JP4666181B2 - OSCILLATOR CIRCUIT, ELECTRONIC CIRCUIT, SEMICONDUCTOR DEVICE HAVING THEM, WATCH AND ELECTRONIC DEVICE - Google Patents

Description

  The present invention relates to an oscillation circuit, an electronic circuit, a semiconductor device including these, a timepiece, and an electronic device.

  The oscillation circuit used in portable wristwatches and electronic devices has its main circuit part configured on a semiconductor substrate connected to a crystal resonator provided at a different location from the semiconductor substrate via an input / output terminal. It is often done. For this reason, an electrostatic protection circuit is provided on the input / output terminal side of the main circuit portion in order to protect the main circuit portion from a surge voltage entering from the outside through the input / output terminal.

However, in the conventional circuit, since the oscillation circuit driving power source is used for bypassing the surge voltage of the electrostatic protection circuit, if a fluctuation occurs in the power supply voltage of the oscillation circuit for some reason, this is caused by the parasitic circuit of the electrostatic protection circuit. There is a problem that the capacitance value fluctuates, and as a result, the oscillation frequency of the oscillation circuit fluctuates.
JP-A-8-8651

  An object of the present invention is to protect the main circuit portion from a surge voltage entering from the outside through an input / output terminal, and to oscillate at a stable frequency without being affected by fluctuations in the power supply voltage of the oscillation circuit. It is an object to provide an oscillation circuit, an electronic circuit, a semiconductor device including these, a timepiece, and an electronic device.

(1) In order to achieve the above object, the oscillation circuit of the present invention includes:
A first static voltage connected between the signal path of the oscillation circuit and the constant voltage side and bypassing the first polarity static voltage entering the signal path to the bypass constant voltage side via the first semiconductor rectifier element. An electrical protection circuit;
A second electrostatic protection circuit that is connected between the signal path and the reference potential side and bypasses the second polarity static voltage entering the signal path to the reference potential side via a second semiconductor rectifier element. When,
Including
The bypass constant voltage is a constant voltage supplied separately from the power supply voltage of the oscillation circuit.

Further, the oscillation circuit of the present invention is
A first static voltage connected between the signal path of the oscillation circuit and the constant voltage side, and bypassing the first polarity static voltage entering the signal path to the bypass constant voltage side via the first semiconductor rectifier element. An electrical protection circuit;
A second electrostatic protection circuit that is connected between the signal path and the reference potential side and bypasses the second polarity static voltage entering the signal path to the reference potential side via a second semiconductor rectifier element. When,
Including
One of the supply constant voltage from the constant voltage supply circuit and the constant voltage obtained by dividing and boosting the supply constant voltage is used as the power supply voltage of the oscillation circuit, and the other is used as the bypass constant voltage. To do.

  In electronic circuits, various constant voltages are often prepared in addition to the power supply of the oscillation circuit. In addition, the power supply voltage for the oscillation circuit and other constant voltages that are not easily affected by the voltage fluctuation are supplied from the same power supply. A voltage can also be generated.

  The oscillation circuit of the present invention employs a configuration in which the electrostatic protection circuit is connected not to the power supply side for the oscillation circuit but to the constant voltage side that is less affected by fluctuations in the power supply voltage. As a result, even if the voltage of the oscillation circuit power supply fluctuates, the constant voltage for bypass connected to the electrostatic protection circuit does not fluctuate. Therefore, the parasitic capacitance value of the semiconductor rectifying element constituting the electrostatic protection circuit The fluctuation can be effectively suppressed.

  Thus, according to the present invention, it is possible to obtain an oscillation circuit in which the oscillation frequency does not vary even when the power supply voltage of the oscillation circuit varies.

  Here, as the first and second semiconductor rectifier elements used in the electrostatic protection circuit, for example, a diode, a bipolar transistor, or the like can be used as necessary.

(2) In the present invention,
The first electrostatic protection circuit includes:
A third semiconductor rectifier element connected between the signal path of the oscillation circuit and the main power supply and bypassing the static voltage of the first polarity entering the signal path to the main power supply voltage side is formed. Also good.

The parasitic capacitance value of the third semiconductor rectifier element is
A value smaller than the parasitic capacitance value of the first semiconductor rectifier element may be set.

  In particular, the parasitic capacitance value of the third semiconductor rectifier element may be set to a value that is negligible compared to the parasitic capacitance value of the first semiconductor rectifier element.

  In this way, even when the parasitic capacitance value of the third semiconductor rectifying element changes due to fluctuations in the main power supply voltage, an oscillation output with a more stable oscillation frequency can be obtained without being substantially affected by this. Is possible.

In the present invention, the parasitic capacitance of each semiconductor rectifier element is
A part or all of the phase compensation capacitor may be used.

  By doing so, part or all of the phase compensation capacitor can be omitted, and as a result, the integration degree of the entire circuit can be further increased.

(3) Further, the oscillation circuit of the present invention includes:
A first static voltage connected between the signal path of the oscillation circuit and the constant voltage side and bypassing the first polarity static voltage entering the signal path to the bypass constant voltage side via the first semiconductor rectifier element. An electrical protection circuit;
A second electrostatic protection circuit that is connected between the signal path and the reference potential side and bypasses the second polarity static voltage entering the signal path to the reference potential side via a second semiconductor rectifier element. When,
Including
The constant voltage for bypass is
Even when a leak current occurs between the signal path and the power supply voltage line, the first and second semiconductor rectifier elements are set to values that do not turn on due to voltage fluctuations in the signal path due to the leak current. It is characterized by.

put it here,
When the power supply voltage is V _ss , the forward ON voltage of the semiconductor rectifier element is V _Fon , and the potential difference between the signal path and the power supply voltage line when a leakage current occurs is V _R ,
The bypass constant voltage V _{re g} is in the range of the power supply voltage │V _ss │ operating predetermined voltage, the following equation
│V _reg │> │V _ss │−V _R −V _Fon
You may set to the value which satisfies.

The constant voltage for bypass is
A constant voltage V _reg1 supplied separately from the constant voltage V _reg2 supplied as the power supply voltage of the oscillation circuit may be used.

The bypass constant voltage V _reg1 and the constant voltage V _reg2 supplied as the power supply voltage of the oscillation circuit are:
│V _reg1 │> │V _reg2 │
You may set so that the conditions of this may be satisfied.

Also used as a supply constant voltage and the power supply voltage of one V _reg2 oscillation circuit of the supply constant voltage a partial pressure-boosted obtained constant voltage from the constant voltage supply circuit, using the other V _reg1 as the bypass constant voltage May be.

As the bypass constant voltage,
You may use the constant voltage of a temperature characteristic with a small voltage fluctuation with respect to a temperature change. For example, since the constant voltage for driving the temperature sensor has a small temperature characteristic, it can be used as a constant voltage for bypass.

  A static voltage having a first polarity that enters the signal path between the output of the constant voltage supply circuit that supplies the constant voltage for bypass and the reference potential is bypassed via the first semiconductor rectifier element. A discharging semiconductor rectifier element for discharging to the constant voltage side may be provided.

  (4) An electronic circuit may be formed using the oscillation circuit of the present invention.

  The electronic circuit may include an oscillation circuit and a drive circuit that drives a driven portion based on an output of the oscillation circuit.

  This makes it possible to obtain an electronic circuit that can operate satisfactorily using a stable frequency output supplied from the oscillation circuit.

  Further, a semiconductor device may be formed using the oscillation circuit or the electronic circuit of the present invention.

  That is, when an oscillation circuit using a crystal resonator or an electronic circuit using the oscillation circuit is formed on a semiconductor device, the main circuit portion of the oscillation circuit formed on a predetermined circuit board and the circuit board In many cases, crystal resonators provided in different areas are connected via wiring. In this case, a static voltage such as a surge voltage may enter the main circuit portion as noise from a connection portion between the crystal resonator and the main circuit portion, and the inside of the circuit may be destroyed.

  Even in such a case, according to the present invention, it is possible to satisfactorily remove static voltage such as a surge voltage entering the circuit by using the electrostatic protection circuit, and each part of the circuit using the stable oscillation output. A semiconductor device that can be operated satisfactorily can be realized.

  A timepiece may be formed using the oscillation circuit or the electronic circuit of the present invention. The timepiece may include an oscillation circuit and a time display unit that displays a time based on the oscillation circuit.

  According to the present invention, even when the power supply voltage of the main power supply fluctuates, it is possible to obtain a timepiece capable of performing an accurate time measuring operation without being affected by the fluctuation.

  Further, an electronic device may be formed using the oscillation circuit or the electronic circuit of the present invention.

  Further, the electronic device may be formed to include an oscillation circuit, a drive circuit that drives a driven unit using the output of the oscillation circuit, and a driven unit.

  As a result, even when the power supply voltage of the oscillation circuit fluctuates, it is possible to realize an electronic device that can generate an accurate oscillation output without being affected by the fluctuation and operate each part of the circuit.

  In particular, a timepiece and an electronic device formed using the oscillation circuit or the electronic circuit of the present invention are extremely suitable as a portable timepiece using a replaceable battery or a rechargeable secondary battery as a main power source or an electronic device. It will be something.

  A preferred embodiment of the present invention will be described in detail by taking the case where the present invention is applied to an analog display type wristwatch as an example.

(1) Overall Configuration FIG. 1 shows an example of an electronic circuit used in this wristwatch.

  This wristwatch incorporates a power generation mechanism (not shown). When the user wears a wristwatch and moves his arm, the rotating weight of the power generation mechanism rotates, and the power generation rotor is rotated at high speed by the kinetic energy at that time, and an AC voltage is output from the power generation coil 10 provided on the power generation stator side. The

  This AC voltage is rectified by the diode 12 to charge the secondary battery 14. The secondary battery 14 constitutes a main power supply 20 together with the booster circuit 16 and the auxiliary capacitor 18.

In this embodiment, when the voltage of the secondary battery 14 is low and less than the driving voltage of the timepiece, the voltage of the secondary battery 14 is converted to a high voltage that can be driven by the booster circuit 16 and stored in the auxiliary capacitor 18. . Then, the clock circuit 30 operates with the voltage of the auxiliary capacitor 18 as the power supply voltage V _ss .

The clock circuit 30 is configured as a semiconductor device, generate an oscillation output of the frequency of the oscillation frequency set in advance by using a crystal oscillator 42 connected through the terminal to the semiconductor device, wherein 32768H _Z By dividing the oscillation output, drive pulses having different polarities are output every second. This drive pulse is input to the drive coil 22 of the step motor connected to the timepiece circuit 30. As a result, a step motor (not shown) rotates the rotor every time a drive pulse is energized, drives a second hand, a minute hand, and an hour hand (not shown), and displays the time in an analog manner.

(2) Crystal Oscillation Circuit FIG. 2 shows a specific circuit configuration of the crystal oscillation circuit 40 that is a feature of the present embodiment.

The crystal oscillation circuit 40 basically includes an inverter 60, a feedback resistor 62, a drain resistor 64, and phase compensation capacitors 66 and 68, and divides the oscillation output of the oscillation frequency f _s into a frequency and functional circuit. Output to 81.

The first and second constant voltage generation circuits 32-1 and 32-2 generate first and second constant voltages V _reg1 and V _reg2 from the voltage V _ss supplied from the main power supply 20. These first and second constant voltages V _reg1 and V _reg2 may be the same voltage or different voltages. The second voltage V _reg2 is used as an oscillation circuit driving power supply voltage and applied to the inverter 60.

  Incidentally, the timepiece circuit 30 shown in FIG. 1 is basically formed as a CMOS-IC 300 as a semiconductor device except for the crystal resonator 42 as shown in FIG. The IC 300 and the crystal unit 42 are connected via a wiring 310.

  That is, the crystal oscillator 42 is connected to the main circuit portion of the crystal oscillation circuit 40 configured inside the CMOS-IC 300 via the input / output terminals. Therefore, a surge voltage may be input from this input / output terminal to destroy the internal circuit.

  As such a surge voltage, for example, a surge voltage entering from a jig at the time of product assembly, a surge voltage entering from an operator such as a human, and the like are conceivable.

  For this reason, electrostatic protection circuits 200-1 and 200-2 are provided inside the crystal oscillation circuit 40.

  Each of the electrostatic protection circuits 200-1 and 200-2 is provided for each signal path connected to each input terminal. Since each of the electrostatic protection circuits 200-1 and 200-2 has the same configuration, one electrostatic protection circuit 200-1 will be described as an example here.

  This electrostatic protection circuit 200-1 selectively bypasses the resistor 70 and the negative polarity static voltage entering the signal path of the oscillation circuit via the first semiconductor rectifier element 72 to the bypass constant voltage side. 1 electrostatic protection circuit unit 210 and a second electrostatic protection circuit unit that selectively bypasses a positive-polarity static voltage entering the signal path of the oscillation circuit to the ground side via the second semiconductor rectifier element 74 220.

  The resistor 70 is connected in series to the signal path, and protects the rectifier elements 72 and 74 from surge voltage.

The first and second semiconductor rectifier elements 72 and 74 are configured using PN junction type diodes. The diode constituting the first semiconductor rectifying element 72 is reversely connected to the constant voltage (V _reg1 ) output terminal side of the constant voltage generating circuit 32-1 and constitutes the second semiconductor rectifying element 74. The diode is forward-connected to the ground (V _DD ) side.

As a result, the negative polarity surge voltage entering from the outside is bypassed to the constant voltage terminal V _reg1 side, and the positive polarity surge voltage is bypassed to the ground side, preventing entry into the semiconductor circuit. .

A feature of the present embodiment is that the constant voltage V _reg1 that does not change even when the power supply voltage V _reg2 of the driving power source of the oscillation circuit fluctuates is used as the constant voltage for bypass of the first semiconductor rectifier element 72. It is in.

2 to 4 show various embodiments for supplying such a constant voltage V _reg1 .

  First, the electronic circuit shown in FIG. 2 will be described.

The electronic circuit of the present embodiment includes a plurality of constant voltage generation circuits 32-1 and _32-2 that generate different constant voltages V _reg1 and V _reg2 , and drives the temperature sensor 400 with one constant voltage V _reg1. The crystal oscillation circuit 40 is driven by the other constant voltage V _reg2 .

  The temperature sensor 400 detects the temperature of the usage environment of the electronic circuit, and supplies the detection signal to the frequency divider and function circuit 81.

  Here, the frequency-dividing circuit and functional circuit 81 functions as a frequency-dividing circuit that divides the output of the crystal oscillation circuit 40 and also functions as various functional circuits.

A feature of the crystal oscillation circuit 40 of the present embodiment is that a constant voltage for bypass to which the first electrostatic protection circuit 210 is connected is a constant voltage different from the constant voltage for driving the oscillation circuit, specifically a temperature sensitive. This is because the constant voltage V _reg1 for driving the sensor 400 is used.

Specifically, in each of the first electrostatic protection circuits 200-1 and 200-2, the pn junction diodes 72 and 72 functioning as the first semiconductor rectifier elements are connected at one end side to the signal path side of the oscillation circuit. The other end is connected to the constant voltage V _reg1 side.

  Next, the embodiment shown in FIG. 3 will be described.

In this embodiment, a constant voltage generation circuit 32-2 that generates a constant voltage V _reg2 for driving the crystal oscillation circuit 40 and a bypass constant voltage V _reg1 dedicated to the electrostatic protection circuits 200-1 and 200-2 are generated. And a constant voltage generating circuit 32-1.

The crystal oscillation circuit 40 is driven by the constant voltage V _reg2 .

In each of the electrostatic protection circuits 200-1 and 200-2, one end side of the diodes 72 and 72 functioning as the first semiconductor rectifier element is connected to the constant voltage V _reg1 side dedicated to the electrostatic protection circuit.

  Next, the embodiment shown in FIG. 4 will be described.

The electronic circuit of the present embodiment includes a constant voltage generation circuit 32 for generating a predetermined constant voltage V _reg1, and a voltage dividing circuit 33 that generates the constant voltage V _reg1 by dividing a predetermined constant voltage V _reg2.

The crystal oscillation circuit 40 is driven using the constant voltage V _reg2 .

Furthermore, each of the electrostatic protection circuits 200-1 and 200-2 is connected to the constant voltage V _reg1 side via diodes 72 and 72 that function as first semiconductor rectifier elements.

If necessary, the crystal oscillation circuit 40 is driven using the constant voltage V _reg1 and the electrostatic protection circuits 200-1 and 200-2 are connected to the constant voltage V _reg2 side. In addition, when a plurality of constant voltages are divided and output from the voltage dividing circuit 33, either the plurality of divided voltages or the constant voltage _Vreg1 is used for driving the crystal oscillation circuit 40. It is also possible to adopt a configuration in which any one of the remaining devices is connected to the electrostatic protection circuits 200-1 and 200-2. Further, a booster circuit may be used instead of the voltage divider circuit.

By adopting the configuration shown in FIGS. 2 to 4, even if the power supply voltage V _ss of the main power supply 20 and the power supply voltage V _{reg2 of the} oscillation circuit fluctuate due to some cause, the parasitic of each of the semiconductor rectifier elements 72 and 74 can The capacitance does not change, and the oscillation frequency f _s of the crystal oscillation circuit 40 is always a constant value.

  The details will be described below.

FIG. 5 shows the relationship between the bypass constant voltage V _reg1 and the power supply voltage V _ss . The absolute value of the power supply voltage V _ss (which takes a negative value in this embodiment) supplied from the main power supply is always a constant voltage V _reg1 (a negative value in this embodiment) output from the constant voltage generation circuit 32. Have a value greater than the absolute value. However, the power supply voltage V _ss often fluctuates as shown in FIG. 5 due to load fluctuations, the state of charge of the main power supply 20, and the like.

On the other hand, the constant voltage V _reg1 output from the constant voltage generating circuit 32 is less affected by the voltage V _ss of the main power supply and is already a constant voltage.

Hereinafter, a problem that occurs when the first semiconductor rectifying element 72 is connected to the voltage V _ss side of the main power supply 20 having a large capacity as in the prior art will be described.

When the voltage V _ss of the main power supply 20 varies, the values of the parasitic capacitances of the first and second semiconductor rectifying elements 72 and 74 made of semiconductors vary.

  The parasitic capacitance C of the semiconductor rectifier elements 72 and 74 made of PN junctions inside the IC, particularly the P and N junctions of the diode is usually expressed by the following equation.

同式から、電源電圧Ｖ_A＝Ｖ_ssが変化すると、この寄生容量Ｃが変化することが理解される。

From this equation, it is understood that the parasitic capacitance C changes when the power supply voltage V _A = V _ss changes.

When the parasitic capacitance C changes, as a result, the oscillation frequency f _s of the oscillation circuit 40 also varies. This will be described in more detail below.

(2-1) Oscillation Frequency Variation Countermeasure FIG. 6A shows an equivalent circuit of the oscillation circuit 40.

  FIG. 6B shows a crystal resonator 42 and FIG. 6C shows an equivalent circuit thereof.

  When the equivalent circuit shown in FIG. 6C is used, the oscillation circuit 40 shown in FIG. 6A is expressed as a circuit shown in FIG.

The oscillation frequency f _s of the LC oscillation circuit (oscillation circuit 40) represented by the equivalent circuit of FIG. 6D is represented by the following equation.

この式から、発振回路の内部容量Ｃ_G'が変わると、発振周波数ｆ_sが変動することがわかる。すなわち、前記数２には、第１、第２の半導体整流素子７２、７４の寄生容量値Ｃ_VDD、Ｃ_VSSが含まれるため、これらの値が変化すると、発振周波数ｆ_sが変動してしまう。

From this equation, it can be seen that the oscillation frequency f _s varies as the internal capacitance C _{G ′} of the oscillation circuit changes. That is, since the equation 2 includes the parasitic capacitance values C _VDD and C _{VSS of} the first and second semiconductor rectifying elements 72 and 74, the oscillation frequency f _s changes when these values change. .

On the other hand, in the present embodiment, the first semiconductor rectifying element 72 is connected to a constant voltage V _reg1 where the voltage does not vary. For this reason, the crystal oscillation circuit 40 can always generate an oscillation output having a constant frequency f _s without being affected by fluctuations in the power supply voltage V _ss .

  Furthermore, by adopting such a configuration, the values of the parasitic capacitances of the first and second semiconductor rectifier elements 72 and 74 are always constant. Therefore, the parasitic capacitance value can be positively utilized as the phase compensation capacitors 66 and 68. Thereby, the capacitance values of the phase compensation capacitors 66 and 88 shown in FIGS. 2 to 4 can be made small, or in some cases, these capacitors 66 and 88 can be omitted.

  By doing so, it is possible to reduce the number of components of the crystal oscillation circuit 40 and increase the degree of integration.

  In addition, according to the present embodiment, the parasitic capacitance of the first and second semiconductor rectifier elements 72 and 74 is utilized as part or all of the phase compensation capacitors 66 and 68, whereby the semiconductor rectifier element 72 is used. 74 itself can have a large parasitic capacitance value.

  That is, when the phase compensation capacitors 66 and 68 and the diodes 72 and 74 are provided completely separately, the diodes 72 and 74 are reduced from the viewpoint of reducing the capacity of the entire crystal oscillation circuit 40 and reducing its power consumption. Must have a small parasitic capacitance. In this case, the electrostatic breakdown resistance also decreases according to the parasitic capacitance value.

  On the other hand, in the present embodiment, a semiconductor element having a large parasitic capacitance value can be used by actively utilizing the parasitic capacitance of the semiconductor rectifying elements 72 and 74 as the phase compensation capacitor. As a result, the electrostatic breakdown resistance of the elements 72 and 74 themselves can be increased, and the electrostatic protection capability of the entire circuit can be increased.

(3) Other Embodiments FIG. 7 shows another example of the present invention. The electrostatic protection circuit of this embodiment is characterized in that the third semiconductor rectifier element 78 is used and is connected in the reverse direction to the main power supply V _ss . As a result, a surge voltage bypass circuit can be formed on the side of the main power supply 20 having a large capacity, so that the electrostatic breakdown resistance of the electrostatic protection circuit 200 can be further increased.

In this case, the parasitic capacitance value of the third semiconductor rectifying element 78 varies under the influence of the variation of the power supply voltage V _ss . For this reason, by setting the parasitic capacitance value of the first semiconductor rectifier element 72 to be about one to two digits larger than the parasitic capacitance value of the third semiconductor rectifier element 78, the parasitic capacitance value of the third semiconductor rectifier element 78 is increased. It is desirable that the fluctuation amount of the capacitance value be within the influence of about several percent with respect to the fluctuation amount of the combined parasitic capacitance value of the first semiconductor rectifier element 72 and the third semiconductor rectifier element 78. As a result, the capacitance value of the entire circuit is always stabilized, and a more stable oscillation output can be obtained.

(4) Comparison with Prior Art FIG. 8 shows an example of a conventional electrostatic protection circuit in which the semiconductor rectifier element 72 is connected to the main power supply V _ss side. In the conventional example shown in FIG. 8, the first semiconductor rectifying element 72 connected to the main power supply whose power supply voltage V _ss varies is expressed as a circuit as an element whose parasitic capacitance value C _VSS varies.

  Here, regarding an example of the crystal oscillation circuit using the conventional electrostatic protection circuit, the frequency deviation was examined as described below.

In the conventional circuit of FIG. 8, C _G , which is a combined capacitance of an internal circuit of an IC (semiconductor device) including the electrostatic protection circuit 200 as viewed from the gate terminal and the drain terminal of the transistor constituting the gate 60 of the oscillation circuit 40. measured data of C _D became a value shown by the following equation. Here, since the resistance value R _f of the resistor 62 is extremely large, from the value of C _G shown in the following equation the value of C _DO is omitted, the value of C _GO from the value of C _D is omitted.

この従来回路において、電源電圧Ｖ_ssが１．１ボルトから２．４ボルトへ変動したとき、第１の半導体整流素子７２の寄生容量値Ｃ_VSSの変動量はΔＣ_VSS＝０．０７（ＰＦ）であった。

In this conventional circuit, when the power supply voltage V _ss varies from 1.1 volts to 2.4 volts, the variation amount of the parasitic capacitance value C _VSS of the first semiconductor rectifying element 72 is ΔC _VSS = 0.07 (PF). Met.

  Next, the ratio of the fluctuation amount of the parasitic capacitance value to the entire capacitance of the crystal oscillation circuit 40 is examined.

First, when determining the ratio of the variation of the parasitic capacitance value of the electrostatic protection circuit 200-2 for C _G shown in Equation 3, the values are as shown in the following equation.

また、数３に示すＣ_Dに対する静電保護回路２００−１の寄生容量値の変動量の比を求めると、その値は次式で示すようになる。

Further, when determining the ratio of the variation of the parasitic capacitance value of the electrostatic protection circuit 200-1 against C _D shown in Expression 3, the value is as shown by the following equation.

ここで、Ｃ_GP、Ｃ_DPは、発振回路４０の配線容量値をそれぞれ表すものである。

Here, C _GP and C _DP represent wiring capacitance values of the oscillation circuit 40, respectively.

  When the value of the frequency deviation of the oscillation circuit is obtained from the fluctuation amount of the parasitic capacitance value, the value is (df / dv) = 3 (PPM). When this is converted into a monthly difference, it takes about 8 seconds. For example, when the monthly difference allowed for the clock is about 15 seconds, it is not at all acceptable that 8 seconds of the 15 seconds are caused by the fluctuation of the parasitic capacitance value.

On the other hand, as shown in FIGS. 2 to 4, by connecting the first semiconductor rectifier element 72 to the power supply V _reg1 where the voltage does not vary, such a variation in the parasitic capacitance value can be almost ignored. The frequency deviation of the oscillation frequency of the crystal oscillation circuit 40 itself can be improved to a negligible level as compared with the conventional circuit.

Similar verification was performed on the crystal oscillation circuit 40 using the electrostatic protection circuit of another embodiment shown in FIG. FIG. 9 is an equivalent circuit diagram of the electrostatic protection circuit. In this case, the third semiconductor rectifying element 78 is an element whose parasitic capacitance value C _VSS changes.

Also in the circuit shown in FIG. 9, the parasitic capacitance value of the third semiconductor rectifying element 78 is formed to be sufficiently smaller than the parasitic capacitance value of the first semiconductor rectifying element 72, so that the parasitic capacitance value C _VSS varies. Even in this case, the frequency deviation of the entire circuit can be greatly reduced as compared with the case where the electrostatic protection circuit shown in FIG. 8 is used.

(5) Embodiment of constant voltage V _reg1 for bypass connected to electrostatic protection circuit 5-1: First embodiment The constant voltage V _reg1 for bypass connected to electrostatic protection circuit 200-1 is an oscillation circuit. Even when a leak current is generated between the 40 signal paths and the line of the power supply voltage V _ss , the first and second semiconductor rectifier elements 72 and 74 are caused by voltage fluctuations in the signal path caused by the leak current. Set to a value that does not turn on.

For example, as shown in FIG. 12, the power supply voltage is V _ss , the forward ON voltage of the semiconductor rectifier elements 72 and 74 is V _Fon , and the leakage current is generated between the signal path and the power supply voltage line. When the potential difference is V _R , the constant voltage for bypass | V _reg | is within the range of the operation scheduled voltage of the power supply voltage | V _ss | (for example, within a range of 1.2 to 2 V), and the following expression | V _reg | > │V _ss │-V _R -V _Fon
Set to a value that satisfies.

As a result, even when a leakage current is generated between the signal path of the oscillation circuit 40 and the power supply voltage V _ss line, stable oscillation can be maintained without being affected by this. Details will be described below.

In the embodiment, the constant voltage generating circuits 32-1 and 32-2 are separately formed, the bypass constant voltage V _reg1 connected to the electrostatic protection circuits 200-1 and 200-2, and the oscillation circuit 40. The case where the constant voltage V _reg2 supplied to is separately formed has been described as an example. Here, in order to simplify the description, both constant voltage generation circuits 32 are formed as the same circuit, and the same constant voltage V _reg is provided to the electrostatic protection circuits 200-1 and 200-2 and the oscillation circuit 40. A case will be described.

In the circuit of the present embodiment, the bypass constant voltage V _reg1 connected to the electrostatic protection circuits 200-1 and 200-2 is connected to the input / output terminals 71-1 and 71-2 of the oscillation circuit 40 and the power supply voltage V _ss. Even when a leak current occurs between the lines 73 due to environmental changes such as humidity, it is preferable to set the oscillation circuit 40 so that the oscillation operation does not stop.

That is, there is an environmental change such as humidity between the input / output terminals 71-1 and 71-2 of the oscillation circuit 40 to which the electrostatic protection circuits 200-1 and 200-2 are added and the power supply voltage V _ss line 73. Depending on the case, a leakage current may occur.

As shown in FIG. 11, when the IC is mounted on the circuit board, this leakage current is generated due to a decrease in the insulation resistance of the circuit board due to environmental changes such as humidity. Specifically, in the circuit board shown in FIG. 11, the insulation resistance between the wiring pattern 310 of the circuit board connected to the input / output terminal of the oscillation circuit and the wiring pattern (power supply voltage line) of the power supply voltage V _ss It is generated by lowering. In particular, this phenomenon occurs remarkably when the material of the circuit board is polyimide.

FIG. 12 shows an equivalent circuit when a leak current is generated between the input / output terminals 71-1 and 71-2 of the oscillation circuit 40 and the line 73 of the power supply voltage V _ss .

When the leakage current is generated, the semiconductor rectifying device forms an electrostatic protection circuit 200-1 and 200-2 D2 (72), the forward voltage V _F indicated by the following equation is applied (electrostatic protection circuit The voltage drop due to the resistance r of 200-1 and 200-2 is so small that it is ignored).

V _F = │V _ss │-V _R -│V _reg │ ・ ・ ・ (Equation 6)
At this time, a forward on-voltage at which the semiconductor rectifier elements 72 and 74 are turned on is _{defined as VFon} . This forward on-voltage is usually about 0.6V. Forward voltage V _F is, when it comes to the forward on voltage or more values, the semiconductor rectifying element D2 is turned on, a forward current flows.

Therefore, the forward voltage _{V F} is set to the following values _{V Fon.}

V _F <V _Fon = 0.6 (V) ( _Expression 7)
(When the polarity of the power supply voltage is a positive power supply V _DD with V _ss as the reference potential, a forward current flows through the semiconductor rectifier element D1.)
When this forward current flows, the following problems occur.

The constant voltage V _reg fluctuates toward the power supply voltage V _ss side (absolute value is large).

_{-Since the} constant voltage V _reg fluctuates, the capacitance value parasitic on the semiconductor rectifier element of the electrostatic protection circuit section fluctuates and the frequency voltage deviation increases.

・ The constant voltage V _reg changes to the power supply voltage V _ss side (large in absolute value), so that the current consumption of the oscillation circuit increases.

  • When the semiconductor rectifier element D2 is completely turned on, the oscillation of the oscillation circuit stops.

The constant voltage V _reg for bypass to which the electrostatic protection circuits 200-1 and 200-2 are connected so as not to turn on the semiconductor rectifier element D2 so as not to cause such a failure is the above ( _Formula 6). ) And (Equation 7) must be set to values satisfying the above.

Here, in the case of a rechargeable timepiece, since the power supply voltage V _ss is about −2 V, the constant voltage V _reg satisfying the above (Equation 6) and (Equation 7) is given by the following equation. That is, in order not to cause the above problem, it is necessary to set the bypass constant voltage V _reg so as to satisfy the following equation.

More specifically, the constant voltage V _reg for bypass is set so as to satisfy the following expression within an expected operation range (for example, within a range of 1.2 to 2 V) as a voltage range of the power supply voltage V _{ss in which} the oscillation circuit can operate. The value of must be set.

│V _reg │> │V _ss │-V _R -V _Fon = 1.4 (V) -V _R (Expression 8)
By adopting the above configuration, according to the present embodiment, a leakage current is generated between the signal (for example, input / output terminals 71-1 and 71-2) of the oscillation circuit 40 and the line 73 of the power supply voltage V _ss. Even if it occurs, the semiconductor rectifier 72 is not turned on due to voltage fluctuations in the signal path (input / output terminals 71-1 and 71-2) of the oscillation circuit 40 due to this leakage current. As a result, even when the leakage current is generated, the oscillation circuit can be stably oscillated.

In the above description, the case where the polarity of the power supply voltage V _ss is negative with respect to the reference potential has been described as an example. On the contrary, the polarity of the power supply voltage is positive with respect to the reference potential. The present invention can be similarly applied to. Even in such a case, by setting the reference potential to V _ss and setting the bypass constant voltage V _reg so as to satisfy the above (Equation 8) within the expected operation range of the power supply voltage V _DD , the semiconductor rectifier element It is possible to prevent the occurrence of a situation in which the forward current flows when D1 (74) is turned on, and the oscillation circuit can be driven stably. (In this case, V _{ss in Equation} 8 becomes V _DD .)
Further, as described above, the constant voltage V _reg2 of the oscillation circuit 40 and the bypass constant voltage V _{reg1 of} the electrostatic protection circuits 200-1 and 200-2 are the same using the common constant voltage generation circuit 32. If the voltage is constant, there is a problem that the driving constant voltage of the oscillation circuit 40 cannot be set small for the purpose of reducing the current consumption of the oscillation circuit 40.

That is, when a bypass for constant voltage V _{re g1} of the electrostatic protection circuit 200-1 and drive constant voltage V _reg2 of the oscillation circuit 40 and the same, unless the large V _R of (8), That is, unless a circuit board having a large insulation resistance is used, the constant voltage V _reg2 cannot be set small for the purpose of reducing the current consumption of the oscillation circuit 40.

To solve such a problem, bypass constant voltage V _reg1 is preferably set as a different constant voltage to the driving predetermined voltage V _reg1 of the oscillation circuit 40. Specifically, as shown in FIGS. 2 to 4, separate constant voltage generation circuits 32-1 and 32-2 are used, and the bypass constant voltage V _reg1 and the oscillation circuit drive constant voltage V _reg2 are respectively set. It is preferable to produce them separately. The bypass constant voltage V _reg1 supplied to the constant voltage generation circuit 32 is set so as to satisfy the above ( _Equation 8), and the constant voltage V _reg2 supplied for driving the oscillation circuit 40 is further set to the oscillation circuit 40. It is preferable to set the absolute value to a small value so as to be optimal for low power consumption. By doing so, it becomes possible to achieve both low current consumption and low power consumption of the oscillation circuit 40 and stability of the oscillation frequency of the oscillation circuit 40.

That is, the output V _reg1 of the constant voltage generating circuit 32-1 is set so as to satisfy the above ( _Equation 8) and connected to the electrostatic protection circuits 200-1 and 200-2. The output V _reg2 of the constant voltage generating circuit 32-2 is set to a small absolute value so as to be optimal for reducing the current consumption of the oscillation circuit 40 and connected to the oscillation circuit 40. By doing so, it is possible to achieve both low current consumption of the oscillation circuit 40 and stability of the oscillation frequency of the oscillation circuit 40.

  In addition, when there are multiple constant voltage generation circuits, the constant voltage of the electrostatic protection circuit and the constant voltage of the oscillation circuit are set separately to oscillate the effects of transient constant voltage fluctuations caused by the discharge current when static electricity is applied. It is also possible not to give it to the circuit.

However, the bypass constant voltage V _{reg1 of} the electrostatic protection circuits 200-1 and 200-2 and the driving constant voltage V _reg2 of the oscillation circuit 40 must satisfy the following condition ( _Equation 9). (If (Equation 9) is not satisfied, when the oscillation circuit normally oscillates, a forward current flows through the semiconductor rectifier D2 each time the oscillation output reaches the V _reg2 level.)
│V _reg1 │> │V _reg2 │ ・ ・ ・ (Equation 9)
That is, as shown in FIGS. 2 to 4, when the bypass constant voltage V _reg1 is generated as a constant voltage supplied separately from the constant voltage V _reg2 supplied as the power supply voltage of the oscillation circuit 40, The bypass constant voltage V _reg1 and the driving constant voltage V _{reg2 of} the oscillation circuit 40 are set so as to satisfy the condition ( _Equation 9). As a result, it is possible to achieve the two problems of reducing the current consumption of the oscillation circuit and the stability of the oscillation frequency.

As described above, in the present embodiment, the same constant voltage V _reg may be provided to the electrostatic protection circuits 200-1 and 200-2 and the oscillation circuit 40, and the low current consumption of the oscillation circuit For this purpose, the bypass constant voltage V _reg1 and the drive constant voltage V _reg2 set separately as described above may be provided.

5-2: Second Embodiment Further, it is preferable to use a constant voltage having a temperature characteristic with small voltage fluctuation with respect to a temperature change as the bypass constant voltage V _reg1 used in the circuit of the present invention. Details will be described below.

As shown in FIG. 13, the driving constant voltage V _reg2 of the oscillation circuit 40 is set so that the gradient and the temperature characteristic of the oscillation stop voltage V _sto of the oscillation circuit 40 are equal.

This satisfies the condition of (Equation 10) so that the oscillation of the oscillation circuit 40 does not stop in the guaranteed operating temperature range of the oscillation circuit 40, and further, the constant voltage V _{reg2 is reached} to the limit for reducing the current consumption of the oscillation circuit 40 Is set to a small value close to the oscillation stop voltage.

このことは、発振回路４０の発振停止電圧Ｖ_stoの温度特性が大きい場合には、発振回路４０の駆動用定電圧Ｖ_reg2の温度特性も同様に大きくなることを意味する。

This means that when the temperature characteristic of the oscillation stop voltage V _sto of the oscillation circuit 40 is large, the temperature characteristic of the driving constant voltage V _reg2 of the oscillation circuit 40 also increases.

Therefore, when the oscillation drive constant voltage V _reg2 is used as the bypass constant voltage V _reg1 of the electrostatic protection circuit 200, the parasitic capacitance of the semiconductor rectifier element of the electrostatic protection circuit 200 also varies greatly due to temperature changes. As a result, the oscillation frequency of the oscillation circuit 40 also fluctuates, which causes a problem that the oscillation stability of the oscillation circuit decreases.

Therefore, in the circuit of the present embodiment, as shown in FIGS. 2 to 4, the constant voltage V _reg2 for driving the oscillation circuit and the constant voltage V _reg1 for bypassing the electrostatic protection circuit 200 are generated as different constant voltages. To do. In addition, as the bypass constant voltage V _reg1 , a constant voltage having a temperature characteristic smaller than that of the driving constant voltage V _reg2 of the oscillation circuit is used. As described above, by using a constant voltage having a small temperature characteristic as the bypass constant voltage V _reg1 , the parasitic capacitance fluctuation of the semiconductor rectifying element of the electrostatic protection circuit 200 in the operation guarantee temperature range of the oscillation circuit 40 can be suppressed. The stability of the oscillation frequency of the oscillation circuit 40 can be improved.

As the bypass constant voltage V _reg1 having a small temperature characteristic, it is preferable to use a driving constant voltage V _reg1 of the temperature sensor 400 as shown in FIG. 2, for example. Such a driving constant voltage V _reg1 for the temperature sensor 400 has a temperature characteristic gradient of 1 mv / ° C. or less in order to accurately measure the temperature without being affected by the ambient temperature change. Is set to For this reason, even when the ambient temperature varies, the voltage hardly changes.

FIG. 14 shows an example of a constant voltage generation circuit for generating a temperature sensor driving constant voltage V _reg1 having a small gradient of temperature characteristics.

In this constant voltage generating circuit 32-1, I262 and the N _ch transistor of I263 Yes constituted by the same size, I262 and a current amplification factor of the transistors of I263 is

となる。又、Ｉ２６２はデプレッション型、Ｉ２６３はエンハンスメント型であり、閾値電圧は

It becomes. I262 is a depletion type, I263 is an enhancement type, and the threshold voltage is

となる。この場合、定電圧発生回路３２−１の出力Ｖ_reg1は以下の式のようになり、Ｉ２６２及び、Ｉ２６３の閾値電圧差をもつ定電圧Ｖ_reg1が生成される。

It becomes. In this case, the output V _reg1 of the constant voltage generating circuit 32-1 is expressed by the following equation, and a constant voltage V _reg1 having a threshold voltage difference of I262 and I263 is generated.

トランジスタＩ２６２及び、Ｉ２６３の閾値電圧は同一の温度特性を持つため、閾値電圧差は変化せず、温度に依存しない定電圧Ｖ_reg1が生成される事になる。

Since the threshold voltages of the transistors I262 and I263 have the same temperature characteristics, the threshold voltage difference does not change and a constant voltage V _reg1 independent of temperature is generated.

However, the constant voltage V _reg1 of the electrostatic protection circuit and the constant voltage V _reg2 of the oscillation circuit need to satisfy the above conditions ( _Equation 8) and ( _Equation 9).

5-3: Third Embodiment As shown in FIG. 15, for example, assuming that a static voltage of a negative polarity is applied to the circuit of this embodiment, the static electricity of the negative polarity is electrostatically charged. A discharge path 1000 for discharging to the bypass constant voltage V _reg1 side through the protection circuit (first semiconductor rectifier element) 200 is formed.

For this reason, in the circuit of the present embodiment, when there are a plurality of constant voltage generation circuits 32 that supply a constant voltage, the constant voltage drive region (scale of the entire circuit driven by the constant voltage) has a larger constant voltage. It is preferable to use the constant voltage of the voltage generation circuit 32 as the bypass constant voltage V _reg1 for the electrostatic protection circuit. Details will be described below.

  In FIG. 15, D3 schematically represents an equivalent circuit of the entire circuit (excluding the electrostatic protection circuit 200) driven by the constant voltage generation circuit 32 at a constant voltage. Since the circuit driven at a constant voltage is basically composed of a semiconductor, it is equivalently represented as a parasitic diode D3 as shown in FIG.

  As the number of circuits driven by the constant voltage increases, the capacitance of the parasitic diode D3 equivalently expressed as described above also increases.

  Here, the increase in the number of circuits driven by constant voltage and the increase in the capacitance of the parasitic diode D3 is said to increase the constant voltage drive region. The semiconductor rectifier element D3 represents a parasitic diode that can be formed in a constant voltage drive region.

  When negative polarity static electricity is applied, the discharge path 1000 is generated using the avalanche phenomenon of the parasitic diode D3.

  At this time, as described above, when the circuit scale driven by constant voltage, specifically, the constant voltage drive region is large, the area of the parasitic diode D3 shown in FIG. As a result, the discharge capability is increased, and the antistatic characteristics of the parasitic diode D3 are also improved.

For the above reasons, when there are constant voltages supplied from a plurality of constant voltage generation circuits 32, the constant voltage V _reg1 for bypass is a constant voltage drive region (circuit scale driven by constant voltage). It is preferable to use a larger constant voltage.

  In addition, in order to improve the anti-static property, the semiconductor rectifying element D4 is intentionally connected in parallel to the constant voltage generating circuit 32 separately from the parasitic diode D3, and this is used as a part of the discharge circuit 1000. May be adopted.

Even in this case, the bypass constant voltage V _{reg1 of} the electrostatic protection circuit 200 and the driving constant voltage V _reg2 of the oscillation circuit 40 need to satisfy the above conditions ( _Equation 8) and ( _Equation 9).

5-4: Fourth Example Although the embodiment of this case has been described assuming that the positive power source V _DD is the reference potential and the power source voltage V _ss and the constant voltage V _reg have negative polarity, the present invention is a negative power source. The present invention can also be applied to a configuration in which V _ss is a reference potential and the power supply voltage V _DD and the constant voltage V _reg are configured with a positive polarity.

(6) Others In each of the above-described embodiments, the semiconductor rectifying element is described by using a diode as an example, but other than this, a protection circuit may be formed using various semiconductor rectifying elements as necessary. Can do. For example, as shown in FIG. 10, an electrostatic protection circuit may be formed using a bipolar transistor as a semiconductor rectifier.

  In the above-described embodiment, the case where the present invention is applied to a portable wristwatch is described as an example. However, the oscillation circuit and the electrostatic protection circuit of the present invention are not limited to this, for example, various electronic devices such as a portable wristwatch. It may be used as a reference signal source in various electronic devices such as telephones and portable computer terminals, and may be applied so as to drive a drive unit (circuit) of each electronic device based on an output signal of the reference signal source.

FIG. 1 is a block diagram showing an example of an electronic circuit for a wristwatch to which the present invention is applied. FIG. 2 is a block diagram showing an example of a clock circuit portion of the electronic circuit shown in FIG. FIG. 3 is a block diagram showing another embodiment of the timepiece circuit portion. FIG. 4 is a block diagram showing another embodiment of the timepiece circuit portion. FIG. 5 is an explanatory diagram showing voltage fluctuations of two types of power supplies used in the circuit of this embodiment. 6A is an equivalent circuit diagram of the crystal oscillation circuit of FIG. 2, FIG. 6B is an explanatory diagram of the crystal resonator, and FIG. 6C is an equivalent circuit diagram of the crystal resonator. (D) is an equivalent circuit diagram of FIG. (A) created in consideration of an equivalent circuit of a crystal resonator. FIG. 7 is an explanatory diagram of another electrostatic protection circuit. FIG. 8 is an explanatory diagram of a conventionally used electrostatic protection circuit. FIG. 9 is an equivalent circuit diagram of the electrostatic protection circuit shown in FIG. FIG. 10 is an explanatory diagram of an electrostatic protection circuit configured using other types of semiconductor elements. FIG. 11 is an explanatory diagram of the arrangement of the crystal resonator and the C-MOS-IC constituting the main part of the oscillation circuit on the substrate. FIG. 12 is an equivalent circuit diagram when a leakage current occurs between the signal path of the oscillation circuit and the power supply voltage line. FIG. 13 is an explanatory diagram showing temperature characteristics of the oscillation stop voltage and the oscillation drive constant voltage in the operation guarantee temperature range of the oscillation circuit. FIG. 14 is a schematic explanatory diagram of a constant voltage generation circuit for driving a temperature sensor. FIG. 15 is an explanatory diagram of a discharge path when static electricity having a negative polarity is applied.

Claims (14)

A first static voltage connected between the signal path of the oscillation circuit and the constant voltage side and bypassing the first polarity static voltage entering the signal path to the bypass constant voltage side via the first semiconductor rectifier element. An electrical protection circuit;
A second electrostatic protection circuit that is connected between the signal path and the reference potential side and bypasses the second polarity static voltage entering the signal path to the reference potential side via a second semiconductor rectifier element. When,
Including
When the main power supply voltage is V _ss , the forward ON voltage of the semiconductor rectifier element is V _Fon , and the potential difference between the signal path and the power supply voltage line when a leakage current occurs is V _R ,
The bypass constant voltage V _reg is within the range of the expected operation voltage of the main power supply voltage | V _ss |
Next formula
│V _reg │> │V _ss │-V _R -V _Fon
An oscillation circuit characterized by being set to a value satisfying In claim 1,
The constant voltage for bypass is
An oscillation circuit, characterized in that it is a constant voltage V _reg1 supplied separately from the constant voltage V _reg2 supplied as a power supply voltage of the oscillation circuit. In claim 2,
The bypass constant voltage V _reg1 and the constant voltage V _reg2 supplied as the power supply voltage of the oscillation circuit are:
│V _reg1 │> │V _reg2 │
An oscillation circuit characterized by being set so as to satisfy the above condition. In any one of Claims 1-3,
Supplying a constant voltage and one V _reg2 of the supply constant voltage a partial pressure-boosted obtained constant voltage from the constant voltage supply circuit used as a power supply voltage of the oscillator circuit, using the other V _reg1 as the bypass constant voltage An oscillation circuit characterized by that. In any one of Claims 1-4,
As the bypass constant voltage,
An oscillation circuit characterized by using a constant voltage having a temperature characteristic in which a voltage variation with respect to a temperature change is smaller than a constant voltage supplied as a power supply voltage of the oscillation circuit. In any one of Claims 1-5,
Between the output of the constant voltage supply circuit for supplying the constant voltage for bypass and the reference potential, a static voltage of the first polarity that enters the signal path is passed through the first semiconductor rectifier element. An oscillation circuit comprising a discharge semiconductor rectifier for discharging to a voltage side. In claim 6,
An oscillation circuit characterized in that the discharging semiconductor rectifier element is a parasitic diode. In any one of Claims 1-7,
The first electrostatic protection circuit includes:
And a third semiconductor rectifier element connected between the signal path of the oscillation circuit and the main power supply and configured to bypass the first polarity static voltage entering the signal path to the main power supply voltage side. Oscillator circuit. In claim 8,
The parasitic capacitance value of the third semiconductor rectifier element is
An oscillation circuit, wherein the oscillation circuit is set to a value smaller than a parasitic capacitance value of the first semiconductor rectifier element. In any one of Claims 1-9,
An oscillation circuit characterized in that a part or all of the parasitic capacitance of each semiconductor rectifier element is used as a phase compensation capacitor.   11. An electronic circuit comprising: the oscillation circuit according to claim 1; and a drive circuit that drives a driven portion based on an output of the oscillation circuit.   A semiconductor device comprising: the oscillation circuit according to claim 1; and a circuit board on which the oscillation circuit is mounted.   11. An electronic timepiece comprising: the oscillation circuit according to claim 1; and a time display unit that displays a time based on the oscillation circuit.   An electronic apparatus comprising: the oscillation circuit according to claim 1; a drive circuit that drives a driven unit using an output of the oscillation circuit; and a driven unit.

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