JP2015220584A - Oscillation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oscillation circuit which allows for fast start-up with low power consumption regardless of change in operation environment, variation in manufacturing process, or the specification of product.SOLUTION: An oscillation circuit 11 includes a resonator 12, and a negative resistance circuit, the negative resistance circuit includes a resistor 15, capacitors 13, 14, at least one first amplifier circuit 17_1-17_n including at least one transistor having a first size, and a second amplifier circuit 17_0 including at least one transistor having a second size equal to or less than the first size, and further includes a control section for operating at least the first amplifier circuit based on at least one of the operation environment and the process conditions, at the time of start-up, and operates only the second amplifier circuit after start-up.

Description

  Embodiments described herein relate generally to an oscillation circuit applied to, for example, a semiconductor device.

  For example, a wireless transmitter / receiver of a wireless sensor node (terminal device) and an oscillation circuit applied to an in-vehicle semiconductor device perform intermittent operation to reduce power consumption. In addition, an oscillation circuit that generates a clock signal for the microprocessor also achieves low power consumption. Although this type of oscillation circuit includes a resonator such as a crystal resonator, for example, this resonator has a long activation time, and it is difficult to activate the wireless transceiver at high speed.

  In an oscillation circuit using a crystal resonator, a technique for shortening the startup time has been developed (see, for example, Patent Document 1). Further, a technique has been developed in which an excitation signal is generated at the time of activation, and the activation time is shortened using the excitation signal (see, for example, Patent Document 2).

JP 2000-286637 A JP 2009-188738 A

  The present embodiment is intended to provide an oscillation circuit capable of starting at high speed with low power consumption regardless of changes in the operating environment, manufacturing process variations, or product specifications.

  The oscillation circuit of the present embodiment includes a resonator and a negative resistance circuit connected to the resonator. The negative resistance circuit includes a resistor and a capacitor connected to the resonator, and the resonance. At least one first amplifier circuit including at least one transistor having the first size and connected to the resonator, and at least one having a second size less than the first size and connected to the resonator A second amplifying circuit including two transistors, and at least the first amplifying circuit is operated based on at least one of an operating environment and a process condition at the time of starting, and only the second amplifying circuit after starting And a control unit for operating.

1 is a circuit diagram schematically showing an oscillation circuit according to a first embodiment. The circuit diagram which shows a part of FIG. 1 concretely. The figure shown in order to demonstrate operation | movement of 1st Embodiment. The figure which shows the relationship between the size of a transistor, and negative resistance (startup time). The figure which shows the relationship between the size ratio of a transistor, negative resistance, and consumption current. FIGS. 6A and 6B are diagrams illustrating simulation results of start-up times according to the first embodiment, in which FIG. 6A illustrates a case where the transistor size is small, and FIG. 6B illustrates a case where the transistor size is large. . The figure which shows the relationship between the size of a transistor, and negative resistance by making temperature into a parameter. The circuit diagram which shows roughly the oscillation circuit which concerns on 2nd Embodiment. FIG. 9 is a circuit diagram specifically showing a part of FIG. 8. FIG. 6 is a circuit diagram schematically showing an oscillation circuit according to a third embodiment. The figure which shows an example of the excitation circuit shown in FIG. 12A shows an example of an excitation signal output from the excitation circuit, FIG. 12B shows an operation of the excitation circuit, and FIG. 12C shows an operation of the oscillation circuit. It is. The figure which shows the simulation result at the time of using the oscillation circuit and excitation circuit which are shown in 3rd Embodiment.

  Hereinafter, embodiments will be described with reference to the drawings. In the drawings, the same parts are denoted by the same reference numerals.

(First embodiment)
FIG. 1 schematically shows an oscillation circuit 11 according to the first embodiment. The oscillation circuit 11 uses, for example, a crystal resonator as the resonator 12. However, it is not limited to a crystal resonator. One end of the resonator 12 is grounded via a capacitor 13, and the other end is grounded via a capacitor 14. Between the one end and the other end of the resonator 12, a feedback resistor 15 constituted by a fixed resistor and a variable amplifier circuit 17 are connected. These capacitors 13 and 14, the resistor 15, and the variable amplifier circuit 17 constitute a negative resistance circuit.

  The variable amplifier circuit 17 includes a plurality of amplifier circuits 17_0 and 17_1 to 17_n connected in parallel between both ends of the resonator 12. Each of the amplifier circuits 17_0 and 17_1 to 17_n includes, for example, one or more transistors. In the first embodiment, the amplifier circuits 17_0 and 17_1 to 17_n are mainly configured by, for example, CMOS inverter circuits. The CMOS inverter circuit includes, for example, a p-channel MOS transistor (hereinafter referred to as a pMOS transistor) P1 and an n-channel MOS transistor (hereinafter referred to as an nMOS transistor) N1.

  The amplifier circuits 17_0 and 17_1 to 17_n take into account current consumption during a steady operation described later, for example, the sizes of the pMOS transistor P1 and the nMOS transistor N1 constituting the amplifier circuit 17_0 are pMOS transistors constituting the amplifier circuits 17_1 to 17_n. It is set smaller than the size of P1 and nMOS transistor N1. Here, the size of the transistor means, for example, the channel width of the transistor.

  In other words, the transconductance gm of the amplifier circuits 17_1 to 17_n is set larger than the transconductance gm of the amplifier circuit 17_0.

  However, the present invention is not limited to this, and the pMOS transistors P1 constituting the CMOS inverter circuits of the amplifier circuits 17_0 and 17_1 to 17_n may have the same size, for example, and the nMOS transistors N1 may have the same size, for example. That is, the transconductances gm of the amplifier circuits 17_0 and 17_1 to 17_n may be made uniform.

  The amplifier circuits 17_0 and 17_1 to 17_n are connected to the control unit 18. The control unit 18 controls the amplifier circuits 17_0 and 17_1 to 17_n based on an operating environment such as temperature and power supply voltage and process conditions when the semiconductor device is manufactured. For this reason, for example, output signals from the temperature sensor 19, the voltage sensor 20, and the process condition setting unit 21 are supplied to the control unit 18.

  The temperature sensor 19 detects the temperature of a semiconductor chip (not shown) on which the oscillation circuit 11 is mounted, for example. The voltage sensor 20 detects a power supply voltage of, for example, a semiconductor chip on which the oscillation circuit 11 is mounted. The process condition setting unit 21 is, for example, a memory that holds information related to variations in the manufacturing process of, for example, a semiconductor chip on which the oscillation circuit 11 is mounted. The memory includes information related to process variations inspected at the time of manufacturing the semiconductor chip, for example. Is remembered.

  The control unit 18 selectively controls the amplifier circuits 17_0 and 17_1 to 17_n based on the output signals of the temperature sensor 19, the voltage sensor 20, and the process condition setting unit 21. Thus, by selectively driving the amplifier circuits 17_0 and 17_1 to 17_n, the size (or gm) of the transistor of the variable amplifier circuit 17 is changed, and the variable amplifier circuit 17, the resistor 15, and the capacitors 13 and 14 are configured. The negative resistance (amplification degree) is changed.

  Further, the control unit 18 detects the signal amplitude of the oscillation circuit 11 based on the output signal of the oscillation circuit 11, and when the signal amplitude reaches a specified value, changes the amplification circuit 17 to the size of the transistor in the steady state.

  FIG. 2 shows specific examples of the amplifier circuits 17_0 and 17_1 to 17_n and the control unit 18. The amplifier circuits 17_0 and 17_1 to 17_n are each configured by, for example, a three-state amplifier. Since the amplifier circuits 17_0 and 17_1 to 17_n have the same configuration, only the amplifier circuit 17_0 will be described.

  In the amplifier circuit 17_0, a pMOS transistor P2 is connected between the pMOS transistor P1 and a node to which the power supply VDD is supplied, and an nMOS transistor N2 is connected between the nMOS transistor N1 and the ground. The gate electrode of the pMOS transistor P2 is connected to the output terminal of the inverter circuit I1. The input terminal of the inverter circuit I1 and the gate electrode of the nMOS transistor N2 are connected to one output terminal of the control unit 18.

  The control unit 18 includes, for example, an amplitude detector 18a, a transistor size determiner 18b, and a selection signal generator 18c.

  The amplitude detector 18a is configured by, for example, an envelope detection circuit, and detects the amplitude of the signal output from the oscillation circuit 11. When the amplitude of the detected signal is larger than a predetermined threshold, the amplitude detector 18a determines that the oscillation circuit 11 has reached a steady state, and supplies, for example, a high level signal to the transistor size determiner 18b.

  The transistor size determiner 18b is supplied with the output signal of the amplitude detector 18a, the temperature sensor 19, the voltage sensor 20, and the output signal of the process condition setting unit 21.

  The transistor size determiner 18b outputs a signal for setting the size of the transistor constituting the variable amplifier circuit 17 in response to variations in the output signal, temperature, power supply voltage, and process conditions of the amplitude detector 18a. It is configured by a logic circuit. That is, the logic circuit outputs a plurality of so-called tables that output size information of the transistors constituting the variable amplifier circuit 17 corresponding to variations in the output signal, temperature, power supply voltage, and process conditions of the amplitude detector 18a. Is configured. The transistor size determiner 18b outputs a signal for setting the optimum transistor size based on the output signal of the amplitude detector 18a, the temperature sensor 19, the voltage sensor 20, and the output signal of the process condition setting unit 21. The output signal of the transistor size determiner 18b is supplied to the selection signal generator 18c.

  The selection signal generator 18c generates a signal for selecting the amplifier circuits 17_0 and 17_1 to 17_n based on the output signal of the transistor size determiner 18b. Specifically, in the amplifier circuits 17_0 and 17_1 to 17_n, when “n” is, for example, “7”, the selection signal generator 18c generates, for example, an 8-bit signal based on the output signal of the transistor size determiner 18b. Output. The amplifier circuits 17_0 and 17_1 to 17_n are selectively operated by the 8-bit signal.

  For example, when the signal supplied from the temperature sensor 19 is significantly higher than a specified value, the selection signal generator 18c, for example, as shown in FIG. 3A, based on the output signal of the transistor size determiner 18b, for example, an amplifier circuit 17_0. , 17_1 to 17_n are all selected and driven. In this case, the total size of the transistors in the inverter circuit constituting the amplifier circuits 17_0 and 17_1 to 17_n is maximized. For this reason, the negative resistance of the negative resistance circuit (proportional to the transconductance gm) is maximized, and the maximum gain can be obtained. Therefore, the oscillation circuit 11 can perform a high-speed oscillation operation.

  On the other hand, for example, when the signal supplied from the temperature sensor 19 is lower than a specified value, the selection signal generator 18c is based on the output signal of the transistor size determiner 18b, as shown in FIG. A part of 17_1 to 17_n, for example, the amplifier circuits 17_0 and 17_1 are selected and driven. In this case, the total size of the transistors in the inverter circuit constituting the amplifier circuits 17_0 and 17_1 to 17_n is smaller than the maximum value. Therefore, a high-speed oscillation operation can be performed with less power than in FIG.

  Further, when the amplitude of the signal of the oscillation circuit 11 reaches a predetermined threshold, the amplitude detector 18a supplies a high level signal, for example, to the transistor size determiner 18b. Based on this signal, the transistor size determiner 18b outputs a signal that minimizes the size of the transistors constituting the variable amplifier circuit 17. Based on this signal, the selection signal generator 18c selects and operates only the amplifier circuit 17_0, for example. For this reason, the resistance value of the variable amplifier circuit 17 is minimized, and oscillation can be maintained with low power consumption. That is, it is possible to reduce power consumption during the steady operation of the oscillation circuit 11.

  In the above description, the control unit 18 controls the amplifier circuits 17_0 and 17_1 to 17_n based on the output signal of the temperature sensor 19, but the same control is performed based on the output signal of the voltage sensor 20 and the process condition setting unit 21. Is done.

  That is, for example, when the output signal of the voltage sensor 20 is lower than a specified value, the control unit 18 selects and drives all of the amplifier circuits 17_0 and 17_1 to 17_n, as shown in FIG. When the 20 output signals are higher than the specified value, for example, a part of the amplifier circuits 17_0 and 17_1 to 17_n are selected and driven as shown in FIG.

  Further, for example, when the output signal of the process condition setting unit 21 indicates that the operation of the transistor is slower than a specified value (the threshold voltage of the transistor is high), the control unit 18, as shown in FIG. When 17_0 and 17_1 to 17_n are all selected and driven, and the output signal indicates that the operation of the transistor is faster than a specified value (the threshold voltage of the transistor is low), for example, as shown in FIG. A part of the amplifier circuits 17_0 and 17_1 to 17_n is selected and driven.

  As described above, the control unit 18 sets the transistor size to an optimum value by using at least a part of the output signals of the temperature sensor 19, the voltage sensor 20, and the process condition setting unit 21, and the output signal of the amplitude detector 18a. Based on the above, the transistor size is set to the minimum value.

  FIG. 4 shows the relationship between transistor size (channel width) W and negative resistance (start-up time).

The negative resistance _RNQ is approximated by the following equation.

R _NQ = gm / ω ² C ₁ C ₂
Here, gm is the transconductance of the amplifier circuit 17_0,17_1~17_n, ω is the angular frequency, _{C 1} is the capacitance of the capacitor 13, _{C 2} is the capacitance of capacitor 14.

In the above equation, in the case of the first embodiment, the capacitances C ₁ and C ₂ are fixed values. Therefore, by changing the size W of the transistors of the amplifier circuits 17_0 and 17_1 to 17_n and changing gm, It can be seen that the resistance _RNQ changes.

  However, in the relationship between the transistor size W and the negative resistance shown in FIG. 4, the negative resistance has a peak with respect to the change in the transistor size W. Therefore, the transistor size W has an optimum value in relation to the negative resistance.

  In the first embodiment, when the oscillation circuit 11 is started, the maximum value of the transistor size W is set so that the negative resistance is maximized, and in the steady state, it is necessary to reduce power consumption and maintain oscillation. A minimum transistor size W is set.

  FIG. 5 shows the relationship between the transistor size ratio, negative resistance, and current consumption.

  As shown in FIG. 5, at the start of oscillation, the transistor size ratio is set to, for example, about 130, the negative resistance is set to about 300Ω, and the current consumption is set to about 1.2 mA. 10. Negative resistance is set to about 50Ω and current consumption is set to about 0.2 mA. In this case, the current consumption during steady state is reduced to about 1/6 of the current consumption during startup.

  FIGS. 6A and 6B show start-up times when the circuits shown in FIGS. 1 and 2 are simulated based on the transistor size ratio (negative resistance) shown in FIG. As shown in FIG. 6A, when the size of the transistor is small and the negative resistance is about 50Ω, the start-up time is about 1.2 ms. Further, as shown in FIG. 6B, when the transistor size is large and the negative resistance is about 300Ω, the startup time is about 0.2 ms. Thus, it can be seen that the start-up time of the oscillation circuit 11 is shortened to 1/6 by increasing the negative resistance 6 times.

  FIG. 7 shows the relationship between transistor size and negative resistance, for example, using temperature as a parameter. In FIG. 7, A shows the best case where the temperature is relatively low, B shows the case where the temperature is normal, and C shows the worst case where the temperature is high.

  As shown by the characteristic A in FIG. 7, when the temperature is low, the negative resistance can be set to about 300Ω in a state where the size ratio of the transistor is smaller than the case shown by the characteristics B and C in FIG. . For this reason, it turns out that high-speed oscillation is possible with little electric power.

  Further, as shown by C in FIG. 7, when the temperature is high, the negative resistance can be set to about 300Ω in a state where the size ratio of the transistors is larger than in the cases shown by A and B in FIG. . For this reason, it can be seen that a larger amount of electric power than the characteristic indicated by A in FIG. 7 is required to start the oscillation circuit.

  According to the first embodiment, the control unit 18 uses the output signals of the temperature sensor 19, the voltage sensor 20, and the process condition setting unit 21 when starting the oscillation circuit 11, and uses the amplification circuit 17_0. , 17_1 to 17_n are selectively operated to change the total channel width. For this reason, the optimum negative resistance can be set without being affected by variations in operating environment such as temperature and power supply voltage or process conditions, and the oscillation circuit 11 can be started up at high speed.

  In addition, since the total channel width of the amplifier circuits 17_0 and 17_1 to 17_n is changed based on variations in temperature, power supply voltage, or process conditions, excessive power consumption is not required, and the oscillation circuit 11 is configured with low power consumption. Can be activated.

  Furthermore, when the signal amplitude of the oscillation circuit 11 reaches a specified value, the control unit 18 immediately changes the amplification circuits 17_0 and 17_1 to 17_n to the normal configuration. That is, the control unit 18 sets a minimum circuit configuration necessary for the oscillation circuit 11 to maintain oscillation after startup. For this reason, it is possible to reduce the power consumption in the steady state.

  In the first embodiment, the control unit 18 selectively operates the amplifier circuits 17_0 and 17_1 to 17_n based on the temperature, voltage, and process conditions, and changes the total channel width. However, the present invention is not limited to this. For example, the total channel width can be changed based on specifications such as the use of the semiconductor device on which the oscillation circuit 11 is mounted.

(Second Embodiment)
FIG. 8 and FIG. 9 show a second embodiment, in which the present embodiment is applied to a Colpitts type oscillation circuit.

  In the Colpitts oscillation circuit 30 shown in FIG. 8, a feedback resistor 32 is connected between both ends of the resonator 12. A capacitor 33 is connected between one end of the resonator 12 and the ground. A current source 35 is connected between the supply node of the power supply VDD and the resistor 32. A capacitor 36 is connected between the connection node of the current source 35 and the resistor 32 and the ground. Further, a variable amplifier circuit 37 is connected between the connection node of the current source 35 and the resistor 32 and the ground.

  The variable amplifier circuit 37 includes a plurality of amplifier circuits 37_0 and 37_1 to 37_n. Each amplifier circuit 37_0, 37_1 to 37_n is mainly composed of, for example, an nMOS transistor N3. That is, one end of the current path of the nMOS transistor N3 is connected between the current source 35 and the ground, and the gate electrode is connected to a connection node between the resistor 32 and the capacitor 33.

  The amplifier circuits 37_0 and 37_1 to 37_n are selectively driven by the control unit 18. A temperature sensor 19, a voltage sensor 20, and a process condition setting unit 21 are connected to the control unit 18. The control unit 18 selectively drives the amplifier circuits 37_0 and 37_1 to 37_n based on the output signals of the temperature sensor 19, the voltage sensor 20, and the process condition setting unit 21.

  The resistor 32, the capacitors 33 and 36, and the amplifier circuits 37_0 and 37_1 to 37_n constitute a negative resistance circuit.

  FIG. 9 shows a specific example of the amplifier circuits 37_0 and 37_1 to 37_n. Since each of the amplifier circuits 37_0 and 37_1 to 37_n has the same configuration, only the amplifier circuit 37_0 will be described.

  The amplifier circuit 37_0 is configured by a three-state amplifier. That is, the nMOS transistor N4 is connected between the constant current source 35 and the nMOS transistor N3. The gate electrode of the nMOS transistor N4 is connected to one output terminal of the control unit 18.

  In the amplifier circuits 37_0 and 37_1 to 37_n, when “n” is, for example, “7”, the control unit 18 outputs, for example, an 8-bit signal. The amplifier circuits 37_0 and 37_1 to 37_n are selectively operated by the 8-bit signal. The controller 18 selectively operates the amplifier circuits 37_0 and 37_1 to 37_n based on the output signals of the temperature sensor 19, the voltage sensor 20, and the process condition setting unit 21 at the time of activation.

  For example, when the signal supplied from the temperature sensor 19 is higher than a specified value, the control unit 18 selects and drives all the amplifier circuits 37_0 and 37_1 to 37_n, for example. In this case, the total size of the transistors N3 constituting the amplifier circuits 37_0 and 37_1 to 37_n is maximized. For this reason, the negative resistance of the negative resistance circuit (proportional to the transconductance gm) is maximized, and the maximum gain can be obtained. Therefore, the oscillation circuit 31 can perform a high-speed oscillation operation.

  On the other hand, for example, when the signal supplied from the temperature sensor 19 is lower than a specified value, the control unit 18 selects and drives, for example, some of the amplifier circuits 37_0 and 37_1 to 37_n. In this case, the total size of the transistors N3 constituting the amplifier circuits 37_0 and 37_1 to 37_n is smaller than the maximum value. For this reason, a high-speed oscillation operation is possible with a small amount of power.

  Also in the Colpitts oscillation circuit of the second embodiment, the control unit 18 changes the total size (transconductance gm) of the transistor N3 constituting the variable amplifier circuit 37 based on the temperature, voltage, and process conditions at the time of startup. As a result, high-speed oscillation is possible, and power consumption can be reduced in a steady state.

  In the second embodiment, the control unit 18 selectively operates the amplifier circuits 17_0 and 17_1 to 17_n based on the temperature, voltage, and process conditions to change the total channel width. However, the present invention is not limited to this, and the total channel width can be changed based on, for example, the specifications of the semiconductor device on which the oscillation circuit 11 is mounted, as in the first embodiment.

(Third embodiment)
In the first and second embodiments, by changing the size of the transistors of the oscillation circuits 11 and 31 on the basis of temperature, voltage, process conditions, or specifications, high-speed oscillation is possible at start-up, and low consumption during steady state. Electricity was made possible.

  On the other hand, in the third embodiment, the oscillation signal supplied to the oscillation circuit is changed based on, for example, process conditions and specifications, so that the oscillation circuit can be started at a high speed and the power consumption can be reduced.

  FIG. 10 shows an oscillation circuit 41 according to the third embodiment. An excitation circuit 43 that starts the oscillation circuit 41 is connected to the oscillation circuit 41. The oscillation circuit 41 is driven by, for example, the power supply voltage VDD, and the excitation circuit 43 is driven by, for example, the power supply voltage Vdd (<VDD) lower than the power supply voltage VDD.

  In the oscillation circuit 41, for example, a capacitor 13 is connected between one end of the resonator 12 made of, for example, a crystal resonator and the ground, and a capacitor 14 is connected between the other end and the ground. A feedback resistor 15 is connected between both ends of the resonator 12. Further, an amplifier circuit 42 is connected between both ends of the resonator 12. The amplifier circuit 42 is constituted by a CMOS inverter circuit including, for example, a pMOS transistor P1 and an nMOS transistor N1. One end of the pMOS transistor P1 is connected to a node to which the power supply voltage VDD is supplied, and the other end is grounded via the nMOS transistor N1. The gate electrodes of the pMOS transistor P1 and the nMOS transistor N1 are connected to one end of the resonator 12, and the drains of the pMOS transistor P1 and the nMOS transistor N1 are connected to the other end of the resonator 12. The capacitors 13 and 14, the resistor 15, and the amplifier circuit 42 constitute a negative resistance circuit.

  The excitation circuit 43 oscillates an excitation signal whose frequency changes for a certain period when the oscillation circuit 41 is activated, and supplies the oscillation signal to the oscillation circuit 41. This excitation signal is a signal that includes a specific oscillation frequency fc of the crystal resonator as the resonator 12, for example, and once sweeps a frequency in the range of, for example, + -10% of the oscillation frequency fc. That is, the excitation circuit 43 oscillates a signal having a lower frequency from a signal having a frequency higher than the oscillation frequency fc, or oscillates a signal having a higher frequency from a signal having a frequency lower than the oscillation frequency fc.

  Further, for example, the output signal of the process condition setting unit 21 and the output signal of the specification information setting unit 44 are supplied to the excitation circuit 43. The specification information setting unit 44 sets information (spec information) related to the specifications of the semiconductor device on which the oscillation circuit 41 is mounted. The semiconductor device is, for example, an in-vehicle semiconductor device, or a commercial semiconductor device. Spec information such as being is set. The excitation circuit 43 changes the frequency change rate of the excitation signal, that is, the frequency increase rate or the decrease rate, based on the output signal of the process condition setting unit 21 or the spec information supplied from the spec information setting unit 44. . In other words, the excitation circuit 43 changes the frequency gradient based on the process conditions and the specification information.

  The amplitude of the excitation signal output from the excitation circuit 43 is defined by the power supply voltage Vdd and is smaller than the amplitude of the oscillation signal output from the oscillation circuit 41 defined by the power supply voltage VDD. Therefore, the oscillation circuit 41 is excited by the small amplitude excitation signal output from the excitation circuit 43.

  FIG. 11 shows an example of the excitation circuit 43. In FIG. 11, a first switch circuit 43a, a second switch circuit 43b, and a variable resistance circuit 43c are connected between a node to which a power supply voltage Vdd is supplied and the ground. The first switch circuit 43a is configured by a pMOS transistor (not shown), for example, and the second switch circuit 43b is configured by an nMOS transistor (not shown), for example. The first and second switch circuits 43a and 43b are controlled by a trigger signal. Further, the variable resistance circuit 43c is configured by, for example, a plurality of diffusion resistors or polysilicon resistors.

  The first and second switch circuits 43a and 43b are not limited to pMOS transistors and nMOS transistors. For example, a pMOS transistor and an nMOS transistor are connected in parallel, and these transistors are simultaneously turned on and off. It is also possible to use a gate. In this case, the trigger signal supplied to the first switch circuit 43a is inverted by an inverter circuit (not shown).

  A variable capacitance circuit 43e is connected between the connection node Nc of the first and second switch circuits 43a and 43b and the ground. The variable capacitance circuit 43e is composed of, for example, a plurality of MOS capacitors.

  Further, a voltage controlled oscillation circuit 43f to which the power supply voltage Vdd is supplied is connected to the connection node Nc of the first and second switch circuits 43a and 43b. The voltage controlled oscillation circuit 43f outputs an excitation signal having a frequency corresponding to the voltage of the connection node Nc.

  The variable resistance circuit 43c and the variable capacitance circuit 43e constitute a so-called integration circuit, and the resistance value of the variable resistance circuit 43c and the capacitance value of the variable capacitance circuit 43e are the output signal of the process condition setting unit 21 and the specification information setting unit. 44 based on the output signal. The output signal of the process condition setting unit 21 and the output signal of the specification information setting unit 44 are supplied to the determination circuit 43g.

  The determination circuit 43g is configured by a logic circuit (not shown) that outputs a signal for setting the resistance value of the variable resistance circuit 43c and the capacitance value of the variable capacitance circuit 43e in accordance with the process conditions and the specification information. . That is, this logic circuit constitutes a so-called table that outputs the resistance value of the variable resistance circuit 43c and the capacitance value of the variable capacitance circuit 43e corresponding to each of the process condition and the specification information. The output signal of the determination circuit 43g is supplied to the selection signal generator 43h.

  The selection signal generator 43h generates, for example, an 8-bit signal for setting the resistance value of the variable resistance circuit 43c and the capacitance value of the variable capacitance circuit 43e based on the output signal of the determination circuit 43g, and the variable resistance circuit 43c, This is supplied to the variable capacitance circuit 43e. As a result, the resistance value of the variable resistance circuit 43c and the capacitance value of the variable capacitance circuit 43e are changed.

  In the above configuration, the operations of FIGS. 10 and 11 will be described. Here, it is assumed that the first switch circuit 43a is configured by a pMOS transistor, and the second switch circuit 43b is configured by an nMOS transistor.

  The resistance value of the variable resistance circuit 43c and the capacitance value of the variable capacitance circuit 43e are set in advance by the determination circuit 43g and the selection signal generator 43h based on the output signals of the process condition setting unit 21 and the specification information setting unit 44. ing.

  When the oscillation circuit 11 is activated, the trigger signal is set to, for example, a low level as shown by a solid line in FIG. Therefore, in a state where the power supply voltage Vdd is supplied, the connection node Nc to which the first switch circuit 43a is turned on, the second switch circuit 43b is turned off, and the variable capacitance circuit 43e is connected is connected to the power supply voltage Vdd. It is charged to Vdd. The voltage controlled oscillation circuit 43f outputs a signal having a frequency higher than the specific oscillation frequency fc of the oscillation circuit 41 corresponding to the voltage Vdd of the connection node Nc.

  In this state, when the trigger signal is changed from the low level to the high level, the first switch circuit 43a is turned off, the second switch circuit 43b is turned on, and the charge of the variable capacitance circuit 43e is changed to the second switch circuit 43b, And it discharges via the variable resistance circuit 43c. For this reason, the voltage of the connection node Nc gradually decreases from Vdd. Along with this, the oscillation frequency of the voltage controlled oscillation circuit 43f is also gradually lowered.

  As described above, the oscillation frequency of the voltage controlled oscillation circuit 43f includes the oscillation frequency fc of the oscillation circuit 41. For this reason, the oscillation circuit 41 is activated when the frequency of the excitation signal becomes fc. Therefore, the oscillation circuit 41 can be activated by once sweeping the output signal of the excitation circuit 43.

  It should be noted that the excitation circuit 43 is stopped after a fixed time determined by the time constant set in the integration circuit has elapsed after supplying the trigger signal. That is, the excitation circuit 43 is stopped after the output signal sweeps once.

  In the above description, the case where the oscillation frequency of the voltage-controlled oscillation circuit 43f gradually decreases has been described. However, it is not limited to this. For example, by inverting the level of the trigger signal, the oscillation frequency of the voltage controlled oscillation circuit 43f can be gradually increased.

  In this case, the trigger signal is set to a high level as shown by a broken line in FIG. In this state, the first switch circuit 43a is turned off, the second switch circuit 43b is turned on, and the charge of the variable capacitance circuit 43e is passed through the second switch circuit 43b and the variable resistance circuit 43c. Discharged. For this reason, the connection node Nc is at the ground level, and the oscillation frequency of the voltage controlled oscillation circuit 43 f is lower than the inherent oscillation frequency fc of the oscillation circuit 41.

  In this state, when the trigger signal is changed from the high level to the low level, the first switch circuit 43a is turned on, the second switch circuit 43b is turned off, and the variable capacitance circuit 43e is charged. For this reason, the voltage of the connection node Nc gradually increases. As a result, the oscillation frequency of the voltage controlled oscillation circuit 43f gradually increases.

  FIG. 12 shows an example of an excitation signal output from the excitation circuit 43. As shown in FIG. 12A, as described above, the excitation circuit 43 includes the oscillation frequency fc of the resonator 12 and sweeps the frequency in the range of, for example, + −10% of the oscillation frequency fc only once. That is, the excitation circuit 43 oscillates an excitation signal that changes from a signal having a frequency higher than the oscillation frequency fc to a lower frequency, as indicated by a solid line S1 in FIG. 12A, or a solid line S2 in FIG. As shown, an excitation signal that changes from a signal having a frequency lower than the oscillation frequency fc to a higher frequency is oscillated.

  Further, the excitation circuit 43 shows the increase or decrease of the frequency of the excitation signal, that is, the slope of the frequency of the excitation signal, based on the output signal of the process condition setting unit 21 and the output signal of the specification information setting unit 44. Control is performed as indicated by a broken line S1 or S2 in FIG.

  Specifically, for example, when the spec information indicates a vehicle-mounted semiconductor device that requires a reliable operation under a wide range of temperature conditions, the slope of the frequency of the excitation signal is increased. For this reason, the oscillation circuit 41 can oscillate reliably.

  On the other hand, for example, when the spec information indicates a commercial semiconductor device, the frequency gradient of the excitation signal is reduced. For this reason, the excitation circuit 43 outputs a signal having a frequency close to the inherent oscillation frequency fc of the oscillation circuit 41 longer than when the frequency gradient of the excitation signal is large. Therefore, the oscillation circuit 41 can perform a high-speed oscillation operation.

  Also, as shown in FIG. 12B, the amplitude of the excitation signal output from the excitation circuit 43 operated by the power supply voltage Vdd is the oscillation driven by the power supply voltage VDD as shown in FIG. It is smaller than the signal amplitude of the circuit 41. Moreover, since the excitation circuit 43 operates only when the oscillation circuit 41 is activated, the power consumption of the excitation circuit 43 is very small. Therefore, a large power saving effect can be obtained.

  According to the third embodiment, the excitation circuit 43 includes the oscillation frequency fc of the resonator 12 based on the output signals of the process condition setting unit 21 and the specification information setting unit 44, and a frequency lower than the oscillation frequency fc. A high frequency signal is generated from the above signal or a low frequency signal is oscillated from a signal higher than the oscillation frequency fc, and the frequency gradient of the excitation signal can be changed. For this reason, even when the process condition changes or when the specification information is changed, it is possible to start the oscillation circuit 41 reliably and at high speed.

  The excitation circuit 43 is driven by a power supply voltage Vdd lower than the power supply voltage VDD of the oscillation circuit 41. For this reason, the oscillation circuit 41 can be activated by a small amplitude excitation signal output from the excitation circuit 43. Therefore, it is possible to reduce the power consumption when starting up the oscillation circuit 41.

  Furthermore, since the excitation circuit 43 is stopped immediately after the oscillation circuit 41 is activated, it is possible to reduce the power consumption in the steady state.

  FIG. 13 shows a simulation result when the oscillation circuit 41 and the excitation circuit 43 shown in the third embodiment are used. In the present embodiment, the oscillation circuit 41 can be started in about 150 μs by supplying the excitation signal from the excitation circuit 43 to the oscillation circuit 41. On the other hand, when the excitation circuit 43 is not used, it takes about 700 μs to start the oscillation circuit 41. As described above, according to the third embodiment, the startup time can be remarkably shortened, so that power consumption can be reduced.

  In the third embodiment, the resistance value of the variable resistance circuit 43c and the capacitance value of the variable capacitance circuit 43e are changed based on the process conditions and the specification conditions. However, the present invention is not limited to this, and similarly to the first and second embodiments, the resistance value of the variable resistance circuit 43c and the capacitance value of the variable capacitance circuit 43e using the output signals of the temperature sensor and the voltage sensor. Can also be set.

  In addition, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  DESCRIPTION OF SYMBOLS 11, 31, 41 ... Oscillator circuit, 12 ... Resonator, 17, 37 ... Variable amplifier circuit, 18 ... Control part, 17_0-17_n, 37_0-37_n ... Amplifier circuit, 19 ... Temperature sensor, 20 ... Voltage sensor, 21 ... Process condition setting unit, 43 ... excitation circuit, 44 ... spec information setting unit

Claims (9)

A resonator,
A negative resistance circuit connected to the resonator,
The negative resistance circuit is:
A capacitor connected to the resonator;
A resistor connected to the resonator;
At least one first amplifier circuit including at least one transistor connected to the resonator and having a first size;
A second amplifying circuit connected to the resonator and including at least one transistor having a second size equal to or smaller than the first size;
A controller that operates at least the first amplifier circuit based on at least one of an operating environment and a process condition at the time of start-up, and operates only the second amplifier circuit after the start-up. Oscillator circuit. A resonator,
A negative resistance circuit connected to the resonator,
The negative resistance circuit is:
A capacitor connected to the resonator;
A resistor connected to the resonator;
A first amplifier circuit connected to the resonator and including at least one transistor having a first size;
A second amplifier circuit including at least one transistor connected to the resonator and having a second size less than or equal to the first size;
A current source connected to the first and second amplifier circuits,
A controller that operates at least the first drive circuit based on at least one of an operating environment and a process condition at the time of start-up, and operates only the second drive circuit after the start-up. Oscillator circuit.   The first amplifier circuit includes a first transistor having a first channel width, and the second amplifier circuit includes a second transistor having a second channel width that is narrower than the first channel width. The oscillation circuit according to claim 1 or 2, characterized in that:   The first amplifier circuit includes a third transistor having a first transconductance, and the second amplifier circuit includes a fourth transistor having a second transconductance smaller than the first transconductance. The oscillation circuit according to claim 1, wherein the oscillation circuit is provided.   3. The control unit according to claim 1, wherein the control unit detects an amplitude of an output signal of the oscillation circuit, and selects only the second amplification circuit when the amplitude reaches a predetermined value. 4. Oscillator circuit. A resonator,
An oscillation circuit comprising a negative resistance circuit connected to the resonator,
The negative resistance circuit is:
A capacitor connected to the resonator;
A resistor connected to the resonator;
An amplification circuit connected to the resonator, and
An excitation circuit that generates an excitation signal that includes the oscillation frequency of the resonator and changes in frequency with time based on at least one of process information and specification information at the time of start-up, and supplies the excitation signal to the oscillation circuit. An oscillation circuit characterized by:   The oscillation circuit according to claim 6, wherein the oscillation circuit is driven with a first voltage, and the excitation circuit is driven with a second voltage lower than the first voltage.   The oscillation circuit according to claim 7, wherein the excitation circuit includes an oscillation frequency of the resonator and sweeps once from a frequency lower than the oscillation frequency to a higher frequency, or from a frequency higher than the oscillation frequency to a lower frequency. .   9. The oscillation circuit according to claim 8, wherein an increase rate or a decrease rate of a frequency of a signal output from the excitation circuit is changed based on at least one of the information regarding the process condition and the specification.

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