CN213906643U - Self-reference RC oscillator - Google Patents
Self-reference RC oscillator Download PDFInfo
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- CN213906643U CN213906643U CN202120100917.4U CN202120100917U CN213906643U CN 213906643 U CN213906643 U CN 213906643U CN 202120100917 U CN202120100917 U CN 202120100917U CN 213906643 U CN213906643 U CN 213906643U
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Abstract
The utility model relates to a self-reference RC oscillator, which comprises an annular oscillator and two equal-voltage output circuits outputting two paths of same voltage; one output of the equal voltage output circuit is connected with the ring oscillator, and the other output of the equal voltage output circuit is connected to the ring oscillator after being connected with a resistor in series. The utility model discloses simple structure, oscillation frequency precision are high, do not need complicated reference current and basic voltage and comparator module, and the design is simple, low cost.
Description
Technical Field
The utility model relates to an oscillator technical field especially relates to a from benchmark RC oscillator.
Background
An on-chip oscillator is typically used in SOC systems to provide a clock with a low frequency drift with temperature. The RC oscillator is widely used due to its simple structure and high integration. With the progress of technology, the requirements on oscillators are higher and higher, and the temperature stability is improved while the cost is reduced.
As shown in fig. 1, a conventional RC oscillator generally includes a reference voltage module, a charge and discharge control module, a comparator, and an RS flip-flop. The charge and discharge control circuit controls the charge and discharge of the capacitor by the reference voltage, the comparator compares the voltage of the capacitor with the reference voltage and sends deaf the voltage to the charge and discharge control circuit, in order to obtain the oscillation frequency with low temperature drift, the voltage is required to be designed to be independent of the power voltage and the temperature, and the reference voltage is not influenced by the power voltage and the temperature. Because the reference voltage with low temperature drift is difficult to realize, and the offset voltage of the comparator also changes along with the temperature, the cost and the temperature characteristic of the traditional RC oscillator are difficult to improve, and the traditional RC oscillator with the structure has a complex structure, the precision of the traditional RC oscillator is influenced by the precision of the reference voltage module, the precision of the reference voltage 1, the precision of the reference voltage 2 and the precision of the comparator, the design difficulty is high, and the manufacturing cost is high.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to overcome prior art's shortcoming, provide a from benchmark RC oscillator, solved not enough that traditional RC oscillator exists.
The purpose of the utility model is realized through the following technical scheme: a self-reference RC oscillator comprises a ring oscillator and an equal-voltage output circuit for outputting two paths of same voltage; one output of the equal voltage output circuit is connected with the ring oscillator, and the other output of the equal voltage output circuit is connected to the ring oscillator after being connected with a resistor in series.
The ring oscillator comprises a plurality of stages of phase inverters connected in parallel in sequence, and each stage of phase inverter comprises two mos tubes connected in series; one output of the equal-voltage output circuit is connected with one ends of the two mos tubes connected in series, and the other output of the equal-voltage output circuit is connected with the other ends of the two mos tubes connected in series after being connected with a resistor in series; the serial ends of the two mos tubes in the phase inverters at each stage are connected with each other, and the serial ends of the two mos tubes in the phase inverters at the two ends of the ring oscillator are connected with each other.
The equal voltage output circuit comprises mos tubes M1 and M2, wherein the grid electrode of the mos tube M1 is connected with the drain electrode and is connected with the grid electrode of the mos tube M2; the source electrode of the mos tube M1 is connected with the source electrode of the mos tube M2 and is connected with a VDD voltage end; the drain of the mos tube M1 is connected in series with a resistor to one end of the ring oscillator, and the mos tube M2 is connected to the other end of the ring oscillator.
The oscillator further comprises a D flip-flop and a Schmitt flip-flop, and the equal voltage output circuit comprises an operational amplifier circuit; the operational amplifier circuit outputs two paths of voltages with the same magnitude to the ring oscillator and is connected with the Q end of the D trigger; one end of the Schmitt trigger is connected with the clock end of the ring oscillator, and the other end of the Schmitt trigger is connected with the clock end of the D trigger.
The operational amplifier circuit comprises an operational amplifier U1 and mos tubes M1, M2 and Ms; the grid electrode of the mos tube M1 is connected with the drain electrode and is connected with the grid electrode of the mos tube M2; the source electrode of the mos tube M1 is connected with the source electrode of the mos tube M2 and is connected with a VDD voltage end; the output end of the operational amplifier U1 is connected with the gates of the mos tubes M1 and M2, the positive input end of the operational amplifier U1 is connected with the drain electrode of the mos tube M2 and one end of the ring oscillator, and the negative input end of the operational amplifier U1 is connected with the drain electrode of the mos tube M1; the source electrode of the mos tube Ms is connected with the grid electrodes of the mos tubes M1 and M2, the drain electrode of the mos tube Ms is connected with the negative input end of the operational amplifier U1, and the grid electrode of the mos tube Ms is connected with the Q end of the D trigger.
The utility model has the advantages of it is following: a self-reference RC oscillator has the advantages of simple structure, high oscillation frequency precision, no need of complex reference current, basic voltage and a comparator module, simple design and low cost.
Drawings
FIG. 1 is a circuit diagram of a conventional RC oscillator;
fig. 2 is a circuit diagram of a first embodiment of the present invention;
fig. 3 is a circuit diagram of a second embodiment of the present invention;
fig. 4 is a circuit diagram of a third embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations. Thus, the detailed description of the embodiments of the present application provided below in connection with the appended drawings is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present application without making any creative effort, shall fall within the protection scope of the present application. The invention is further described below with reference to the accompanying drawings.
Example 1
As shown in fig. 2, a self-referenced RC oscillator includes an operational amplifier circuit, a ring oscillator, a D flip-flop, and a schmitt trigger; the ring oscillator comprises a plurality of stages of inverters connected in parallel in sequence, wherein each stage of inverter comprises two mos tubes connected in series; one output of the equal-voltage output circuit is connected with one ends of the two mos tubes connected in series, and the other output of the equal-voltage output circuit is connected with the other ends of the two mos tubes connected in series after being connected with a resistor R in series; the serial ends of the two mos tubes in the phase inverters at each stage are connected with each other, and the serial ends of the two mos tubes in the phase inverters at the two ends of the ring oscillator are connected with each other
An operational amplifier U1 and mos tubes M1, M2, Ms; the grid electrode of the mos tube M1 is connected with the drain electrode and is connected with the grid electrode of the mos tube M2; the source electrode of the mos tube M1 is connected with the source electrode of the mos tube M2 and is connected with a VDD voltage end; the output end of the operational amplifier U1 is connected with the gates of the mos tubes M1 and M2, the positive input end of the operational amplifier U1 is connected with the drain electrode of the mos tube M2 and one end of the ring oscillator, and the negative input end of the operational amplifier U1 is connected with the drain electrode of the mos tube M1; the source electrode of the mos tube Ms is connected with the grid electrodes of the mos tubes M1 and M2, the drain electrode of the mos tube Ms is connected with the negative input end of the operational amplifier U1, and the grid electrode of the mos tube Ms is connected with the Q end of the D trigger.
Under the action of an operational amplifier U1, the voltage of a node V1 is equal to the voltage of a node V2, the current I1 is equal to I2, and the current I1 is equal to V1/R; ring oscillator output frequency f formed by multi-stage invertersclkI2/V2 xc, where C is each inverter stageThe sum of the equivalent capacitances of; since I1-I2 and V1-V2, f isclkTherefore, the oscillation frequency of the low temperature drift can be realized by using the resistor with the low temperature drift as 1/R multiplied by C.
Since the points V1 and V2 can be stabilized at 0V after the circuit is started, which may result in the failure of the ring oscillator to operate normally, a schmitt trigger is connected in series with the output of the oscillator, the output of the schmitt trigger is connected to the clk terminal of the D trigger, the D terminal of the D trigger is connected to VDD, and the output terminal of the D trigger is connected to the gate of the start tube Ms. When V1 and V2 are 0V, the output of the ring oscillator is 0, the output of Schmitt is VDD, the output Q of the D flip-flop is 0V, the Ms tube is conducted, the V1 node is pulled to VDD, V2 is also pulled to VDD under the action of the amplifier U1, at the moment, the ring oscillator starts to oscillate, when the output of the oscillator is inverted from VDD to 0V, the output of the Schmitt flip-flop is inverted from 0V to VDD, the output Q of the D flip-flop is inverted from 0V to VDD, at the moment, the Ms stops conducting, and the circuit starts.
Example 2
As shown in fig. 3, the present embodiment is different from embodiment 1 in that a chopper operational amplifier is used as the operational amplifier U1; due to device mismatch, the operational amplifier has an offset voltage Vos, which is usually several mV or even several tens mV in CMOS, and the Vos causes the node voltages of V1 and V2 to be unequal, which in turn causes the frequency and design deviation of the oscillator. In order to further improve the output frequency precision of the oscillator, the operational amplifier is designed into a chopping operational amplifier by utilizing the characteristic that the circuit has a clock. The chopping technology can reduce the offset to the level of 10uV, and the output frequency of the oscillator is greatly improved.
Example 3
As shown in fig. 4, in this embodiment, the operational amplifier circuits in embodiments 2 and 3 may be replaced by a mirror relationship between mos transistors M1 and M2, such that I1 is equal to I2, and I1 is equal to V1/R, and a D flip-flop and a schmitt flip-flop are not required in this embodiment; ring oscillator output frequency f consisting of multi-stage invertersclkI2/V2 xc; wherein C is the sum of equivalent capacitances of inverters at all levels; since I1-I2 and V1-V2, f isclk1/R × C, therefore a low temperature drift is usedThe low temperature drift oscillation frequency can be realized by the resistor. Since the M1 tube and the resistor R form a voltage division relation in the circuit, the structure can work normally without starting the circuit.
The foregoing is illustrative of the preferred embodiments of this invention, and it is to be understood that the invention is not limited to the precise form disclosed herein and that various other combinations, modifications, and environments may be resorted to, falling within the scope of the concept as disclosed herein, either as described above or as apparent to those skilled in the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (5)
1. A self-referenced RC oscillator, characterized by: the voltage-equalizing circuit comprises a ring oscillator and two equal-voltage output circuits which output two paths of equal voltages with the same voltage; one output of the equal voltage output circuit is connected with the ring oscillator, and the other output of the equal voltage output circuit is connected to the ring oscillator after being connected with a resistor in series.
2. A self-reference RC oscillator as claimed in claim 1, wherein: the ring oscillator comprises a plurality of stages of phase inverters connected in parallel in sequence, and each stage of phase inverter comprises two mos tubes connected in series; one output of the equal-voltage output circuit is connected with one ends of the two mos tubes connected in series, and the other output of the equal-voltage output circuit is connected with the other ends of the two mos tubes connected in series after being connected with a resistor in series; the serial ends of the two mos tubes in the phase inverters at each stage are connected with each other, and the serial ends of the two mos tubes in the phase inverters at the two ends of the ring oscillator are connected with each other.
3. A self-reference RC oscillator as claimed in claim 2, wherein: the equal voltage output circuit comprises mos tubes M1 and M2, wherein the grid electrode of the mos tube M1 is connected with the drain electrode and is connected with the grid electrode of the mos tube M2; the source electrode of the mos tube M1 is connected with the source electrode of the mos tube M2 and is connected with a VDD voltage end; the drain of the mos tube M1 is connected in series with a resistor to one end of the ring oscillator, and the mos tube M2 is connected to the other end of the ring oscillator.
4. A self-reference RC oscillator as claimed in claim 2, wherein: the oscillator further comprises a D flip-flop and a Schmitt flip-flop, and the equal voltage output circuit comprises an operational amplifier circuit; the operational amplifier circuit outputs two paths of voltages with the same magnitude to the ring oscillator and is connected with the Q end of the D trigger; one end of the Schmitt trigger is connected with the clock end of the ring oscillator, and the other end of the Schmitt trigger is connected with the clock end of the D trigger.
5. A self-reference RC oscillator as claimed in claim 4, wherein: the operational amplifier circuit comprises an operational amplifier U1 and mos tubes M1, M2 and Ms; the grid electrode of the mos tube M1 is connected with the drain electrode and is connected with the grid electrode of the mos tube M2; the source electrode of the mos tube M1 is connected with the source electrode of the mos tube M2 and is connected with a VDD voltage end; the output end of the operational amplifier U1 is connected with the gates of the mos tubes M1 and M2, the positive input end of the operational amplifier U1 is connected with the drain electrode of the mos tube M2 and one end of the ring oscillator, and the negative input end of the operational amplifier U1 is connected with the drain electrode of the mos tube M1; the source electrode of the mos tube Ms is connected with the grid electrodes of the mos tubes M1 and M2, the drain electrode of the mos tube Ms is connected with the negative input end of the operational amplifier U1, and the grid electrode of the mos tube Ms is connected with the Q end of the D trigger.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202120100917.4U CN213906643U (en) | 2021-01-14 | 2021-01-14 | Self-reference RC oscillator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202120100917.4U CN213906643U (en) | 2021-01-14 | 2021-01-14 | Self-reference RC oscillator |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN213906643U true CN213906643U (en) | 2021-08-06 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202120100917.4U Active CN213906643U (en) | 2021-01-14 | 2021-01-14 | Self-reference RC oscillator |
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| CN (1) | CN213906643U (en) |
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2021
- 2021-01-14 CN CN202120100917.4U patent/CN213906643U/en active Active
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