The present invention relates to an oscillation circuit using an oscillator.
In recent years, a small electronic device with a wireless circuit such as a mobile phone or an IoT (Internet-Of-Things) device has required to prolong the life of a battery. Therefore, reduction of the power consumption of electronic circuits and electronic parts used in the device is an important technical issue.
Conventionally, a small electronic device has widely used an inverter-based Pierce oscillation circuit using a crystal oscillator shown in
The Pierce oscillation circuit has a simple arrangement, and thus has been used for a long time. However, the Pierce oscillation circuit cannot obtain a high voltage component for oscillation, and causes a current to regularly flow, resulting in high power consumption. In addition, the oscillation activation time of the Pierce oscillation circuit is long.
The present invention has been made to solve the above problems, and has as its object to provide an oscillation circuit that can implement low power consumption and high-speed oscillation activation.
An oscillation circuit according to the present invention includes a power supply terminal, a ground terminal, an oscillator, and an amplification circuit including a first capacitor and a second capacitor series-connected between two terminals of the oscillator, an input terminal connected to the oscillator and the first capacitor, an output terminal connected to the first capacitor and the second capacitor, a first n-type transistor having a source terminal connected to the output terminal, a drain terminal connected to a first switch connected to the power supply terminal, and a gate terminal connected to the input terminal, a first p-type transistor having a source terminal connected to the output terminal, a drain terminal connected to a second switch connected to the ground terminal, and a gate terminal connected to the input terminal, a second p-type transistor having a source terminal connected to the power supply terminal, a drain terminal connected to the input terminal and the gate terminal of the first n-type transistor, and a second n-type transistor having a source terminal connected to the ground terminal and a drain terminal connected to the input terminal and the gate terminal of the first p-type transistor.
In the above arrangement example of the oscillation circuit according to the present invention, the first switch connects the power supply terminal and the drain of the first n-type transistor at the time of an oscillation operation, and disconnects the power supply terminal and the drain of the first n-type transistor at the time of an oscillation stop, the second switch connects the ground terminal and the drain of the first p-type transistor at the time of the oscillation operation, and disconnects the ground terminal and the drain of the first p-type transistor at the time of the oscillation stop, the gate of the second p-type transistor is controlled to be turned off at the time of the oscillation operation and to be turned on at the time of the oscillation stop, and the gate of the second n-type transistor is controlled to be turned off at the time of the oscillation operation and to be turned on at the time of the oscillation stop.
An electronic device according to the present invention includes the above-described oscillation circuit.
According to the present invention, the gate terminal of the first n-type transistor of the amplification circuit is connected to a power supply voltage, when the second p-type transistor is ON, to feed back an output voltage of the amplification circuit to the gate terminal of the first n-type transistor via the first capacitor and a third capacitor, and the gate terminal of the first p-type transistor of the amplification circuit is connected to ground, when the second n-type transistor is ON, to feed back the output voltage of the amplification circuit to the gate terminal of the first p-type transistor via the first capacitor and a fourth capacitor, thereby making it possible to implement low power consumption and high-speed oscillation activation.
An embodiment of the present invention will be described below with reference to the accompanying drawings. First,
<Arrangement of Oscillation Circuit>
Based on the Colpitts oscillation circuit,
The amplification circuit A1 includes an NMOS transistor (n-type transistor) M1 having a source terminal connected to the output terminal of the amplification circuit A1, a PMOS transistor (p-type transistor) M2 having a source terminal connected to the output terminal of the amplification circuit A1, a PMOS transistor M3 having a gate terminal to which a bias reset signal
The capacitor Ccut1 is connected between the input terminal of the amplification circuit and the gate terminal of the NMOS transistor M1 and the drain terminal of the PMOS transistor M3. The capacitor Ccut2 is connected between the input terminal of the amplification circuit and the gate terminal of the PMOS transistor M2 and the drain terminal of the NMOS transistor M4. The capacitors Ccut1 and Ccut2 function as circuit parts that remove noise such as DC components. As the n-type transistors (M1 and M4) and the p-type transistors (M2 and M3), CMOS transistors may be used.
In the specification and claims of the present application, a case in which it is apparently described that “A and B are connected” includes a case in which A and B are electrically connected, a case in which A and B are functionally connected, and a case in which A and B are directly connected. In this case, A and B are target objects (for example, a device, an element, a circuit, a wiring, an electrode, a terminal, a conductive film, a layer, and the like). Therefore, a predetermined connection relationship is not limited to, for example, a connection relationship shown in a diagram or expressed in words, and includes a connection relationship other than the connection relationship shown in the diagram or expressed in words.
As a case in which A and B are electrically connected, for example, one or more elements (for example, a switch, a transistor, a capacitive element, an inductor, a resistive element, a diode, and the like) that can electrically connect A and B may be connected between A and B.
If an n-type or p-type transistor is used as a switch, the switch includes an input terminal (one of a source terminal and a drain terminal), an output terminal (one of the source terminal and the drain terminal), and a terminal (gate terminal) for controlling conduction. By applying a positive or negative voltage to the gate terminal, the transistor can control a current flowing from the input terminal to the output terminal, thereby functioning as a switch. If the switch is turned on, the two terminals of the switch are connected. On the other hand, if the switch is turned off, the two terminals of the switch are disconnected.
The NMOS transistor M1 and the PMOS transistor M2 form a cascode-connected complementary pair. The gate terminal of the NMOS transistor M1 is connected to the power supply voltage Vdd when the PMOS transistor M3 is turned on, and is fed back with the output voltage of the amplification circuit A1 via the capacitors C1 and Ccut1. The gate terminal of the PMOS transistor M2 is connected to ground when the NMOS transistor M4 is turned on, and is fed back with the output voltage of the amplification circuit A1 via the capacitors C1 and Ccut2.
<Operation of Oscillation Circuit>
The bias reset signals
Since high transconductance gm is required to activate oscillation, the bias reset signal
Furthermore, at the time of the oscillation stop, the oscillation permission signal EN is set at low, and the switches SW1 and SW2 are turned off. As the switches SW1 and SW2, for example, NMOS transistors can be used. The oscillation permission signal EN is input to the gate terminal of the NMOS transistor serving as the switch SW1 to connect the drain terminal to the power supply voltage Vdd and connect the source terminal to the drain terminal of the NMOS transistor M1. The oscillation permission signal EN is input to the gate terminal of the NMOS transistor serving as the switch SW2 to connect the drain terminal to the drain terminal of the PMOS transistor M2 and connect the source terminal to ground.
On the other hand, at the time of the oscillation operation, the bias reset signal
That is, if the PMOS transistor M3 is in the OFF state, a gate voltage VgN of the NMOS transistor M1 is biased by a voltage caused by the leakage current of the diode D1. Similarly, if the NMOS transistor M4 is in the OFF state, a gate voltage VgP of the PMOS transistor M2 is biased by a voltage caused by the leakage current of the diode D2. The resistor R1 indicates a resistance component through which the leakage current of the diode D1 flows, and the resistor R2 indicates a resistance component through which the leakage current of the diode D2 flows.
By exemplifying the PMOS transistor M3, the leakage current of the diode D1 always operates to raise the gate voltage VgN of the NMOS transistor M1 and maintain oscillation. If oscillation starts by a large signal, the gate terminal of the NMOS transistor M1 is dynamically biased by feedback from the output of the amplification circuit A1 via the capacitors C1 and Ccut1. However, the gate voltage VgN of the NMOS transistor M1 is clamped, by the diode D1, at a voltage value whose highest value is Vth3 Vdd (Vth3 is the threshold voltage of the PMOS transistor M3). Similarly, the gate voltage VgP of the PMOS transistor M2 is clamped, by the diode D2, at a voltage value whose lowest value is −Vth4 (Vth4 is the threshold voltage of the NMOS transistor M4).
Furthermore, at the time of the oscillation operation, the oscillation permission signal EN is set at high and the switches SW1 and SW2 are turned on.
<Oscillation Waveform of Oscillation Circuit>
For the purpose of comparison,
As is apparent from
<Phase Noise Characteristic of Oscillation Circuit>
<Oscillator in Oscillation Circuit>
As the oscillator X1 of the oscillation circuit, various oscillators such as a crystal oscillator and an oscillator using langasite-type piezoelectric single crystal can be used. To activate oscillation of the oscillation circuit at higher speed to implement lower oscillation activation energy, in this embodiment, an oscillator using langasite-type piezoelectric single crystal is used as the oscillator X1. There are various langasite-type piezoelectric single crystals but an oscillator using Ca3TaGa3Si2O14 (to be referred to as CTGS) is used in an experiment. Langasite is a single crystal expressed by a chemical composition such as Ca3NbGa3Si2O14 (to be referred to as CHGS), Ca3Ta(Ga1-XAlX)3Si2O14 (to be referred to as CTGAS), or Ca3Nb(Ga1-XAlX)3Si2O14 (to be referred to as CNGAS) in addition to CTGS, and the langasite-type piezoelectric single crystal is not limited to the oscillator using CTGS. In
As a result of the experiment using the CTGS oscillator as the oscillator X1, an oscillation activation time Ts of the oscillation circuit of this embodiment was 0.37 ms and oscillation activation energy Es was 30 nJ. On the other hand, if the crystal oscillator was used as the oscillator X1, the oscillation activation time Ts of the oscillation circuit shown in
Therefore, if the CTGS oscillator was used as the oscillator X1, it was confirmed that, as compared with a case in which the crystal oscillator was used, it was possible to implement the oscillation activation time earlier by about one order of magnitude, and also reduce the oscillation activation energy by about one order of magnitude, thereby implementing low power consumption.
As described above, according to this embodiment, it is possible to implement high-speed oscillation activation, and implement an oscillation circuit of low power consumption in the oscillation stationary state after oscillation activation.
Therefore, if the oscillation circuit of this embodiment is applied to, for example, an electronic device such as a mobile phone or an IoT device, this can contribute to implementation of an electronic device of low power consumption.
The present invention is applicable to an oscillation circuit used in a small electronic device. Explanation of the Reference Numerals and Signs
Number | Date | Country | Kind |
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2020-125663 | Jul 2020 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2021/017498 | 5/7/2021 | WO |