JP2003283306A - Oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oscillator by which an oscillation frequency fluctuates a little despite of fluctuation in power source voltage. <P>SOLUTION: A voltage Vc obtained by amplifying a constant voltage Va output by a band gap constant voltage circuit 4 is used as a reference voltage of a constant current circuit 1 and a drive voltage of delay circuits D1 to DN. As a result, even when a power source voltage supplied to the oscillator fluctuates, the fluctuation in oscillation frequency can be suppressed small. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] [0001] The present invention relates to an oscillator.
It is. In particular, oscillators with ring oscillation circuits
Things. [0002] 2. Description of the Related Art Conventional oscillators having a ring oscillation circuit
One configuration example is disclosed in JP-A-6-169237.
Ring oscillators. The ringo
FIG. 3 shows the configuration of the oscillator. Fig. 3 Ring oscillator
Is a constant current circuit 1 'and a delay circuit connected in a ring shape
And a ring oscillation circuit 2 'having D1 to DN.
Output of the constant current circuit 1 'which is not affected by changes in the ambient temperature.
To control the ring oscillation circuit 2 'based on the force current
Therefore, the oscillation frequency can be kept stable against changes in ambient temperature.
ing. [0003] However, FIG.
In the ring oscillator, the power supply voltage V_DDAgainst fluctuations in
No consideration was given to doing so. Where the constant current
Assuming that there is no variation in the constant current output from the
Voltage V_DDThe relationship between the frequency and the oscillation frequency will be described. delay
Output voltage V of circuit D1₁And the output voltage V of the delay circuit D2_TwoWhen
Are shown in FIGS. 4A and 4B. Output of delay circuit D1
Voltage V₁Logic threshold V in the process of rising_DDReaches / 2
And the output voltage V of the delay circuit D2_TwoBegins to fall.
Then, the output voltage V of the delay circuit D1₁Is the logical threshold V_DD/
2, the output voltage V of the delay circuit D2_TwoDecreases
And the logical threshold V_DDThe delay circuit is one stage up to the point where
This is the delay time td. [0004] In the ring oscillator of FIG.
Power supply voltage V_DDBecomes larger, the delay times
Output voltage V of path D1₁And the output voltage V of the delay circuit D2_TwoWith
The relationship is as shown in FIG. FIG. 4A and FIG.
The graph in FIG. 4 (b) is on the same scale. [0005] A comparison between FIG. 4A and FIG.
Power supply voltage V_DDBecomes larger, the delay circuit D
1 output voltage V₁And the output voltage V of the delay circuit D2_TwoAnd amplitude
Increases and the logical threshold V_DD/ 2 increases, so the delay circuit
The delay time td per stage increases. Therefore, delay
The delay time td per circuit stage and the number of delay circuit stages N (N
Is an odd number) and the oscillation period increases,
The oscillation frequency, which is a number, decreases. That is, the ring oscillator shown in FIG.
Source voltage V_DDWith no consideration for the fluctuation of
Power supply voltage V_DDIf the oscillation frequency fluctuates,
There was a problem of fluctuation. In the above description, the output of the constant current circuit 1 '
Although it is assumed that there is no fluctuation in the constant current, the constant voltage generation circuit 10
A circuit that outputs a constant voltage based on the Zener voltage
When used, the reference voltage V_REFBut
The reference voltage V_REFConstant with the change of
The output current of the flow circuit 1 'fluctuates. Specifically, the reference
Pressure V_REFBecomes larger, the output current of the constant current circuit 1 'becomes
growing. Then, the output current of the constant current circuit 1 'fluctuates.
Then, the charging and discharging of the input terminals of the delay circuits D1 to DN
Since the time required varies, the oscillation frequency of the ring oscillator
Wave number fluctuates. Further, Japanese Patent Application Laid-Open No. 11-340797 discloses
Discloses a voltage controlled oscillator as shown in FIG.
This voltage-controlled oscillator provides the amplitude voltage of the multivibrator 7.
Bandgap as a voltage generator that outputs a voltage
Temperature dependence of oscillation frequency by using a constant voltage circuit 6
Has been lost. However, the voltage controlled oscillator of FIG.
In the same manner as in the ring oscillator circuit of FIG.
Voltage V_DDAbout the change of oscillation frequency when fluctuates
No consideration was given. SUMMARY OF THE INVENTION In view of the above problems, the present invention provides
To provide an oscillator with small oscillation frequency fluctuations
The porpose is to do. [0010] [MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
In the oscillator according to the present invention, the first band gap
A constant voltage circuit, a second band gap constant voltage circuit,
A plurality of delay circuits connected in a ring shape.
The voltage supplied to the circuit is the first bandgap constant voltage circuit.
A ring oscillation circuit that is an output voltage of the circuit, and the second band
Constant current with the output voltage of the gap constant voltage circuit as the reference voltage
And supplies a constant current to the delay circuit.
And a circuit. From the viewpoint of miniaturization and cost reduction, the first
Bandgap constant voltage circuit and second bandgap constant voltage
Circuit and the same bandgap constant voltage circuit
desirable. [0012] BRIEF DESCRIPTION OF THE DRAWINGS FIG.
This will be described with reference to FIG. FIG. 1 shows the configuration of an oscillator according to the present invention.
Shown in In FIG. 1, the same parts as those in FIG. 3 are the same.
Is assigned. An oscillator according to the present invention comprises a constant current circuit 1;
A ring oscillation circuit 2, a band gap constant voltage circuit 4,
An amplifier 5 and resistors R2 and R3 are provided. Bandi
The output terminal of the cap constant voltage circuit 4 is the non-inverting input terminal of the amplifier 5.
Connected to child. The inverting input terminal of the amplifier 5 is connected to the resistor R3.
Connected to the output terminal of the amplifier 5 through the
One end of the resistor R2 is connected to a connection node between the input terminal and the resistor R3.
Continued. The other end of the resistor R2 is grounded. Next, the configuration of the constant current circuit 1 will be described.
I do. P-channel MOSFET (Metal Oxide Semico
nductor Field Effect Transistor)
Q1 source and P-channel transistor
And the source of P-channel transistor Q5.
And the voltage V_CTo the output terminal of the amplifier 5 that outputs
Continued. The gate of the transistor Q1 and the transistor
The gate of Q2 and the gate of transistor Q5 are common
Connected. Further, the drain of the transistor Q1 is
Connected to the drain of channel transistor Q3,
The drain of transistor Q2 is an N-channel transistor Q
4 is connected to the drain. Further, the transistor Q2
Are commonly connected. The transistor Q3 has a gate and a transistor
And the gate of the transistor Q3 are connected in common.
The gate and the drain are commonly connected. Transistor Q
3 is grounded and the source of transistor Q4 is grounded.
Grounded via anti-R1. The drain of the transistor Q5 is N channel
Connected to the drain of the transistor Q6. Tran
The gate and drain of the transistor Q6 are commonly connected. Ma
The source of the transistor Q6 is grounded. According to such a configuration, the constant current circuit 1
Supplied voltage V_CIs driven with the reference voltage of the constant current circuit 1.
It also serves as voltage. Thereby, the constant current circuit 1
And the drive of the constant current circuit 1 and the delay circuits D1 to DN.
It is possible to share the dynamic voltage with the constant current circuit 1
Band-gap constant voltage that generates a constant voltage that becomes the reference voltage
And a constant voltage which is a driving voltage of the delay circuits D1 to DN.
The bandgap circuit to be generated can be shared
You. Next, the configuration of the ring oscillation circuit 2 will be described.
I will tell. The delay circuits D1, D2,..., DN (N is an odd number)
The constant current circuit is connected to the gate and transistor of transistor Q5, respectively.
It is connected to the gate of transistor Q6. Output of delay circuit D1
The power end is connected to one end of the capacitor C1 and the input end of the delay circuit D2.
Connected. The other end of the capacitor C1 is grounded. delay
The output terminal of the circuit D2 is connected to one end of the capacitor C2 and the delay of the next stage.
It is connected to the input of a circuit (not shown). Capacitor C
The other end of 2 is grounded. The output terminal of the delay circuit DN
One end of the sensor CN, the input end of the buffer circuit 3 and the delay circuit D
1 input terminal. The other end of the capacitor CN is grounded
Is done. The capacitors C1 to CN use parasitic capacitances.
It does not matter. The ring oscillation circuit 2 having such a configuration is
Output voltage V from the output terminal of the_OUTOscillation output
Output. This output V_OUTFrequency is the oscillation frequency.
You. The delay circuit provided in N stages in the ring oscillation circuit 2
The configuration of the path will be described using the delay circuit D1 as an example.
The delay circuit D1 includes a P-channel transistor Q7,
Channel type transistor Q8 and N-channel type transistor
Star Q9 and an N-channel transistor Q10.
ing. The drain of the transistor Q7 is the transistor Q
8 and the drain of transistor Q8
Connected to the drain of transistor Q9,
The source of Q9 is connected to the drain of transistor Q10.
And the source of transistor Q10 is grounded. The voltage V is applied to the source of the transistor Q7._CBut
Applied. Transistor Q7 and transistor Q2 are
A transistor mirror, and the transistor Q10 is
A current mirror circuit is formed with the transistor Q6. Soshi
The gate of the transistor Q8 and the gate of the transistor Q9.
Ports are connected in common, and the connection node is
You. Also, the drain of the transistor Q8 and the transistor
The connection node with the drain of Q9 becomes the output terminal. The output voltage of the band gap constant voltage circuit 4 is
V_aThen, the transistors Q1, Q in the constant current circuit 1
2, supplied to the source of Q5 and delay circuits D1 to DN
Voltage V_CIs represented by equation (1). Where r_TwoIs the resistor R2
Resistance value of r_ThreeIs the resistance value of the resistor R3. V_C= (1 + r_Three/ R_Two) × V_a… (1) Output voltage V of band gap constant voltage circuit 4
_aIs a high-precision constant voltage, the voltage V_CHigh precision constant current
Pressure. As a result, the drive voltage of the ring oscillation circuit 2 and the
Fluctuation of the output current of the constant current circuit 1 and the oscillation frequency
The number stabilizes. Next, a specific example of the band gap constant voltage circuit 4 will be described.
An example will be described. One of the band gap constant voltage circuit 4
FIG. 2 shows a configuration example. Power supply voltage V_DDIs applied to the terminal
Emitter of PNP type bipolar transistor T1 and PN
The emitter of the P-type bipolar transistor T2 is connected
You. Bipolar transistor T1 base and bipolar
The bases of the transistors T2 are commonly connected. Also bye
Common connection between base and collector of polar transistor T1
Continued. To the collector of the bipolar transistor T1
Connected to collector of NPN type bipolar transistor T3
Is done. The emitter of the bipolar transistor T3 is
The NPN type bipolar transistor T4 is connected via an anti-R4.
Connected to the collector and NPN type via resistor R5
Connected to the collector of the transistor T5. Bipo
Of the bipolar transistor T4 and the bipolar transistor T5
The bases are commonly connected. Also, bipolar transistors
The base-collector of the terminal T4 is commonly connected. Bipo
The emitter of the transistor T4 is grounded,
The emitter of the transistor T5 is grounded via the resistor R6.
Is done. The collector of the bipolar transistor T2
Bipolar transistor T3 base and NPN type bipolar
The collector of polar transistor T6 is connected. Ba
The base of the bipolar transistor T6 is connected to the resistor R5 and the bipolar transistor.
Connected to the connection node with the
The emitter of the polar transistor T6 is grounded. Soshi
And the output voltage V_aOutput terminals are a resistor R4 and a resistor R5.
Connected to the connection node. The base-d of the bipolar transistor T4
Voltage V between transmitters_BE4Of the bipolar transistor T5
Source-emitter voltage V_BE5Are the expressions (2),
It can be expressed as in equation (3). In addition, Bipo
Base transistor-emitter voltage V_BE4When
Base-emitter voltage of bipolar transistor T5
V_{B E5}And the relationship of equation (4) holds. And
From equations (2) to (4), equation (5) holds. However
And the current flowing through the resistor R4 is I₁And the current flowing through the resistor R5.
Flow I_Two, Collector saturation of bipolar transistor T4
Current I_s, The resistance value of the resistor R6₆, Bipolar tran
Bipolar transistor with respect to emitter area of transistor T4
The emitter area ratio of the star T5 is N, and the thermal voltage (Boltzmann constant)
The product of the number and the absolute temperature divided by the amount of electron charge) is V_T
And (Equation 1) The output voltage V_aAre the expressions (6) and (7)
Can be expressed as Where bipolar tran
Base-emitter voltage V of transistor T4_BE4And bipo
The base-emitter voltage V of the transistor T6_BE6But
Assuming that they are equal, equation (8) is obtained from equations (6) and (7).
Stand up. Here, the resistance value of the resistor R4 is r_FourOf the resistor R5
The resistance value is r_FiveAnd Note that the emitter of the transistor T6 is
Current is I₁+ I_TwoIs a bipolar transistor
Bipolar transistor T for emitter area of T4
6 is (1 + r_Four/ R_Five)
V_BE4= V_BE6Can be realized. (Equation 2) From the equations (6) to (8), the output voltage V_aIs
It is expressed as in equation (9). [Equation 3] Here, V, which is the first term on the right side of equation (9),
_BE4Has a negative temperature coefficient.
The term has a positive temperature coefficient. Therefore, the right side of equation (9)
The resistance ratio r in the second term_Five/ R₆, Resistance ratio r_Five/ R_FourAnd Emi
The output voltage V can be set by appropriately setting the_aWarmth
Degree coefficient can be canceled. This causes a temperature change.
Output voltage V_aCan be kept constant. Ma
Power supply voltage V_DDOutput voltage V_aKeep
Can be Therefore, the band gap constant voltage circuit
Output voltage V of path 4_aIs high-precision constant voltage and
Become. Incidentally, the oscillator according to the present invention has the following reason.
Charge pump circuit such as flash memory
It is good to use it as an oscillator provided in. That is, the light source provided in the charge pump circuit
When the oscillation frequency of the oscillator changes, the charge pump circuit
The output voltage fluctuates, causing the following problem. Ma
Output voltage of the charge pump circuit
If the flash memory exceeds the withstand voltage,
It may be damaged. Next, the output of the charge pump circuit
If the input voltage is lower than the specified value,
Errors will occur. By using the oscillator according to the present invention,
The frequency changes less and the output of the charge pump circuit
Voltage fluctuation can be reduced. This allows
The problems described above are less likely to occur. [0034] According to the present invention, the oscillator is arranged in the first band.
Gap constant voltage circuit and second band gap constant voltage circuit
And a plurality of delay circuits connected in a ring shape,
The voltage supplied to the delay circuit is equal to the first band gap constant.
A ring oscillation circuit which is an output voltage of a voltage circuit;
Using the output voltage of the band gap constant voltage circuit as the reference voltage
Generating a constant current and supplying the constant current to the delay circuit
Power supply supplied to the oscillator
Constant current output from the constant current circuit even if the voltage fluctuates
And the voltage supplied to the delay circuit does not change. this
Oscillation even if the power supply voltage supplied to the oscillator fluctuates
Frequency fluctuation can be reduced. In addition, the fluctuation of the ambient temperature causes the fluctuation of the power supply voltage.
Therefore, the oscillator according to the present invention operates at ambient temperature.
Fluctuation of oscillation frequency should be reduced even if
Can be.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a configuration of an oscillator according to the present invention. FIG. 2 is a diagram illustrating a configuration of a bandgap constant voltage circuit included in the oscillator of FIG. 1; FIG. 3 is a diagram illustrating a configuration of a conventional oscillator including a ring oscillation circuit. FIG. 4 is a diagram showing an output voltage waveform of a delay circuit included in the oscillator of FIG. 3; FIG. 5 is a diagram showing a configuration of a conventional oscillator including a multivibrator. [Description of Signs] 1 constant current circuit 2 ring oscillation circuit 4 band gap constant voltage circuits D1, D2, DN delay circuit

Continuation of front page    (72) Inventor Kazuo Sato             21 Ryosan-cho, Saiin-mizozaki-cho, Ukyo-ku, Kyoto-shi             In the formula company F-term (reference) 5H420 NA12 NA15 NA23 NB02 NB12                       NB22 NB24 NC12                 5J043 AA02 AA26 LL01

Claims (1)

Claims: 1. A bandgap constant voltage circuit for outputting first and second constant voltages, and a plurality of delay circuits connected in a ring, and supplied to the delay circuits. A ring oscillation circuit whose voltage is the first constant voltage; and a constant current circuit that generates a constant current using the second constant voltage as a reference voltage and supplies the constant current to the delay circuit. Characteristic oscillator.