JPH03163902A - Oscillation circuit - Google Patents

Abstract

PURPOSE:To reduce the current consumption of an oscillation circuit without lowering a power supply voltage at an LSI equipped with a timer function by providing a resistance switching means to change a resistance value between a vibrator and the terminal of a driving means and making the resistance value of the said resistance switching means smaller than a resistance value at the time of turning on a power source after oscillation is made stable. CONSTITUTION:Between a node B and a node C, the resistance switching circuit serially connecting a second dumping resistor Rd and a switch MOSFET M1 is formed parallelly with a dumping resistor RD. A power source turn-on detecting circuit VDC is composed of a time constant circuit serially connecting a resistor R1 and a capacitor C1 between a power supply voltage terminal Vc and a ground point GND. Since the time constant of this CR time constant circuit is suitably set, the level of an output signal CNT exceeds the threshold voltage of the switch MOSFET M1 and this is turned ON after the lapse of fixed time to turn on the power source. When the MOSFET M1 is turned ON, the second dumping resistor Rd is connected and the resistance value between the node B and the node C is decreased from RD to RD.Rd/(RD+Rd).

Description

[Detailed description of the invention] [Usage of industry 1-! I'F ] The present invention is based on oscillation technology using a vibrator, and furthermore, on low-frequency oscillation circuits. Regarding technology that is particularly effective when applied to l'l cost current conversion,
For example, it relates to technology that can be effectively applied to a single-chip microcontroller using the Kano01 function.

[Conventional technology] Single-chip microcontrollers used in home appliances, etc.
■II X'7. IJl is a 4-bit 1 single-chip microcontroller manufactured by Seisakusho that allows you to remove the Mizushima oscillator like Il1)/104608! There is one that has a vibration circuit and a built-in function. When ■1 Move the function to the right l. ，
In ST, it is necessary to continue operating by supplying battery voltage to the oscillation 1i1 circuit. 1
The current consumption increases.

For example, there is a circuit shown in No. 51 No. 1 as an example of a circuit installed in a single-chip microcomputer that performs the N1 function.

In the same figure, C to apply
MOS inverter, R is a feedback resistance, and RD is a damping resistance. Of the two elements, the inverter INV, feedback resistance RF, and damping resistance Rl
) are often built into the chip. The damping resistor RD shifts the phase between nodes B and C to facilitate oscillation, and also serves to suppress the transient current to the crystal oscillator X when the power is turned on, and is generally around 500 KΩ. It is said that

[Problems to be solved by the invention] Conventionally, in order to reduce the current consumption in LSIs with built-in oscillation circuits as described above, the current flowing through a MOS transistor is proportional to the square of the applied power supply voltage. For this reason, the power supply voltage Vc supplied to the oscillation circuit has been clamped and lowered for each step.

However, if the power supply voltage Vc is lowered too much, the inverter will no longer operate, so there is a limit to the method of lowering the power supply voltage.

An object of the present invention is to provide an oscillation control technique that can reduce the current consumption of an oscillation circuit without lowering the power supply voltage.

The description and other objects and novel features of this invention will become apparent from the description of this specification and the accompanying drawings.

[Means for Solving the Problems] A typical summary of the inventions disclosed in this application is as follows.

Prior to filing this application, the present inventor conducted various studies on reducing the current consumption of an intervening circuit using methods other than power supply voltage. First, in the vibration state, the inverter INV repeatedly charges the external capacitor Cn via the damping resistor R, so the damping resistor R is
Thinking that the force of increasing the resistance value of D could reduce the current consumption, we conducted an experiment in which the oscillator circuit was operated by changing the damping resistor Ro. As a result, it has been found that reducing the damping resistor 12n can actually reduce the current consumption. However, at the start of oscillation, a somewhat large resistance is required.

3 This was done based on the knowledge of the wooden invention, and a resistance switching circuit is provided at the damping resistor connection part, so that the damping resistor is connected as is when the power is turned on, and the resistance of the damping resistor is lowered after the oscillation stabilizes. It is proposed to control a resistance switching circuit.

The control signal of the switching path IIl is 1! It is advisable to provide a power supply detection circuit to enable the power supply to be turned on, or to provide a reset signal or standby signal for the microcomputer.

[Function] The input/output nodes A and B of the inverter rNV have the same voltage due to the feedback resistor 12F, and by connecting the water resonator X, the oscillation state is maintained at a certain frequency. At this time, node B is swinging from the ground potential to the power supply voltage Vc level by turning on and off the inverter INV.

On the other hand, as shown in FIG. 6, experiments have shown that the cap of node A becomes smaller when the damping resistor 12r) is changed significantly. Since the Mizushin oscillation circuit uses the mechanical vibration of the oscillator, it is difficult to explain it theoretically = 4. However, as the damping resistance Rn increases, the voltage applied to both ends of the Mizushin oscillator X decreases, and the node A It is thought that the size of the hat will also become smaller. Therefore, when the damping resistor (Rr) is made smaller, the inverter's input voltage becomes larger and the through current is reduced, thereby reducing the current consumption of the oscillation circuit.

[Embodiment] FIG. 1 shows a first embodiment of an oscillation circuit according to the present invention.

In the same figure,
V is a CMOS inverter as a driving means for applying voltage between the picture terminals of Ryo Mizushina, RF is a feedback resistor, +
2 r> is a damping resistance.

In this embodiment, a low resistance switching circuit RCC in which a second damping resistor Rd and a switch MOSFEi'M are connected in series is provided between the node r3 and the node C in parallel with the damping resistor Rn. There is. And, at the gate terminal of the switch MOSFET M, there is a power supply input detection circuit VI for detecting the rise of the power supply voltage Vc.
A control signal % C N 1' from C is applied. The power-on detection circuit V I) C is a resistor 1 connected between the power supply voltage terminal V c and the ground point GN I), for example.
It also consists of a time constant circuit in which and a capacitor (, and When the level of the signal C N i' is 1", the switch MO S I"r-:'FM, threshold 4l'F
? fj I:l:. Exceeds and turns this on. When MO S FE i' M is turned on, the second
Mr. I2 () is connected to node l
The resistance f11'[ between 3 and node C is from Rrl to [? n
・l'j d / (R n + I.'2 d
) decreases to

In addition, -1. Record BID. In the example, inverter I
NV and feedback resistance scale ", damping low resistance Rn,
12d and the switch MO S Fr”.TM, are placed inside the chip.
Cr) is said to be outside A/1. The power-on detection circuit V1)C may be built in the chip or externally {;
It may be configured with a J circuit.

Instead of providing a power-on detection circuit VDC, the microcomputer system is used for reset 1/Shinma and standby Shinso, and the switch MOSFI 2 is used to create the Gyosho circuit RCC. It may also be the control signal CNT of I″M1.

FIG. 2 shows a second embodiment of the oscillation circuit according to the present invention.

In this embodiment, a second damping resistor Rd is connected in series with the damping resistor r2n between the node r3 and the node C.
Then, a resistance switching circuit +< C is formed by connecting a switch MOSFET M in parallel with this second damping resistor Rd.
C: is crossed. ”, Written by Suizuji M CJ S
As in the first embodiment, F E 'I' M, is the control signal q CN, which is the power-on detection circuit or the detection signal of 1'-, or the reset signal or standby signal inside the microcomputer.
'1 and °C is supplied.

In this embodiment as well, when the power is turned on, the damping resistance is as high as 4j ((R r) + R d, but after the oscillation stabilizes, it decreases to R n, making it possible to reduce the current cost by ?11j).

7. FIGS. 3 and 4 show an example of an element structure in which the resistance switching circuit RCC is built into a zip.

That is, the damping resistance R D and 1≧d are formed by the NQlj well regions 2a and 2b formed parallel to the surface of the l) type semiconductor 1I (plate l).The well regions 2a and 2b are They are shaped so that one end is continuous with the other, and the continuous end is the node, that is, the inverter INV.
connected to the output terminal of

And -1. MOSF +'. N7? which becomes the source/drain region of i'M? '7 diffusion N3a, 3b is provided,
Is there a game between 3F1 and 31.1 of Diffusion? L1 pole 4 is formed.

In addition, 1. In the embodiment described, the switch MOSFE
Although TM1 is configured under an N-channel MOSFIE, it can be changed to a P-channel MOSFIE by reversing the polarity of the gate control signal CNT.

As explained in Section 7 below, in the embodiment described above, a damping resistance J replacement circuit is provided at the tamping resistance connection r11; , after the oscillation stabilizes, the tamping resistor's resistance is lowered by l.
Since the circuit is controlled, the amplitude of the inverter's input becomes larger and the through current is reduced, thereby reducing the oscillation circuit's current consumption. effective.

Hereinafter, the invention made by the Futaki Ministry of Invention has been specifically explained based on examples, but the invention is not limited to the above-mentioned examples, and changes can be made without departing from the spirit of the invention. Needless to say. For example, in the above embodiment, the resistor cutter circuit is connected to two resistor cutters, CRn and R.
RL and switch MQS F+-: i", but only one MOSFET is used to create a low-resistance f-ge circuit and control its game 1 electric current. By changing the MOS ON resistance, power on H1p7 is set high, and 5
After the δ vibration stabilizes, even if you try to control it like Kuro and Ru, it will not work.

More than that! II F is the utilization of the invention made by the present invention as 31! Although the present invention has been described as being applied to a single-chip microcomputer, it can also be applied to a circuit in an LSI or printed circuit board having the R1 function.

[Effects of the Invention] The effects achieved by typical inventions disclosed in this application are summarized in 111. The explanation is as follows.

In other words, it is possible to reduce the current consumption of the oscillation circuit without lowering the power supply voltage in an LSI having the Jiji 1 function.

[Brief explanation of the drawing]

FIG. 1 shows a first embodiment of an oscillation circuit according to the present invention.
01 circuit diagram, Fig. 2 is a circuit diagram showing the second embodiment of the oscillation circuit related to the wood-based IJJ, Fig. 3 is a plan view showing an example of the element structure of the resistor cutout circuit, and Fig. 4 is the resistor 1i1J. f'/A cross-sectional view taken along the IV-IV line in FIG. 3 showing an example of the element structure of the circuit,
FIG. 5 is a circuit diagram showing an example of a conventional oscillation circuit, and FIG. 6 is a graph showing the relationship between the value of the damping resistor and the amplitude level of the input voltage of the inverter. X: Crystal oscillator, Ro: Damping resistance. 11 = 12 Fig. 3 ``''% Me■ Shil 2b/'X+ s----''''''1 1 Straight σ\1 0 Fig. 5 RF Fig. 4 Fig. 6 Fig. Ro (Ω)

Claims (1)

[Scope of Claims] 1. In an oscillation circuit comprising a vibrator and a drive means for applying an alternating current voltage to the vibrator, a resistance switching device capable of changing a resistance value between the terminals of the vibrator and the drive means. An oscillation circuit characterized in that the resistance value of the resistance switching means is made smaller than the resistance value when the power is turned on after the oscillation is stabilized. 2. The oscillation circuit according to claim 1, wherein the driving means comprises an inverter and a feedback resistor connected between input and output terminals of the inverter. 3. The resistance switching means includes two parallel or series resistors and a switch element connected in series with one of the parallel resistors or a switch element connected in parallel with one of the series resistors. 3. The oscillation circuit according to claim 1, wherein the oscillation circuit is comprised of: