JPS62299109A - Oscillation circuit - Google Patents

Abstract

PURPOSE:To attain the temperature correction by a component itself of the oscillation circuit by making each resistance-temperature characteristic of the 2nd resistor whose one terminal is connected to an output stage of a CMOS inverter and of the 1st resistor dividing a reference voltage different from each other in a relation to cancel the temperature-frequency characteristic of the oscillator circuit itself. CONSTITUTION:Since resistors 11, 12 are P<+> resistors and a resistor 13 is a P<-> resistor, the rate of fluctuation of the resistor 13 with respect to temperature is larger than that of the resistors 11, 12. Thus, an H level reference voltage at a high temperature is lower than that at room temperature, an L level reference voltage is higher than that at room temperature, conversely an H level reference voltage at a low temperature is higher than that at room temperature and the L level reference voltage is lower than that at room temperature. The difference between the H and L level reference voltages at a high temperature is smaller than that at room temperature and the difference at low temperature is larger than that at room temperature. Thus, the charge/discharge time at each period is shorter at high temperature than that at room temperature and longer at low temperature and the oscillated frequency fos is faster at high temperature and slower at low temperature.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The oscillation circuit with a temperature correction function of the present invention is particularly applied to a CR type oscillation circuit, and this oscillation circuit can be integrated into an IC. When I did,
External attachment for temperature correction eliminates the need for an element or a dedicated terminal for it.

[Conventional technology]

In a system using an oscillation circuit, various controls are performed based on the oscillation frequency. Therefore, higher precision of the oscillation frequency is required. In such cases, a crystal oscillator or a ceramic oscillator is used as the oscillation element. However, these devices have the disadvantage of high cost. Moreover, in automotive systems -40 to +10"C
Although stable operation is required in the temperature range of Therefore, when an inexpensive system is required, a C-R oscillation circuit using resistors and capacitors is used.

[Problem that the invention seeks to solve]

The disadvantages of this circuit are that the oscillation frequency accuracy at room temperature is somewhat poor and that it has temperature characteristics. The oscillation frequency at room temperature can be adjusted by adjusting external elements. Fluctuations in oscillation frequency due to temperature usually decrease as the temperature rises, and this is largely due to the temperature characteristics of the internal circuit, and countermeasures require additional changes to external elements and circuits, increasing costs and amplifiers. becomes.

In view of the above points, it is an object of the present invention to provide a CR-type oscillation circuit that can eliminate the need for an external element for temperature correction or a dedicated terminal for it, and can sufficiently reduce the temperature characteristics of the oscillation frequency. .

[Means for solving problems]

Therefore, the present invention provides a charging and discharging CR circuit, a reference voltage circuit that forms first and second reference voltages, and a comparator that operates by comparing the charging and discharging voltage of this CR circuit with one of the first and second reference voltages. , and a CMOS type inverter that switches to the other of the first and second reference voltages according to the output of the comparator, the reference voltage circuit comprising a plurality of reference voltage circuits connected in series to a constant voltage source. a first resistor and an intermediate portion of the first resistor and the CMO
and a second resistor connected to the output stage of the S-type inverter, and the first and second resistors are selected to have different resistance-temperature characteristics.

〔Example〕

Next, examples of the present invention will be described. In FIG. 1, A indicates the IC device side, and terminal S1 for external connection.
, S2. Of the resistors 11, 12, and 13 that determine the reference voltage of the oscillation comparator l on the IC element side, 11 and 12 are P° diffused resistors, and 13 is a P- diffused resistor.

The resistance value of each resistor is set to a desired value.

(For example, R1 = R, = 50 = Ω, Rz = 25 = Ω).

The ON l of the P-channel MOS transistor 3A of the CMOS type inverter 3 is R4, and its n-channel M
O3) Let R3 be the ON resistance of transistor 3B. Ra,
The value of Rs should be made sufficiently smaller than the resistance values R8 to R3 of the reference voltage forming resistors 11 to 13 (for example, 0.
(25 kΩ or less). Resistor 10 forming a CR circuit for charging and discharging
．． Capacitor 2o is externally attached. Note that 0° does not indicate a constant voltage source.

The P° diffused resistor 11, 12 and the P- diffused resistor 13 have different diffused resistance concentrations. In general, the P-resistance has a lower P-resistance diffusion concentration (the sheet resistance value is higher), and the rate of change in resistance value with temperature is greater in the P-resistance (see Figure 6).

The ON resistance of both transistors 3A and 3B of the inverter 3 increases as the temperature rises, but the rate of change from room temperature is several tens of percent in the temperature range of -40 to 150 degrees Celsius.
Therefore, if the initial value is small enough, it will be within the error range.

The temperature characteristics of the element values of the external resistor 10 and capacitor 20 can be made sufficiently small by selecting the elements, and in this case can be ignored for convenience.

Therefore, the reference voltage on the (+) large saw (non-inverting input) side of the oscillation comparator 1 is as follows.

(i) When the output of comparator l is at H level (that is, high voltage output)...When the H level reference voltage is generated, the output of inverter 3 is at H level, and at that time, transistor 3A of inverter 3 is ONL, transistor 3B turns off. Therefore, the potential Val at point a, which enters the (+) input of comparator 1, is represented by the equivalent circuit shown in FIG. That is, Va.

=R,・VDn/ (Rz +R1(R3+Ra)/
(R1+R3+R4)).

(11) When the output of comparator 1 is at L level (that is, low potential output)... When the L level reference voltage is generated, the output of inverter 3 is at L level, and at that time, transistor 3A
is OFF, and 3B is ON. Therefore, the potential ■a2 at point a, which enters the (+) input of the comparator 1, is represented by the equivalent circuit shown in FIG. That is, Va2 = (Rz (
R3+Rs) ・Vo.

/ (Rz ”R3+Rs) l / (R+ +R
2(R30R5)/(R2+R3+R5)l.

Here, R3-R3 is each transistor 3 of the inverter 3.
Since the ON resistance values R= and Rs of A and 3B are sufficiently large compared to each other, the influence of R4 and Rs can be reduced. For example, R,
=R3=50Ω, R,=25Ω, R4, Rs ≦0
．． If Ω is set to 25, the contribution rate of R4 and R3 will be 1% or less.

Oscillation frequency f. Factors that cause temperature-related fluctuations in S include the following.

(1) Operating speed of comparator I (when output is inverted) Generally, the operating speed decreases as the temperature rises. The constant current in the circuit generally has a negative temperature coefficient, and this is a major cause of fluctuations in operating speed. Also, the transistor switching speed within the circuit decreases with increasing temperature.

As is well known, this is determined by the temperature characteristics of the threshold voltage (7) and the mobility μ of the MoS transistor.

(2) Operating speed of inverter 2.3 (when output is inverted) As explained above, the switching speed of the transistor decreases as the temperature rises. Therefore, like the comparator 1, the operating speed during output inversion (L-II and HL) decreases as the temperature rises. On the contrary, it becomes faster when the temperature decreases.

(3) Stray capacitance due to absolute value fluctuations of resistance values R1 to R3 (
Since the resistance value of the operating speed diffused resistors 11 to 13 has a positive temperature coefficient with respect to the wiring capacitance, junction capacitance, etc., the resistance value increases as the temperature rises. Therefore,
Due to the stray capacitance, the switching speed of the reference voltage level when voltage is applied to the resistor 13 decreases as the temperature rises.

When the resistors 11 to 13 are composed of the same type of resistors, the temperature change rate of the resistors is almost the same, so the H level and L level reference voltages input to the comparator 1 hardly change. If the input offset voltage of comparator 1 is stable during one cycle of oscillation, it will be canceled out, so the influence is very small.

From the above, if the resistors 11 to 13 are composed of the same type of resistors, from the above (11 to (3)), the oscillation frequency fa
s fluctuates greatly with respect to temperature fluctuations, and the fluctuation of the oscillation frequency from room temperature Δ".5 is shown in FIG.

In other words, it decreases on the high temperature side and increases on the low temperature side.

On the other hand, in this embodiment, since the resistors 11.12 and 13 are P-resistances, the rate of variation with respect to temperature of the resistors 13 is larger than that of the resistors 11.12.

Therefore, on the high temperature side, the H level reference voltage is lower than that at room temperature, and the L level reference voltage is higher than that at room temperature. Conversely, on the low temperature side, the H level reference voltage is higher than that at room temperature, and the L level reference voltage is lower than that at room temperature (
Become.

As shown in FIG. are raised to the LL/Hel reference voltage, each 11, but this cancels out.

In this embodiment, the difference between the H level and L level reference voltages on the high temperature side is smaller than that at room temperature. On the low temperature side, the opposite is true.

Therefore, the charging/discharging time in each cycle is shorter on the high temperature side (and longer on the lower temperature side) compared to room temperature. In other words, the oscillation frequency f as is faster on the higher temperature side and slower on the lower temperature side. do.

Therefore, if the types and resistance values of the resistors 11 to 13 are determined in accordance with the temperature characteristics shown in (11 to (3)) above, the desired temperature characteristics of the oscillation frequency can be obtained.

Next, other configuration examples of the resistors 11 to 13 will be shown below.

+11 11.127N” resistance, 13:P” resistance (21
11, 12: Polysilicon resistance, llr” resistance + 3111.12: Polysilicon resistance, 13: N” resistance + 4111.12: Polysilicon resistance, 13: P-resistance (fi) 11.12: N” Resistance, 13: P-resistance Each of the above-mentioned resistances and each resistance of the first embodiment may be a diffused resistance or a resistance formed by ion implantation.

Further, although the above-described resistor configuration is designed to make the oscillation frequency faster on the high temperature side, it is also possible to make the oscillation frequency slower on the high temperature side by reversing the combination of resistors.

Further, each or both of the oscillation resistor IO and the capacitor 20 may have a built-in tC, or 1O120 may have a temperature characteristic.

Further, the (+) and (-) M multiple inputs of the comparator 1 may be reversed. However, in that case, in order to match the logic (operation), an inverter may be added or removed from the comparator output.

Also, for the inverter 2.3, it is acceptable to use a powerful opening, reduction, etc. (as long as there is logic). A delay circuit or the like may be provided. Further, the comparator 1 may be replaced with an operational amplifier or a Schmitt trigger circuit.

Also, the current capacity (transistor size) of inverter 3
may be set arbitrarily depending on the purpose.

Further, this may be replaced with a switch circuit (analog switch, etc.).

Further, (+) and (-) of the reference voltage source may be of different potentials generated from the power supply of the IC.

Alternatively, it may be obtained from a separate power source. The same applies to the (-) (ground potential in this case) power supply of the capacitor 20.

Moreover, each of the resistors 11-13 may be configured with a plurality of resistors in series or in parallel instead of one each. In this case, resistors having different temperature characteristics may be combined.

Also, the oscillation frequency can be changed to any part of the circuit (
It can be extracted from the part that is oscillating.

Although the above explanation has been made using a two-terminal oscillation circuit, the present invention can also be applied to an l-terminal oscillation circuit as shown in FIG.

In this case, all the various examples mentioned above can also be applied. In addition, 5 is an N-channel MO for discharging the capacitor 20.
It is an S transistor.

〔Effect of the invention〕

As described above, in the present invention, the resistance-temperature characteristics of the first resistor that divides the reference voltage and the second resistor whose one end is connected to the output stage of the CMOS inverter are made different, and the oscillation circuit itself The temperature-frequency characteristics of the oscillation circuit are set in a relationship that cancels each other out (thereby, the temperature can be corrected in the constituent elements of the oscillation circuit itself, and an external element for temperature correction or a dedicated terminal for it can be eliminated.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, FIGS. 2 to 6 are diagrams used to explain the operation of the present invention, and FIG. 7 is a circuit diagram showing another embodiment of the present invention. be. l...Comparator, 2.3...0MO8 type inverter, 11.12...P'resistance 13...P'resistor I
O: External resistor for oscillation, 20: External capacitor for eye development. Representative Patent Attorney Takashi Okabe 20 Voe i external attachment code) de)suVo e aras (÷) Denzui, Dengo↑os, BonkiVglaretL number Fig. 2 (+)

Claims (1)

[Claims] A charging and discharging CR circuit, a reference voltage circuit that forms first and second reference voltages, and a charging and discharging voltage of this CR circuit that forms the first and second reference voltages.
An oscillation circuit comprising: a comparator that performs a comparison operation with one of the reference voltages; and a CMOS inverter that switches to the other of the first and second reference voltages in accordance with the output of the comparator, the reference voltage circuit comprising: , a plurality of first resistors connected in series to a constant voltage source, and a second resistor connected to an intermediate portion of the first resistors and an output stage of the CMOS type inverter; An oscillation circuit characterized in that the two resistors are selected to have different resistance-temperature characteristics.