connected to the output terminal, which is connected to the output of the first current mirror group. The second current mirror outputs a constant current of a certain proportion. The sources of the PMOS transistors P21, P23, and P24 are respectively connected to the power line through their gating circuits. Figure 4The PMOS transistor P21 is gated using a PMOS transistor P26, whose gate serves as a gate control terminal and is controlled by the digitally encoded Ictrl[2] bit. PMOS transistors P27 and P28 are controlled, respectively, by the digitally encoded Ictrl[1] and Ictrl[0] bits. The source of the PMOS transistor P25 is connected to the power line via a PMOS transistor P29, whose gate is connected to the negative power supply.

[0037] In other embodiments, the current mirror group may include a different number of current mirrors to achieve an output current more suitable for the application.

[0038] The constant current source in the present invention is primarily a current source generated by a bandgap reference voltage and a poly resistor within the chip. The temperature-controlled current source utilizes a PTAT (Proportional To Absolute Temperature) current source, which generates a PTAT current that is proportional to the absolute temperature. The PTAT current is generated through a specific circuit structure, typically including the temperature-dependent characteristics of a diode or transistor. The magnitude of the PTAT current increases linearly with increasing temperature. This is because the voltage drop (such as the base-emitter voltage) of a diode or transistor decreases with increasing temperature, resulting in an increase in current. The system comprises two transistors of different sizes, and by controlling the ratio of their current densities, a current proportional to temperature is generated.

[0039] In one embodiment, the temperature controlled current source and the constant current source, such as Figure 5 As shown in the figure, this embodiment includes a PTAT current source and a Poly current source circuit. These circuits are used to generate a temperature-compensated reference current within the chip. The output current of the PTAT current source is proportional to the absolute temperature. This current source generates the PTAT current by utilizing the base-emitter voltage difference between BJTs (bipolar junction transistors). Bipolar transistors T1 and T2 operate at different current densities, generating different base-emitter voltages (V) due to their different emitter currents. BE Resistors R1 and R2, connected to the emitters of T1 and T2, respectively, determine the current ratio. Resistor R3 stabilizes the current. Operational amplifier A1 maintains the base-emitter voltage difference between bipolar transistors T1 and T2 to ensure the generation of current Iptat. This circuit utilizes the temperature characteristic of (VBE_T1 - VBE_T2) to generate a current Iptat that is proportional to temperature.

[0040] The poly current source circuit generates a poly current, which is typically process-dependent. Because it uses the bandgap voltage as the input to amplifier A2, this current source maintains a relatively stable output despite temperature fluctuations. PMOS transistors P31 and P32 control the PTAT current, Iptat. Operational amplifier A2, P33, and R4 form an analog loop to generate the Ipp current, which is mirrored by P34.

[0041] Thus, a PTAT current source generates a current proportional to temperature and is usually used for temperature sensing or temperature compensation. A Poly current source generates a current that is independent of temperature and is usually used for bias generation or reference generation for other circuits.

[0042] The present invention also provides a temperature-compensated phase-locked loop (PLL), comprising: a voltage-controlled oscillator (VCO) with a power supply voltage (VDDVCO) for generating a frequency-adjustable clock signal for a phase-locked loop (PLL); a low-pass filter (LPF) for providing a filtered analog voltage control signal to the VCO; and a charge pump (CP) for inputting or extracting current into or from the LPF, thereby indirectly generating the control voltage signal required by the VCO.

[0043] The PFD is used to provide a control signal to the charge pump (CP), so that the charge pump outputs a control voltage to adjust the frequency and phase of the voltage-controlled oscillator (VCO).

[0044] The current pulses output by the charge pump pass through a low-pass filter (LPF) to remove high-frequency components, resulting in a smooth voltage signal. This voltage signal serves as the control voltage for the VCO. The VCO's output frequency is controlled by the input control voltage. As the control voltage changes, the VCO's output frequency increases or decreases accordingly.

[0045] When the PFD detects that the reference and feedback signals are out of sync, the charge pump adjusts the control voltage, gradually locking the VCO output frequency to the same frequency as the reference signal. When the reference and feedback signals are in sync in frequency and phase, the UP and DOWN signals alternate, causing the control voltage to reach a balanced value, and the VCO output frequency stabilizes at the target frequency.

[0046] The charge pump (CP) may refer to the above embodiment and will not be described in detail.

[0047] The loop bandwidth calculation formula is as follows:

[0048]

[0049] The charge pump (CP) is designed to close the first and second forward switches S1 and S2 when the UP signal is active. The second current mirror injects current into the output node Q through the first forward switch S1, increasing the control voltage. The injected current at the output node Q is Icp = m*Ipp(1+(1-m) / m*(1+0.05625*T)). As the temperature rises, the VCO gain Kvco decreases, causing the loop bandwidth fc to decrease. The present invention adds a PTAT current source at Icp. Its current IPTAT increases with increasing temperature, while the output current Ipp of the constant current source remains constant. This increases the output node current Icp (the combination of IPTAT and Ipp), increasing the current I flowing into or out of the CP. This compensates for the temperature-dependent effect of Kvco on the loop bandwidth, ultimately minimizing loop bandwidth variations.

[0050] From the above formula, we can see that: for the ring oscillator: T increases, Kvco decreases, decline;

[0051] Then after Icp is compensated by Iptat: T increases, Icp increases, rise;

[0052] The present invention, after compensation

[0053] Temperature changes can cause the VCO gain K vco Changes in the charge pump current can also cause changes in the loop bandwidth. Therefore, the present invention uses temperature to compensate the charge pump current to a certain extent, thereby offsetting the overall loop bandwidth changes caused by VCO temperature changes as much as possible.

[0054] The charge pump of the present invention combines a PTAT current with a constant current to create a temperature-dependent charge pump. The PTAT current is a current that is proportional to temperature. As the temperature rises, the current increases. A constant current is a current that does not vary with temperature and remains constant. By combining the PTAT current and the constant current, a temperature-dependent charge pump can be designed so that the output current exhibits desired temperature characteristics. In this embodiment, a PTAT current source generates the PTAT current, while a constant current source generates the constant current.

[0055] In one embodiment, specifically, In the bandgap reference circuit, k, q, m, and n are constants, and T is the temperature in Fahrenheit. ptat It is also a poly resistor in the chip. In actual implementation, select a certain temperature (such as ), deliberately let I PTATCurrent and I PP The current is the same, that is Then we can get

[0056] ,Right now

[0057]

[0058] Therefore, in Figure 3 There are ,

[0059] Right now:

[0060] Among them, 0 <m<=1;

[0061] If m=1, then the current I CP The temperature compensation coefficient is 0. If m changes from 1 to 0, then I CP Middle I PTAT The proportion will gradually increase. Figure 3 Use Ictrl <2:0> to adjust I PTAT and I PP The corresponding K is listed in the following table vco Compensation range.

[0062]

[0063] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A charge pump with temperature compensation, characterized in that: include: It includes a constant current source, a temperature-controlled current source, a proportional module and a control module, wherein the proportional module is used to combine the constant current source and the temperature-controlled current source in a certain proportion and output the combined current to the control unit; When the charge pump injects forward current into the subsequent circuit, the control module injects a current obtained by combining a constant current source and a temperature-controlled current source in a certain ratio into the subsequent circuit; When the charge pump extracts current from the next stage in reverse, the control module extracts a current from the next stage circuit that is a combination of a constant current source and a temperature-controlled current source in a certain ratio; The control module includes a first current mirror connected to a negative power supply and a second current mirror connected to a positive power supply, a reference current input terminal of the first current mirror connected to a current output terminal of a combination of a constant current source and a temperature-controlled current source in a certain ratio, the first current output terminal connected to the reference current input terminal of the second current mirror, and the second current output terminal connected to the current output terminal of the second current mirror through the control module; the control module also includes a first forward switch and a first reverse switch connected in series between the current output terminal of the second current mirror and the second current output terminal of the first current mirror, and the connection point of the first forward switch and the first reverse switch is connected to a subsequent low-pass filter; the control module also includes a second forward switch, a second reverse switch and an operational amplifier, wherein the second forward switch and the second reverse switch are connected in series between the second current output terminal of the first current mirror and the current output terminal of the second current mirror, the positive input terminal of the operational amplifier is connected to the connection point of the first forward switch and the first reverse switch, and the negative input terminal and the output terminal of the operational amplifier are connected to the connection point of the second forward switch and the second reverse switch; The proportional module includes: a third current mirror, configured to provide a mirror current of the PTAT current source; A first current mirror group connected in parallel, for providing a proportional current of the PTAT current; a fourth current mirror, configured to provide a mirror current of the constant current source; a second current mirror group connected in parallel, for providing a proportional current of the constant current; The outputs of the first current mirror group and the second current mirror group are connected to output a current obtained by combining the constant current source and the temperature-controlled current source in a certain ratio; The proportional module further includes a gating circuit for dynamically adjusting the combined current by selecting the number of current mirrors in the first current mirror group and the second current mirror group.

2. The charge pump with temperature compensation according to claim 1, wherein: The temperature-controlled current source is a PTAT current source.

3. The charge pump with temperature compensation according to claim 2, wherein: The output current of the PTAT current source is I PTAT =(kT / q)*In(mn) / R ptat , where k, q, m, and n are constants, T is the temperature in Fahrenheit, and R ptat It is a poly resistor inside the chip.

4. The charge pump with temperature compensation according to claim 3, wherein: At 0°C, the output current of the PTAT current source I PTAT and the output current I of the constant current source PP , I cp =m*I pp +(1-m)*I ptat .

5. The charge pump with temperature compensation according to claim 4, wherein: Also includes: The gating circuit is coded in three-bit binary format, with one code corresponding to a proportional selection relationship between a constant current source and a temperature-controlled current source.

6. A phase-locked loop comprising a charge pump with temperature compensation according to any one of claims 1 to 5, characterized in that: include: Voltage controlled oscillator, low-pass filter, charge pump and phase frequency detector; The charge pump includes a constant current source, a temperature-controlled current source, a control module, and a proportional module, wherein the proportional module is used to combine the constant current source and the temperature-controlled current source in a certain ratio and output the combined current to the control unit; When the charge pump outputs a positive direction to the low-pass filter, the control module inputs a current obtained by combining a constant current source and a temperature-controlled current source in a certain ratio to the low-pass filter; When the charge pump reversely flows current from the low-pass filter, the control module extracts a current from the low-pass filter that is a combination of a constant current source and a temperature-controlled current source in a certain ratio.

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