CN109756204B - Filter, oscillation generating circuit and electronic device - Google Patents
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Abstract
The invention discloses a filter, an oscillation generating circuit and an electronic device. The filter comprises a filter circuit, wherein the filter circuit comprises a plurality of MOS (metal oxide semiconductor) tubes, a voltage input end, a control end and a voltage output end, the grid electrodes of the MOS tubes are electrically connected with the control end, the voltage input end is used as the input end of the filter, and the voltage output end is used as the output end of the filter; the voltage source with temperature compensation and the threshold compensation circuit, the input end of the threshold compensation circuit is electrically connected with the output end of the voltage source with temperature compensation, and the output end of the threshold compensation circuit is electrically connected with the control end of the filter circuit. Compared with the prior art, the embodiment of the invention improves the filtering effect of the filter, reduces the phase noise of the oscillation generating circuit, and improves the stability of the phase noise performance of the oscillation generating circuit under different environments.
Description
Technical Field
Embodiments of the present invention relate to the field of semiconductor technologies, and in particular, to a filter, an oscillation generating circuit, and an electronic device.
Background
The oscillation generating circuit (oscillator) of the common consumer electronic product has no strict requirement on the phase noise index, and only a relatively stable input clock signal can be provided for a control chip and other circuits to meet the requirement. But in high-end applications (such as communication, base station synchronization, etc.), phase noise is a required indicator, and directly affects the quality of service (Quality of Services, qoS) of the communication.
The phase noise of the oscillation generating circuit is affected in many ways, including noise of the oscillation generating circuit's own components, interference of a power supply or a circuit power supply system, and interference of peripheral circuits. In the prior art, a complementary Metal-Oxide-semiconductor (CMOS) filter circuit employs a Metal-Oxide-semiconductor field effect transistor (MOSFET) as a filter device. However, the noise of the MOSFET device generally has thermal noise (thermal noise) and flicker noise (flicker noise), and the corner frequency (corner frequency) of the flicker noise of the CMOS is higher than that of the Bipolar transistor (Bipolar device), so that the existing filter has the problems of large interference and poor filtering effect.
Disclosure of Invention
The invention provides a filter, an oscillation generating circuit and an electronic device, which are used for reducing interference in the filter and improving the filtering effect of the filter.
In a first aspect, an embodiment of the present invention provides a filter, including:
the filter circuit comprises a plurality of MOS tubes, a voltage input end, a control end and a voltage output end, wherein the grid electrodes of the MOS tubes are electrically connected with the control end, the voltage input end is used as the input end of the filter, and the voltage output end is used as the output end of the filter;
the voltage source with temperature compensation and the threshold compensation circuit, the input end of the threshold compensation circuit is electrically connected with the output end of the voltage source with temperature compensation, and the output end of the threshold compensation circuit is electrically connected with the control end of the filter circuit.
Optionally, the threshold compensation circuit includes:
the first end of the current source is electrically connected with the first power supply;
the first input end and the control end of the first current mirror are electrically connected with the second end of the current source, the second input end of the first current mirror is electrically connected with the control end of the filter circuit, and the first output end and the second output end of the first current mirror are electrically connected with the second power supply;
and the first end of the first transistor is electrically connected with the input end of the threshold compensation circuit, and the control end and the second end of the first transistor are electrically connected with the control end of the filter circuit.
Optionally, the first transistor is a MOS transistor.
Optionally, the voltage source with temperature compensation includes:
the first input end, the second input end and the third input end of the second current mirror are electrically connected with a first power supply, and the first output end of the second current mirror is electrically connected with the output end of the voltage source with temperature compensation;
the first input end and the control end of the third current mirror are electrically connected with the second output end of the second current mirror, and the third output end and the control end of the second current mirror are electrically connected with the second input end of the third current mirror;
a first resistor, wherein a first end of the first resistor is electrically connected with a second output end of the third current mirror;
a second transistor, wherein a first end of the second transistor is electrically connected with a second end of the first resistor, and a second end and a control end of the second transistor are electrically connected with a second power supply;
a third transistor, a first end of which is electrically connected with a first output end of the third current mirror, and a second end and a control end of which are electrically connected with the second power supply;
and the first end of the second resistor is electrically connected with the output end of the voltage source with temperature compensation, and the second end of the second resistor is electrically connected with the second power supply.
Optionally, the second transistor and the third transistor are dual-stage junction transistors.
Optionally, the filtering circuit includes:
at least two fourth transistors connected in series between a voltage input terminal and a voltage output terminal of the filter circuit;
and the control end of the fifth transistor is electrically connected with the voltage output end of the filter circuit, and the first end and the second end are electrically connected with a second power supply.
Optionally, the filtering circuit further includes:
and a sixth transistor connected in series between the voltage input terminal and the voltage output terminal of the filter circuit, the control terminal of the sixth transistor inputting an enable signal.
In a second aspect, an embodiment of the present invention also provides an oscillation generating circuit including:
a reference source;
a filter according to any embodiment of the present invention, an input of the filter is electrically connected to an output of the reference source;
the input end of the reference voltage generator is electrically connected with the output end of the filter;
the first input end of the first voltage stabilizer is electrically connected with the first output end of the reference voltage generator, and the second input end of the reference voltage generator is electrically connected with the second output end of the reference voltage generator;
the input end of the second voltage stabilizer is electrically connected with the third output end of the reference voltage generator;
the input end of the voltage control circuit is electrically connected with the third output end of the reference voltage generator;
the first input end of the oscillating circuit is electrically connected with the output end of the first voltage stabilizer, the second input end of the oscillating circuit is electrically connected with the output end of the second voltage stabilizer, and the third input end of the oscillating circuit is electrically connected with the output end of the voltage control circuit.
In a third aspect, an embodiment of the present invention further provides an electronic device, including: an oscillation generating circuit according to any embodiment of the present invention.
According to the embodiment of the invention, the voltage source with temperature compensation and the threshold compensation circuit are arranged in the filter, the input end of the threshold compensation circuit is electrically connected with the output end of the voltage source with temperature compensation, and the output end of the threshold compensation circuit is electrically connected with the control end of the filter circuit, so that the control voltage input to the control end of the filter circuit is the voltage subjected to temperature compensation and threshold compensation. Compared with the prior art, the MOS tube in the filter circuit is not influenced by Process angle, voltage and Temperature (PVT) changes by adding Temperature and threshold compensation to the MOS tube in the filter circuit, namely, the MOS tube is stabilized at PVT, so that noise filtering can keep optimal performance in different environments, interference existing in the filter is reduced, the filtering effect of the filter is improved, phase noise of the oscillation generating circuit is reduced, and the stability of phase noise performance of the oscillation generating circuit in different environments is improved. On the basis, on one hand, the embodiment of the invention can realize effective filtering by adopting the universal MOS tube, thereby reducing the production cost of the filter; on the other hand, the embodiment of the invention avoids adopting an external compensation circuit to meet the requirement of a high-performance oscillation generating circuit, and can be integrated on one IC chip, thereby improving the competitiveness of high-end oscillator products.
Drawings
Fig. 1 is a schematic structural diagram of a filter according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a threshold compensation circuit according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a voltage source with temperature compensation according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a filter according to an embodiment of the present invention;
fig. 5 is an equivalent circuit schematic diagram of a filter circuit according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a filter frequency response of a filter according to an embodiment of the present invention;
FIG. 7 is a schematic diagram showing a filtering frequency response of another filter according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of a filtering frequency response of another filter according to an embodiment of the present invention;
FIG. 9 is a schematic diagram showing a filtering frequency response of another filter according to an embodiment of the present invention;
FIG. 10 is a schematic diagram showing a filtering frequency response of another filter according to an embodiment of the present invention;
fig. 11 is a schematic diagram of an oscillation generating circuit according to an embodiment of the present invention;
fig. 12 is a schematic diagram of a noise spectrum of an output of an oscillation generating circuit according to an embodiment of the present invention;
FIG. 13 is a schematic diagram of a noise spectrum of an output of another oscillation generating circuit according to an embodiment of the present invention;
FIG. 14 is a schematic diagram of a noise spectrum of an output of an oscillation generating circuit according to an embodiment of the present invention;
fig. 15 is a schematic diagram of another oscillation generating circuit according to an embodiment of the present invention.
Detailed Description
The invention is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting thereof. It should be further noted that, for convenience of description, only some, but not all of the structures related to the present invention are shown in the drawings.
Fig. 1 is a schematic structural diagram of a filter according to an embodiment of the present invention. Referring to fig. 1, the filter can be applied to an on-chip integrated circuit, and particularly can be applied to a structure of a CMOS oscillation generating circuit. The filter includes: a filter circuit 110, a voltage source 120 with temperature compensation, and a threshold compensation circuit 130. The filter circuit 110 includes a plurality of MOS transistors (not shown in fig. 1), a voltage input terminal 111, a control terminal 112, and a voltage output terminal 113, wherein gates of the MOS transistors are electrically connected to the control terminal 112, the voltage input terminal 111 serves as an input terminal of the filter, and the voltage output terminal 113 serves as an output terminal of the filter. An input of the threshold compensation circuit 130 is electrically connected to an output of the voltage source 120 with temperature compensation, and an output of the threshold compensation circuit 130 is electrically connected to the control terminal 112 of the filter circuit 110.
The multiple MOS transistors in the filter circuit 110 are used as resistors in the filter circuit 110, the control end 112 of the filter circuit 110 is used for adjusting the resistance values of the multiple MOS transistors according to the control signal output by the threshold compensation circuit 130, so as to adjust the filtering function of the filter, and the filter circuit 110 is used for filtering the voltage input by the voltage input end 111 thereof and outputting the filtered voltage through the voltage output end 113. The filter circuit 110 may include, for example, a MOSFET-C filter circuit 110, where the MOSFET-C filter circuit 110 includes a plurality of transistors that are turned on and off by a control terminal 112 of the filter circuit 110 to control a filtering effect of the filter circuit 110. The voltage source 120 with temperature compensation is used for performing temperature compensation on the MOS transistor in the filter circuit 110, generating a voltage with temperature compensation, and outputting the voltage through an output terminal thereof. The voltage source 120 with temperature compensation may include, for example, a PTAT (Proportional to Absolute Temperature) circuit, with the voltage output by the PTAT circuit being linear with temperature. The threshold compensation circuit 130 is used for performing threshold compensation on the MOS transistor in the filter circuit 110. The output end of the threshold compensation circuit 130 is electrically connected with the gate of the MOS tube in the filter circuit 110, and the gate voltage of the MOS tube comprises a voltage with temperature compensation and a voltage with threshold compensation, so that the MOS tube in the filter circuit 110 is not affected by temperature and threshold.
In the embodiment of the invention, a voltage source 120 with temperature compensation and a threshold compensation circuit 130 are arranged in a filter, the input end of the threshold compensation circuit 130 is electrically connected with the output end of the voltage source 120 with temperature compensation, and the output end of the threshold compensation circuit 130 is electrically connected with the control end 112 of the filter circuit 110, so that the control voltage input to the control end 112 of the filter circuit 110 is the voltage subjected to temperature compensation and threshold compensation. Compared with the prior art, the MOS tube in the filter circuit 110 is subjected to temperature and threshold compensation, so that the MOS tube in the filter circuit 110 is not influenced by changes of process angles, voltage and temperature PVT, namely, the MOS tube is stabilized in PVT, noise filtering can keep optimal performance in different environments, interference existing in the filter is reduced, the filtering effect of the filter is improved, phase noise of the oscillation generating circuit is reduced, and stability of phase noise performance of the oscillation generating circuit in different environments is improved. On the basis, on one hand, the embodiment of the invention can realize effective filtering by adopting the universal MOS tube, thereby reducing the production cost of the filter; on the other hand, the embodiment of the invention avoids adopting an external compensation circuit to meet the requirement of a high-performance oscillation generating circuit, and can be integrated on one IC chip, thereby improving the competitiveness of high-end oscillator products.
Fig. 2 is a schematic diagram of a threshold compensation circuit according to an embodiment of the present invention. Referring to fig. 2, the threshold compensation circuit 130 may optionally include: a current source I1, a first current mirror MIR1 and a first transistor M1. The first end of the current source I1 is electrically connected with a first power supply; the first input end and the control end 112 of the first current mirror MIR1 are electrically connected with the second end of the current source I1, the second input end of the first current mirror MIR1 is electrically connected with the control end 112 of the filter circuit 110, and the first output end and the second output end of the first current mirror MIR1 are electrically connected with the second power supply; the first terminal of the first transistor M1 is electrically connected to the input terminal of the threshold compensation circuit 130, and the control terminal 112 and the second terminal are electrically connected to the control terminal 112 of the filter circuit 110.
Based on the above embodiments, optionally, the first transistor M1 is a MOS transistor.
The following describes the principle of threshold compensation of the MOS transistor according to the embodiment of the present invention. Since the threshold compensation circuit 130 is supplied with the output voltage VT of the voltage source 120 with temperature compensation, the current I is fixed D The following relationship exists:
VG＝VT-V gs2 (2)
wherein V is th ' is the threshold voltage of the first transistor.
Substituting equation (1) into equation (2) to obtain the output voltage of the threshold compensation circuit 130 as:
in the method, in the process of the invention,at a constant value, VG has a value proportional to temperature, less a threshold electricityPressure and a fixed constant value.
The control voltage VG output by the threshold compensation circuit 130 to the gate of the MOS transistor in the filter circuit 110 is as follows:
VG＝VPTAP-V th ′+V dC (4)
wherein V is dC Is a constant value.
The resistance formula of the MOS tube is as follows:
the formula for conductivity G is as follows:
G＝μC ox W/L(V gs -V th ) (6)
if the gate voltage of the MOS transistor is VG and the voltage input to the voltage input terminal 111 of the filter circuit 110 is VS, the formula of the conductivity G is as follows:
G＝μC ox W/L(VS-VG-V th ) (7)
in the formula, VG and V th All are parameters associated with temperature, equation (7) can be written as follows:
G＝μC ox W/L(VS-VG-V th (T)) (8)
in the MOS transistor, threshold voltage V th The relationship of (T) to temperature is as follows:
V th (T)＝V th (T 0 )-β(T-T 0 ) (9)
wherein T is 0 Is the reference temperature, beta is the temperature coefficient of the threshold voltage value of the MOS tube, and beta is a positive value.
Substituting equation (4) into equation (8) yields the conductivity G as follows:
G＝μC ox W/L(VS-VPTAP+V th ′(T)-V th (T)-V dC ) (10)
where VPTAP is the voltage output by voltage source 120 with temperature compensation, vptap=vt,
threshold voltage V of MOS tube is calculated according to formula (9) th (T) and threshold voltage V of MOS transistor for compensation th Substitution of' (T) yields the following formula:
G＝μC ox W/L(VS-VPTAP+(β-β′)(T-T 0 )-V dC ) (11)
as can be seen from equation (11), V is related to the process corner th (T 0 ) Is counteracted.
Alternatively, the VPTAP portion is designed as the following formula:
VPTAP＝Δβ×T (12)
wherein the voltage of VPTAP is linearly dependent on temperature, so that (beta-beta') (T-T) in formula (11) can be used 0 ) Partial cancellation causes the conductivity G to maintain a more or less fixed value at different temperatures and different threshold voltages of the process corner, thereby yielding the following formula:
G＝μC ox W/L×(VS+k′) (13)
wherein k' = -V dC -Δβ×T 0 Is a constant value.
Therefore, the conductivity G, i.e. the resistance R, of the MOS transistor in the filter circuit 110 provided by the embodiment of the invention is only related to the physical size W/L of the MOS transistor and the input voltage, so that the on-chip filter cut-off frequency can be ensured to maintain stable performance under the temperature and process changes, and the overall noise control is improved.
Fig. 3 is a schematic structural diagram of a voltage source with temperature compensation according to an embodiment of the present invention. Referring to fig. 3, optionally, the voltage source 120 with temperature compensation includes, based on the above embodiments: the second current mirror MIR2, the third current mirror MIR3, the first resistor R1, the second transistor M2, the third transistor M3, and the second resistor R2. The first input end, the second input end and the third input end of the second current mirror MIR2 are electrically connected with a first power supply, and the first output end of the second current mirror MIR2 is electrically connected with the output end of a voltage source 120 with temperature compensation; the first input end and the control end 112 of the third current mirror MIR3 are electrically connected with the second output end of the second current mirror MIR2, and the third output end and the control end 112 of the second current mirror MIR2 are electrically connected with the second input end of the third current mirror MIR 3; the first end of the first resistor R1 is electrically connected with the second output end of the third current mirror MIR 3; the first end of the second transistor M2 is electrically connected with the second end of the first resistor R1, and the second end and the control end 112 of the second transistor M2 are electrically connected with a second power supply; a first end of the third transistor M3 is electrically connected to the first output end of the third current mirror MIR3, and a second end and the control end 112 of the third transistor M3 are both electrically connected to the second power supply; the first terminal of the second resistor R2 is electrically connected to the output terminal of the voltage source 120 with temperature compensation, and the second terminal is electrically connected to the second power source.
Alternatively, the second transistor M2 and the third transistor M3 are two-stage junction transistors (Bipolar Junction Transistor, BJT) based on the above embodiments.
The voltage source 120 with temperature compensation provided in the embodiment of the present invention is a PTAT circuit, and the output voltage thereof is as follows:
wherein, N is the proportion of BJT connected by two groups of diodes, and the output voltage VT is in linear relation with temperature.
Fig. 4 is a schematic structural diagram of a filter according to an embodiment of the present invention, and fig. 5 is an equivalent circuit schematic diagram of a filter circuit according to an embodiment of the present invention. Referring to fig. 4, optionally, the filtering circuit 110 includes: at least two fourth transistors M4 and a fifth transistor M5. At least two fourth transistors M4 are connected in series between the voltage input terminal 111 and the voltage output terminal 113 of the filter circuit 110; the control terminal 112 of the fifth transistor M5 is electrically connected to the voltage output terminal 113 of the filter circuit 110, and the first terminal and the second terminal are electrically connected to the second power supply.
The filter circuit 110 in fig. 5 is a MOSFET-C filter circuit 110, and the filter circuit 110 in fig. 4 is equivalent to the filter circuit 110 in fig. 5. Illustratively, the plurality of fourth transistors M4 are equivalent in series to the resistor RL and the fifth transistor M5 is equivalent to the capacitor CL. In the filter circuit 110, if the bandwidth of the low-band filter circuit 110 is-3 dB, the frequency is 0.037Hz, the capacitance is 50pF, and the resistance is gΩ level. If the filter circuit 110 employs the resistor device shown in fig. 5, the filter circuit 110 is built in the IC chip, and the layout area required is large. According to the embodiment of the invention, the MOS tube is adopted to replace the resistor, and the L/W ratio (such as L/W=50 mu/0.3 mu) of the MOS tube can be designed to be larger, so that the equivalent resistance value of the MOS tube is improved, for example, the filter circuit 110 can occupy only about 0.035mm & lt 2 & gt area on a 0.18 mu M CMOS process, and the realized equivalent resistance value can be in the range of hundreds of MΩ to several GΩ. Compared with the scheme of increasing capacitance in the prior art, the embodiment of the invention can obviously reduce the PCB area and the quantity of Bill of materials (BOM). And the embodiment of the invention adopts the voltage source 120 with temperature compensation and the threshold compensation circuit 130, thereby avoiding that the equivalent resistance of the MOS tube is subjected to temperature and process deviation and different noise performances of different process corners (process corners), influencing the cut-off frequency (cutoff frequency) of filtering, avoiding different jitter performances of an oscillating signal at different temperatures, and realizing ultralow frequency filtering by adopting the MOSFET-C filter circuit 110 on a chip.
With continued reference to fig. 4, the filtering circuit 110 may further include: the sixth transistor M6, the sixth transistor M6 is connected in series between the voltage input terminal 111 and the voltage output terminal 113 of the filter circuit 110, and the control terminal 112 of the sixth transistor M6 inputs the enable signal.
The sixth transistor M6 is a bypass switch, and the sixth transistor M6 is configured to short-circuit the equivalent resistor in the filter circuit 110 when the power supply circuit is started, and provide a fast starting path to charge the bias capacitor, so that the starting time of other circuits is not slowed down due to the charging of the filter circuit 110. When the output of the LDO voltage stabilizer in the oscillation generating circuit reaches a certain voltage, the sixth transistor M6 is turned on by a simple circuit such as comparator output control, and then the function of low-frequency filtering can be achieved.
Optionally, the filter circuit 110 further includes an inverter and a seventh transistor, the seventh transistor and the sixth transistor M6 are connected in parallel, an enable signal is input to an input terminal of the inverter, and an output terminal of the inverter is electrically connected to a control terminal 112 of the seventh transistor.
Fig. 6 is a schematic diagram of a filter frequency response of a filter according to an embodiment of the present invention, fig. 7 is a schematic diagram of a filter frequency response of another filter according to an embodiment of the present invention, and fig. 8 is a schematic diagram of a filter frequency response of another filter according to an embodiment of the present invention. Specifically, fig. 6 is a schematic diagram of a filtered frequency response of a filtered cutoff frequency with temperature change at a single process corner when both a voltage source with temperature compensation and a threshold compensation circuit are turned off; FIG. 7 is a graph showing the filtered frequency response of the filtered cut-off frequency with different process angles (FF, TT and SS process angles, respectively) at the same temperature when both the voltage source with temperature compensation and the threshold compensation circuit are off; fig. 8 is a graph showing the filtered cut-off frequency as a function of temperature and different process angles (FF, TT and SS process angles, respectively) when both the voltage source with temperature compensation and the threshold compensation circuit are off. Referring to fig. 6-8, the cut-off frequency of the filtering varies greatly as temperature changes at a single process corner when both the voltage source with temperature compensation and the threshold compensation circuit are off. The noise attenuation change range at 1KHz is-60 dB to-93 dB, and the change range is greatly changed; the filter frequency response at the same temperature (example 25 ℃) but at different process angles varies greatly with the degree of noise reduction at 1 kHz; the variation in noise attenuation at 1kHz ranges from-49 dB to-95 dB, and this 46dB difference is difficult to grasp for the noise control of the oscillator circuit.
Fig. 9 is a schematic diagram of a filtering frequency response of another filter according to an embodiment of the present invention. Referring to fig. 9, when both the voltage source with temperature compensation and the threshold compensation circuit are turned on, it can be seen that the filtering frequency response is more stable with different temperature changes and different process angles, and the change at 1kHz is only about 5dB, so that the stability of noise attenuation is greatly improved.
Fig. 10 is a schematic diagram of a filtering frequency response of another filter according to an embodiment of the present invention. Referring to fig. 10, it can be seen that the bypass switch is turned on after the bypass switch (sixth transistor) is turned on, as compared with the bypass switch which is not turned on. The frequency response of the filter circuit changes from a few MHz to a few Hz when the-3 dB bandwidth is shorted out of the resistor.
The embodiment of the invention also provides an oscillation generating circuit. Fig. 11 is a schematic diagram of an oscillation generating circuit according to an embodiment of the present invention. Referring to fig. 11, the oscillation generating circuit includes: a reference source 200, a filter 100 according to any of claims 1-8, a reference voltage generator 300, a first voltage regulator 400, a second voltage regulator 500, a voltage control circuit 600, an oscillating circuit 700. The input end of the filter 100 is electrically connected with the output end of the reference source 200; the input end of the reference voltage generator 300 is electrically connected with the output end of the filter 100; a first input terminal of the first voltage regulator 400 is electrically connected to a first output terminal of the reference voltage generator 300, and a second input terminal of the reference voltage generator 300 is electrically connected to a second output terminal of the reference voltage generator 300; the input end of the second voltage stabilizer 500 is electrically connected with the third output end of the reference voltage generator 300; an input terminal of the voltage control circuit 600 is electrically connected to a third output terminal of the reference voltage generator 300; a first input terminal of the oscillating circuit 700 is electrically connected to the output terminal of the first voltage regulator 400, a second input terminal of the oscillating circuit 700 is electrically connected to the output terminal of the second voltage regulator 500, and a third input terminal of the oscillating circuit 700 is electrically connected to the output terminal of the voltage control circuit 600.
The reference source 200 may be, for example, a bandgap reference (band gap), the first voltage regulator 400 may be, for example, an LDO voltage regulator, and the second voltage regulator 500 provides a bias voltage to the oscillating circuit 700. The oscillating circuit 700 includes a sustaining amplifier and a resonator, which may be a crystal resonator or a MEMS resonator. The most influencing the phase noise of the oscillator is the bandgap reference, which provides the reference voltage and bias current to the oscillating portion. The embodiment of the invention starts from the source path of noise and interference of the oscillation generating circuit, the filter 100 is arranged between the band gap reference and the reference voltage generator 300 to solve the problem of phase noise from the source, the output voltage of the band gap reference is filtered by the filter 100, and the reference voltage is cleaner, so that the output of the reference voltage generator 300, the output of the first voltage stabilizer 400, the output of the second voltage stabilizer 500 and the output of the voltage control circuit 600 are all voltages passing through the filter 100 and are not influenced by the noise of the band gap reference, thereby reducing the power supply noise of the oscillation circuit 700 and directly improving the phase noise of the output.
In the embodiment of the invention, a voltage source with temperature compensation and a threshold compensation circuit are arranged in a filter of an oscillation generating circuit, the input end of the threshold compensation circuit is electrically connected with the output end of the voltage source with temperature compensation, and the output end of the threshold compensation circuit is electrically connected with the control end of the filter circuit, so that the control voltage input to the control end of the filter circuit is the voltage subjected to temperature compensation and threshold compensation. Compared with the prior art, the MOS tube in the filter circuit is enabled not to be influenced by process angle, voltage and temperature PVT changes by adding temperature and threshold compensation to the MOS tube in the filter circuit, namely, the MOS tube is stabilized at PVT, noise filtering can keep optimal performance in different environments, interference existing in the filter is reduced, the filtering effect of the filter is improved, phase noise of the oscillation generating circuit is reduced, and stability of phase noise performance of the oscillation generating circuit in different environments is improved. On the basis, on one hand, the embodiment of the invention can realize effective filtering by adopting the universal MOS tube, thereby reducing the production cost of the filter; on the other hand, the embodiment of the invention avoids adopting an external compensation circuit to meet the requirement of a high-performance oscillation generating circuit, and can be integrated on one IC chip, thereby improving the competitiveness of high-end oscillator products.
Fig. 12 is a schematic diagram of a noise spectrum of an output of an oscillation generating circuit according to an embodiment of the present invention. Referring to fig. 12, in the absence of the added filter, noise is mainly flicker noise concentrated at low frequencies, and lower thermal noise covers the entire spectrum. After adding the filter, the noise has a significantly effective attenuation at low frequencies.
Fig. 13 is a schematic diagram of a noise spectrum of an output of another oscillation generating circuit according to an embodiment of the present invention. Fig. 14 is a schematic diagram of a noise spectrum of an output of an oscillation generating circuit according to an embodiment of the present invention. Specifically, FIG. 13 is a graph of phase noise at 1kHz versus 130.4928dB for a MEMS oscillator with and without a filter, when the filter is not on; when the filter is on, the phase noise at 1kHz is-137.1784 dBc/Hz. FIG. 14 is a graph showing phase noise at 1kHz versus 147.8553dB for a crystal oscillator with and without a filter, when the filter is not on; when the filter is on, the phase noise at 1kHz is-152.3066 dBc/Hz. As a result, the phase noise was improved by 4 to 6dB at 1kHz and 15 to 20dB at 10Hz and 100Hz when the filter was present, as compared with the filter without the filter.
Fig. 15 is a schematic diagram of another oscillation generating circuit according to an embodiment of the present invention. Referring to fig. 15, unlike the oscillation generating circuit in fig. 11, the filter 100 of the oscillation generating circuit is disposed between the reference source 200 and the first voltage regulator 400. The voltage output from the first voltage regulator 400 is not affected by noise of the bandgap reference.
The embodiment of the invention also provides an electronic device. The electronic device includes: oscillation generating circuits as provided by any of the embodiments of the present invention. The electronic device may be, for example, an oscillator, which may be a crystal oscillator or a MEMS oscillator.
In the embodiment of the invention, a voltage source with temperature compensation and a threshold compensation circuit are arranged in a filter of an oscillator, the input end of the threshold compensation circuit is electrically connected with the output end of the voltage source with temperature compensation, and the output end of the threshold compensation circuit is electrically connected with the control end of the filter circuit, so that the control voltage input to the control end of the filter circuit is the voltage subjected to temperature compensation and threshold compensation. Compared with the prior art, the MOS tube in the filter circuit is enabled not to be influenced by process angle, voltage and temperature PVT changes by adding temperature and threshold compensation to the MOS tube in the filter circuit, namely, the MOS tube is stabilized at PVT, noise filtering can keep optimal performance in different environments, interference existing in the filter is reduced, the filtering effect of the filter is improved, phase noise of the oscillation generating circuit is reduced, and stability of phase noise performance of the oscillation generating circuit in different environments is improved. On the basis, on one hand, the embodiment of the invention can realize effective filtering by adopting the universal MOS tube, thereby reducing the production cost of the filter; on the other hand, the embodiment of the invention avoids adopting an external compensation circuit to meet the requirement of a high-performance oscillation generating circuit, and can be integrated on one IC chip, thereby improving the competitiveness of high-end oscillator products.
Note that the above is only a preferred embodiment of the present invention and the technical principle applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, while the invention has been described in connection with the above embodiments, the invention is not limited to the embodiments, but may be embodied in many other equivalent forms without departing from the spirit or scope of the invention, which is set forth in the following claims.
Claims (7)
1. A filter, comprising:
the filter circuit comprises a plurality of MOS tubes, a voltage input end, a control end and a voltage output end, wherein the grid electrodes of the MOS tubes are electrically connected with the control end, the voltage input end is used as the input end of the filter, and the voltage output end is used as the output end of the filter;
the voltage source with temperature compensation and the threshold compensation circuit are arranged, the input end of the threshold compensation circuit is electrically connected with the output end of the voltage source with temperature compensation, and the output end of the threshold compensation circuit is electrically connected with the control end of the filter circuit;
the threshold compensation circuit includes:
the first end of the current source is electrically connected with the first power supply;
the first input end and the control end of the first current mirror are electrically connected with the second end of the current source, the second input end of the first current mirror is electrically connected with the control end of the filter circuit, and the first output end and the second output end of the first current mirror are electrically connected with the second power supply;
the first end of the first transistor is electrically connected with the input end of the threshold compensation circuit, and the control end and the second end of the first transistor are electrically connected with the control end of the filter circuit;
the voltage source with temperature compensation includes:
the first input end, the second input end and the third input end of the second current mirror are electrically connected with a first power supply, and the first output end of the second current mirror is electrically connected with the output end of the voltage source with temperature compensation;
the first input end and the control end of the third current mirror are electrically connected with the second output end of the second current mirror, and the third output end and the control end of the second current mirror are electrically connected with the second input end of the third current mirror;
a first resistor, wherein a first end of the first resistor is electrically connected with a second output end of the third current mirror;
a second transistor, wherein a first end of the second transistor is electrically connected with a second end of the first resistor, and a second end and a control end of the second transistor are electrically connected with a second power supply;
a third transistor, a first end of which is electrically connected with a first output end of the third current mirror, and a second end and a control end of which are electrically connected with the second power supply;
and the first end of the second resistor is electrically connected with the output end of the voltage source with temperature compensation, and the second end of the second resistor is electrically connected with the second power supply.
2. The filter of claim 1, wherein the first transistor is a MOS transistor.
3. The filter of claim 1, wherein the second transistor and the third transistor are two-stage junction transistors.
4. The filter of claim 1, wherein the filter circuit comprises:
at least two fourth transistors connected in series between a voltage input terminal and a voltage output terminal of the filter circuit;
and the control end of the fifth transistor is electrically connected with the voltage output end of the filter circuit, and the first end and the second end are electrically connected with a second power supply.
5. The filter of claim 4, wherein the filter circuit further comprises:
and a sixth transistor connected in series between the voltage input terminal and the voltage output terminal of the filter circuit, the control terminal of the sixth transistor inputting an enable signal.
6. An oscillation generating circuit, comprising:
a reference source;
a filter as claimed in any one of claims 1 to 5, the input of the filter being electrically connected to the output of the reference source;
the input end of the reference voltage generator is electrically connected with the output end of the filter;
the first input end of the first voltage stabilizer is electrically connected with the first output end of the reference voltage generator, and the second input end of the reference voltage generator is electrically connected with the second output end of the reference voltage generator;
the input end of the second voltage stabilizer is electrically connected with the third output end of the reference voltage generator;
the input end of the voltage control circuit is electrically connected with the third output end of the reference voltage generator;
the first input end of the oscillating circuit is electrically connected with the output end of the first voltage stabilizer, the second input end of the oscillating circuit is electrically connected with the output end of the second voltage stabilizer, and the third input end of the oscillating circuit is electrically connected with the output end of the voltage control circuit.
7. An electronic device, comprising: the oscillation generating circuit of claim 6.
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| CN201910165185.4A CN109756204B (en) | 2019-03-05 | 2019-03-05 | Filter, oscillation generating circuit and electronic device |
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