JP2007267119A - Electronic circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic circuit which is normally operated without increasing an operation margin between a switching element of a structure to resist a high voltage and a switching element to operate at a low drive voltage. <P>SOLUTION: In the electronic circuit 100, a circuit to drive by an external supply voltage constitutes the switching element by a design rule or a device structure suiting to a maximum voltage of the external supply voltage, and a circuit to drive by an internal step-down voltage constitutes the switching element by the design rule or the device structure suiting to a voltage of an internal step-down circuit. The electronic circuit 100 sets the operation margin of an output voltage value of the internal step-down voltage to a minimum by making an output switching element 108 to decide the output voltage value of a voltage output circuit constituting the internal step-down circuit set approximately the same as an electric characteristic of the switching element constituting the circuit to drive by the internal step-down circuit and achieves a low power consumption. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electronic circuit that operates with a plurality of different power supply voltages, and more specifically, includes an internal circuit that operates with an external power supply voltage and an internal circuit that generates another power supply voltage from the external power supply voltage and operates with this voltage. It has an electronic circuit.

  In portable portable electronic devices such as mobile phones and electronic watches, a primary battery or a rechargeable secondary battery is used as a main power source for driving a built-in electronic circuit. In recent years, there is a strong tendency to use a rechargeable secondary battery as a power supply means in consideration of the environment, and its use is widely spread in electronic devices such as electronic watches that are always carried.

For example, for a small electronic device equipped with a rechargeable secondary battery, it is important how long it can be operated when operated with a fully charged secondary battery.
As a measure for driving a secondary battery with a small electronic device for a longer period of time, a secondary battery having a large storage capacity may be mounted. However, such a secondary battery has a large size, and it is difficult to mount the secondary battery on a device whose size is limited, such as a small electronic device.

  In order to solve such a problem, there is a battery in which the material constituting the secondary battery is changed to increase the storage capacity without increasing the size. For example, a lithium ion battery. However, such secondary batteries tend to have higher output voltages.

Among small electronic devices, electronic watches are required to be smaller in recent years. In such an electronic timepiece, it is necessary to mount a power supply means having a smaller size in accordance with the demand for downsizing, and in recent years, electronic timepieces can be driven for a long time with a smaller power supply means. It is essential to reduce the power consumption of built-in electronic circuits.
To reduce the power consumption of an electronic circuit, the drive voltage for driving the electronic circuit may be lowered. However, as described above, an electronic timepiece often uses a secondary battery as a power supply means. In a timepiece, a secondary battery having a large storage capacity in recent years has a problem that power consumption cannot be reduced because the high output voltage is high.
That is, among secondary batteries, a secondary battery of a type that has a small size and a large storage capacity cannot be used for an electronic circuit that requires low power consumption because of its high output voltage.

  We look at many proposals to solve such problems. In particular, there is an internal voltage step-down circuit which is used by stepping down a voltage for driving an electronic circuit to a low voltage (for example, see Patent Document 1).

That is, the output voltage (drive voltage) from the power supply means is stepped down to a predetermined low voltage by the internal step-down circuit, and the electronic circuit is driven using the stepped down voltage as the drive voltage.
With such a configuration, even if a secondary battery such as a lithium ion battery having a high output voltage but a large storage capacity is used as a power supply means, the electronic circuit can reduce power consumption.

[Description of Operation of Conventional Technology: FIG. 3]
Next, the prior art shown in Patent Document 1 will be described with reference to FIG. In this prior art, power consumption is reduced by lowering the power supply voltage of a clock oscillation circuit. In FIG. 3, 301 is a pad, 302 is a regulator, 303 is a low-speed operation unit, and 304 is a low-frequency oscillator in the low-speed operation unit 303. The regulator 302 is a circuit that steps down and outputs an input voltage, and is an internal step-down circuit.

  The regulator 302 internally steps down the external power supply voltage VDD supplied from the pad 301 to the voltage VDDR. The stepped down voltage VDDR is connected to the low speed operation unit 303 and supplied to the low frequency oscillator 304. The low frequency oscillator 304 operates using the voltage VDDR that is the output voltage of the regulator 302 as a power supply voltage. For example, by setting the external power supply voltage VDD to 5V and the voltage VDDR to 2V and driving the circuit with a voltage lower than this, power consumption can be reduced.

Japanese Patent Laid-Open No. 5-264755 (2nd page, FIG. 1)

  In the prior art disclosed in Patent Document 1, the value of the external power supply voltage VDD is internally stepped down to a lower voltage VDDR by the regulator 302, and the internal circuit is consumed by driving the internal circuit with this low voltage. However, the external power supply voltage VDD is applied to the regulator 302 as it is.

  By the way, an electronic circuit mounted on an electronic timepiece is often composed of a semiconductor integrated circuit. This is because it is more widely used because it can cope with lower power consumption when integrated on one semiconductor integrated circuit than when a circuit is constructed by collecting independent circuit components.

  The prior art disclosed in Patent Document 1 also assumes a case where the circuit is configured by a semiconductor integrated circuit. As described above, since the external power supply voltage VDD applied to the regulator 302 is higher than the voltage VDDR that is a stepped down voltage, when the electronic circuit is configured with a semiconductor integrated circuit, the regulator 302 is The switching element to be configured needs to have a semiconductor element configuration sufficient to withstand this external power supply voltage VDD. That is, it is necessary to design the switching element with a design rule or device structure corresponding to the maximum operating voltage.

  As is well known, a semiconductor integrated circuit integrates many semiconductor elements on a single semiconductor substrate and performs film formation, impurity introduction, wiring formation, and the like at the same time. Therefore, all semiconductor elements have the same structure. For example, the electrical characteristics such as the withstand voltage with respect to the power supply voltage of the switching element, the temperature characteristics of the switching element, and the variation of Vth that is the threshold voltage (threshold value) of the switching element are substantially the same. Furthermore, when semiconductor elements have substantially the same electrical characteristics in one semiconductor integrated circuit, it is easy to consider the design margin and the design can minimize the operation margin, so that high efficiency and cost reduction are possible. Can be achieved.

  For this reason, it is difficult to change the design rules and device structure of a specific semiconductor element within a semiconductor integrated circuit. However, the maximum use of all switching elements within the semiconductor integrated circuit applied from an external power supply is difficult. When designing with design rules corresponding to voltage, the size of the switching elements built into the semiconductor integrated circuit becomes large. Therefore, it is unavoidable to change the design rules and device structure only for specific semiconductor elements in the semiconductor integrated circuit. Is adopted.

Incidentally, it is generally known that a semiconductor element constituting a semiconductor integrated circuit can operate at a high speed if its drive voltage is high. For example, it is preferable to operate the operation clock generation circuit and the arithmetic circuit at a high speed. On the other hand, for example, a crystal oscillation circuit or a frequency divider circuit operating at 32 KHz does not need to be operated at a very high speed.
In other words, semiconductor integrated circuits include a circuit that requires high speed operation by applying a high driving voltage and a circuit that requires low power consumption by applying a low driving voltage. is there.

  For example, when the maximum voltage of the external power supply is 5.5 V and the output voltage of the internal voltage down converter is 0.8 V, a switching element that constitutes an internal circuit that is directly driven by the external power supply voltage and driven by that voltage, The switching elements constituting the step-down circuit are designed with a design rule or device structure having a breakdown voltage of about 7.0V. On the other hand, the output voltage of the internal step-down circuit is applied, and the internal circuit driven by that voltage is designed with a design rule or device structure having a breakdown voltage of about 1.8V. The difference between the maximum voltage applied to the switching element and the design voltage, for example, between 5.5V and 7.0V is the operating margin.

  However, in this way, the design rule or device structure of the switching element constituting the internal step-down circuit using the external power supply voltage as the drive voltage and the switching element of the internal circuit using the internal step-down voltage output from the internal step-down circuit as the drive voltage For example, the following occurs with respect to Vth of the switching element.

  That is, if a switching element that can withstand a high voltage and a switching element that operates at a low driving voltage are configured in the same semiconductor integrated circuit, the electrical characteristics may vary due to differences in the semiconductor element structure.

The switching element will be described in detail as a MOS transistor. In the MOS transistor, the Vth changes according to the film thickness of the gate insulating film under the gate electrode and the impurity concentration of the diffusion layer constituting the channel, source electrode, and drain electrode.
However, the gate insulating film of a MOS transistor having a structure capable of withstanding a high voltage needs to be thick so that it is difficult to break down due to the high voltage, but the gate insulating film of a MOS transistor operating at a low driving voltage is thin. May be.
In other words, even if the thickness of the gate insulating film, which is one of the factors that determine Vth, is different, both Vths must be aligned with elements that are not gate insulating films. In this case, the manufacturing process is repeated many times. It is necessary to divide.

However, every time such a complicated manufacturing process elapses, subtle changes in the film thickness and impurity concentration in each manufacturing process accumulate, which causes manufacturing variations. Such manufacturing variation appears as a change in Vth.
If Vth is different between both MOS transistors, a leak current is generated between a MOS transistor having a structure capable of withstanding a high voltage and a MOS transistor operating at a low driving voltage. This leakage current further increases in accordance with variations in Vth of both MOS transistors, resulting in a problem that the current consumption of the semiconductor integrated circuit further increases.

  In order to prevent such a problem from occurring, it is only necessary to increase an operation margin between a MOS transistor having a structure capable of withstanding a high voltage and a MOS transistor operating at a low driving voltage. That is, a design rule or device structure that takes into account the operating margin is used.

The design rule is the definition of the dimensions of each element constituting the semiconductor element, and the device structure is the shape and structure of the semiconductor element itself.
The operation margin is the difference between the power supply voltage applied to the circuit and the lowest power supply voltage at which the circuit operates normally.

  However, if such an operation margin is increased, it becomes difficult to reduce the power consumption of a circuit composed of MOS transistors that operate at a low drive voltage.

  The electronic circuit of the present invention has been made in view of the above problems, and is normal without increasing the operating margin between a switching element having a structure capable of withstanding a high voltage and a switching element operating at a low driving voltage. It is an object of the present invention to provide an electronic circuit that can be operated in a simple manner.

  In order to solve the above-described problems, an electronic circuit of the present invention has the following structure.

A first internal circuit operating with an external power supply voltage;
An internal step-down circuit that inputs an external power supply voltage and generates a lower voltage output than that voltage;
In an electronic circuit having a second internal circuit operating at a low voltage output,
The internal step-down circuit has a reference voltage generation circuit, a differential amplifier circuit, and an internal step-down voltage output circuit,
The switching element that constitutes the reference voltage generation circuit and the differential amplifier circuit, and the constant current switching element and the current supply switching element that constitute the internal step-down voltage output circuit are substantially the same as the switching element that constitutes the first internal circuit. Have the same electrical characteristics,
The output switching element that determines the output voltage value of the internal step-down voltage output circuit has substantially the same electrical characteristics as the switching element constituting the second internal circuit,
The switching element constituting the first internal circuit and the switching element constituting the second internal circuit have different electrical characteristics.

  The switching element is a MOS transistor.

  The electrical characteristic is characterized by the value of the threshold voltage of the switching element or the temperature dependence of the threshold voltage.

  In the electronic circuit according to the present invention, the circuit driven by the external power supply voltage includes a switching element with a design rule or device structure that matches the maximum voltage of the external power supply voltage, and the circuit driven by the internal step-down voltage The switching element is configured with a design rule or device structure that matches the voltage, and the output switching element that determines the output voltage value of the voltage output circuit that constitutes the internal step-down circuit is driven by the internal step-down circuit. By making it substantially the same as the electrical characteristics, it is possible to set the operation margin of the output voltage value of the internal step-down voltage to the minimum, and it is possible to realize low power consumption.

[Overall description: Fig. 1]
Embodiments of a semiconductor integrated circuit according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an electronic circuit of the present invention. In FIG. 1, 100 is an electronic circuit, 101 is a reference power supply voltage terminal, 102 is an external power supply terminal for inputting an external power supply voltage, 103 is a first internal circuit, 104 is an internal step-down circuit, 105 is a reference voltage generation circuit, 106 Is a differential amplifier circuit, 107 is a constant current switching element, 108 is an output switching element, 109 is a current supply switching element, 110 is a second internal circuit, and 111 is an output voltage terminal of the internal step-down circuit 104.
A reference potential VDD is input to the reference power supply terminal 101, and an external power supply voltage VSS is input to the external power supply terminal 102. The output voltage VREG of the internal voltage down converter 104 is output from the output voltage terminal 104.

The electronic circuit 100 includes a first internal circuit 103 that is driven by a reference potential VDD supplied from a reference power supply terminal 101 and an external power supply voltage VSS supplied from an external power supply terminal 102, and steps down the voltage from the external power supply voltage VSS. An internal step-down circuit 104 that generates an output voltage VREG at the output voltage terminal 111, and a second internal circuit 11 that is driven by the reference potential VDD and the output voltage VREG.
0.

  The internal voltage down converter 104 includes a reference voltage generation circuit 105, a differential amplifier circuit 106, a constant current switching element 107, an output switching element 108, and a current supply switching element 109.

The switching elements constituting the first internal circuit 103, the reference voltage generation circuit 105, and the differential amplifier circuit 106, the constant current switching element 107, and the current supply switching element 109 have the same temperature characteristics and electrical characteristics. ing.
Further, the output switching element 108 and the switching elements constituting the second internal circuit 110 have the same temperature characteristics and electrical characteristics.

  The temperature characteristics and electrical characteristics of the switching element are determined by the design rules and device structure when manufacturing the semiconductor element. When these are made the same, the electrical characteristics of the switching elements formed of semiconductor elements are also the same.

The output switching element 108 determines the temperature characteristics and electrical characteristics of the output voltage VREG of the internal step-down circuit 104. Further, when the Vth of the output switching element 108 changes, the value of the output voltage VREG also changes.
However, by making the design rule and device structure of the switching elements constituting the second internal circuit 110 driven by the output voltage VREG the same, the temperature characteristics and electrical characteristics are also the same.
As a result, even if the output voltage VREG of the internal step-down circuit 104 changes due to a change in temperature or a variation in Vth of the output switching element 108, the switching elements constituting the output switching element 108 and the second internal circuit 110 Since the temperature characteristics and the electrical characteristics are the same, the operation margin of the second internal circuit 110 can be reduced. That is, the voltage set value of the output voltage VREG can be reduced, and the current consumed by the second internal circuit 110 can be set to the minimum.

This is a characteristic part of the electronic circuit of the present invention. That is, the switching element that determines the Vth, temperature characteristics, and electrical characteristics in the circuit that generates the drive voltage and the switching element in the circuit that operates at the drive voltage have the same Vth, temperature characteristics, and electrical characteristics. .
By doing so, it is not necessary to increase the operation margin when the electrical characteristics of the voltage generating side and the side driven by the voltage are different as in the prior art.

[Description of internal step-down circuit: Fig. 2]
Next, the configuration of the internal step-down circuit 104 will be described with reference to FIG. In FIG. 2, the internal step-down circuit 104 is described by taking a regulator circuit as an example. In FIG. 2, 203 is an internal step-down output circuit, and 211 is a reference resistor. Reference numerals 212, 213, 217, 218, 219, and 222 are P-channel MOS transistors. Reference numerals 214, 215, 220, 221, and 223 are N-channel MOS transistors. Reference numeral 216 denotes a reference voltage output terminal. The same numbers are assigned to the same configurations already described.

  The internal step-down output circuit 203 includes a constant current switching element 107, an output switching element 108, and a current supply switching element 109. The constant current switching element 107 is composed of a P-channel MOS transistor, and the output switching element 108 and the current supply switching element 109 are composed of N-channel MOS transistors.

The reference voltage generation circuit 105 is a circuit that generates a reference voltage.
The P-channel MOS transistor 212 has a source terminal connected to the reference power supply voltage terminal 101 via the reference resistor 211, and a drain terminal connected to the drain terminal of the N-channel MOS transistor 214. The source terminal of the N-channel MOS transistor 214 is connected to the external power supply terminal 102. This is called a first circuit row.
Similarly, the P-channel MOS transistor 213 has a source terminal connected to the reference power supply voltage terminal 101 and a drain terminal connected to the drain terminal of the N-channel MOS transistor 215. The source terminal of the N-channel MOS transistor 215 is connected to the external power supply terminal 102. This is called a second circuit row.

The gate terminals of the opposing P-channel MOS transistors are connected to each other and connected to the drain of the P-channel MOS transistor 213. The gate terminals of the opposing N-channel MOS transistors are connected to each other and are connected to the drain of the N-channel MOS transistor 214.
The electric characteristics of the reference resistor 211 and each MOS transistor are determined so that the flowing current is the same between the first circuit row and the second circuit row, and the reference voltage generation circuit 105 is a so-called current mirror circuit. It has become. The voltage output of this circuit is output from the reference voltage output terminal 216.

The differential amplifier circuit 106 is a circuit that performs differential amplification.
A P-channel MOS transistor 218 and an N-channel MOS transistor 220 are connected in series to form a third column, and a P-channel MOS transistor 219 and an N-channel MOS transistor 221 are connected in series to the fourth column. As a column. These and a P-channel MOS transistor 217 are connected in series between the reference power supply voltage terminal 101 and the external power supply terminal 102.

The gate terminals of the opposing N channel MOS transistors are connected to each other, and are connected to the drain of the N channel MOS transistor 221.
The gate terminals of the P-channel MOS transistors 217 and 218 are connected to the reference voltage output terminal 216, and the reference voltage of the reference voltage generation circuit 105 is input thereto.

  The P-channel MOS transistor 217 is a MOS transistor that performs constant current operation. The third column and the fourth column are the third column of the P-channel MOS transistor 218 and the N-channel MOS transistor 220. The electric characteristics of each MOS transistor are determined so that the flowing currents are the same, and the differential amplifier circuit 106 is also a so-called current mirror circuit.

The internal step-down output circuit 203 is a circuit that adjusts the output voltage of the differential amplifier circuit 106.
Between the reference power supply voltage terminal 101 and the external power supply terminal 102, a constant current switching element 107 of a P-channel MOS transistor, an output switching element 108 of an N-channel MOS transistor, and a current supply switching element of an N-channel MOS transistor 109 are connected in series.
The gate terminal of the constant current switching element 107 is connected to the reference voltage output terminal 216, and the reference voltage of the reference voltage generation circuit 105 is input thereto.
The gate terminal and the drain terminal of the output switching element 108 are connected to the gate terminal of the P-channel MOS transistor 219.
The gate terminal of the current supply switching element 109 is connected to the connection point between the P-channel MOS transistor 218 and the N-channel MOS transistor 220.

The connection point between the output switching element 108 of the N-channel MOS transistor and the current supply switching element 109 of the N-channel MOS transistor is the internal step-down circuit 104.
Output voltage terminal 111.

[Description of operation]
Next, the operation of the internal voltage down converter 104 will be described with reference to FIG. The operation of the internal voltage down converter 104 shown in FIG. 2 is the operation of a general regulator circuit.
The output voltage from the reference voltage output terminal 216 generated by the reference voltage generation circuit 105 is a P-channel MOS transistor which is a P-channel MOS transistor 217 of the differential amplifier circuit 106 and a constant current switching element 107 of the internal step-down output circuit 203. A bias voltage for generating a constant current bias is generated. This bias voltage is a voltage for completely turning on these P-channel MOS transistors, and thus the power consumption of these P-channel MOS transistors can be reduced.
For example, when Vth of a P-channel MOS transistor is about −0.5 V, the voltage is about −0.55 V, which is slightly higher than Vth in which the P-channel MOS transistor becomes a saturation region.

  The voltage is also input to the gate terminal of a P-channel MOS transistor 218 that is one input of the differential amplifier circuit 106. When the output voltage VREG fluctuates due to the operation of the second internal circuit 110 using the output voltage VREG output to the output voltage terminal 111 of the internal step-down circuit 104 as a power supply voltage, the internal voltage that is the other input of the differential amplifier circuit 106 Although the gate potential of the P-channel MOS transistor, which is the output switching element 108 that determines the output voltage value of the step-down output circuit 203, fluctuates, the differential amplifier circuit 106 is configured so that each input voltage is the same. The gate terminal of the N-channel MOS transistor, which is the current supply switching element 109 of the step-down output circuit 203, is feedback controlled to keep the output voltage VREG constant.

[Description of each element structure]
In FIG. 2, for example, a reference potential VDD of 0 V, an external power supply voltage VSS of −5.0 V is applied, a reference voltage output from the reference voltage output terminal 216 is −0.55 V, and an output voltage VREG is −1. A case where .05V is output will be described as an example.
In this example, each element is configured using either a design rule or device structure that can withstand a voltage of 5.5V and a design rule or device structure that can withstand a voltage of 1.5V.

  Since −3.95 V is applied between the source terminal and the drain terminal of the N-channel MOS transistor which is the current supply switching element 109 of the internal step-down output circuit 203, this switching element is approximately 5.5V. A design rule or device structure that can withstand voltage may be used.

  The drain terminal of the N-channel MOS transistor 220 of the differential amplifier circuit 106 is temporarily pulled to the reference potential VDD by the load fluctuation of the output voltage VREG and becomes a potential close to 0V. Since −5.0 V is applied to the source terminal side, a voltage close to −5.0 V is applied between the source terminal and the drain terminal of the N-channel MOS transistor 220, so that the voltage is approximately 5.5 V. Must be a design rule or device structure to withstand.

  In addition, since the N-channel MOS transistor 221 forms a current mirror circuit with the N-channel MOS transistor 220, it must have the same design rule or device structure as the N-channel MOS transistor 220.

Similarly, since the reference voltage output from the reference voltage output terminal 216 of the reference voltage generation circuit 105 is −0.55 V, a potential difference of 4.45 V is present between the source terminal and the drain terminal of the N-channel MOS transistor 215. Therefore, the MOS transistor may have a design rule or a device structure that can withstand a voltage of approximately 5.5V.

Since the N-channel MOS transistors 215 and 214 form a current mirror circuit,
In order to prevent the operating characteristics of the current mirror from deteriorating, the same design rule or device structure may be used.

  The potential of the drain terminal of the P-channel MOS transistor 212 of the reference voltage generation circuit 105 is connected to the gate terminal and the drain terminal of the N-channel MOS transistor 214. Since the potential of this portion rises from the external power supply voltage VSS by Vth of the N-channel MOS transistor 214, if the external power supply voltage VSS is −5.0V and the Vth of the N-channel MOS transistor 214 is 0.5V, P Since the drain voltage of the channel MOS transistor 212 is −4.5 V and a potential difference of 4.5 V is applied between the source terminal and the drain terminal, this MOS transistor is designed to withstand a voltage of approximately 5.5 V or A device structure may be used.

  Since the reference voltage output from the reference voltage output terminal 216 of the reference voltage generation circuit 105 is −0.55 V, the P-channel MOS transistor 213 of the reference voltage generation circuit 105 is −− between the source terminal and the drain terminal. Only 0.55V is applied. However, since the P-channel MOS transistor 213 forms a current mirror circuit with the P-channel MOS transistor 212, the same design rule or device structure is used in order to prevent the operating characteristics of the current mirror from being deteriorated. The design rule or device structure shall withstand a voltage of 5.5V.

  The P-channel MOS transistor 217 of the differential amplifier circuit 106 and the constant current switch element 107 of the internal step-down output circuit 203 are both P-channel MOS transistors that operate at a constant current. Even if the design rule or device structure withstands either 5.5 V or 1.5 V, the P channel MOS transistors 212 and 213 of the reference voltage generation circuit 105 have 5.5 V. Because of the design rule or device structure that can withstand voltage, the P-channel MOS transistor 217 and the P-channel MOS transistor 204 are arranged close to each other as semiconductor elements if the design rule or device structure can withstand a voltage of 5.5V. The area of the semiconductor integrated circuit constituting the semiconductor element is not pressed.

  Similarly, since only a voltage of about −0.55V is applied to the P-channel MOS transistors 218 and 219 of the differential amplifier circuit 106, a design rule that can withstand a voltage of 5.5V or 1.5V or Although a device structure may be used, P-channel MOS transistors can be arranged close to each other by using a design rule or device structure that can withstand a voltage of 5.5V.

[Explanation of electrical and temperature characteristics]
By the way, the output voltage VREG, which is the output voltage of the internal voltage down converter 104, is connected to the gate terminal and drain terminal of an N-channel MOS transistor that is an output switching element 108 that determines the output value of the internal voltage down converter 104. The voltage value is obtained by adding Vth of the N-channel MOS transistor as the output switching element 108 to the potential of the portion connected to the gate terminal of the P-channel MOS transistor 219 as one input of the dynamic amplifier circuit 106.

The gate voltage of the P-channel MOS transistor 219 is the gate voltage of the P-channel MOS transistor 218 which is the other input, that is, the voltage (−0.55 V) of the reference voltage output terminal 216 of the reference voltage generation circuit 105. Will be the same.
If Vth of the N-channel MOS transistor that is the output switching element 108 that determines the output voltage value of the internal voltage down converter 104 is 0.5 V, the output voltage VREG of the internal voltage down converter 104 is equal to the gate of the P channel MOS transistor 219. A value obtained by adding Vth 0.5 V of the N-channel MOS transistor as the output switching element 108 to the voltage −0.55 V is −1.05 V.

That is, the change in the output voltage characteristic of the internal voltage down converter 104 is determined by the change in Vth of the N-channel MOS transistor that is the output switching element 108.
The temperature characteristic of the output voltage VREG of the internal voltage down converter 104 is determined by the temperature characteristic (temperature dependence) of Vth of the N-channel MOS transistor that is the output switching element 108.

  Even when the Vth of the N-channel MOS transistor serving as the output switching element 108 increases and the potential difference between the reference potential VDD and the output voltage VREG increases, the second internal circuit 110 driven by the output voltage VREG is configured. The Vth of the P-channel MOS transistor 222 and the N-channel MOS transistor 223 to be increased also increases, and as a result, the internal impedance of these transistors increases, so that the current consumption of the second internal circuit 110 does not increase.

  Further, even if the Vth of the N-channel MOS transistor which is the output switching element 108 becomes low and the potential difference between the reference potential VDD and the output voltage VREG becomes small, the P-channel MOS transistor 222 and the N-channel MOS transistor The Vth of 223 is also lowered, and as a result, these transistors can be operated with a low driving voltage.

  The same applies to the case where the temperature is increased and Vth is decreased, and the case where the temperature is decreased and Vth is increased.

As is apparent from the above description, the electronic circuit of the present invention is driven by the first internal circuit 103 driven by the external power supply voltage VSS, the internal voltage down converter 104, and the output voltage VREG stepped down by the internal voltage down converter 104. And a second internal circuit 110.
By making the design rule or device structure of the switching element for output 108 that determines the output voltage value of the internal step-down circuit 104 the same as the design rule or device structure of the switching element that constitutes the second internal circuit 110, Even if the Vth of the switching element 108 fluctuates and the output voltage VREG fluctuates, an increase in current consumption of the second internal circuit 110 can be suppressed and an operating voltage range can be secured.

  The electronic circuit of the present invention can be applied to a system driven by an external power supply voltage such as a secondary battery. In particular, it is suitable for a system that requires a long operation time, such as a portable electronic device.

It is a block diagram explaining the electronic circuit of this invention. It is a circuit diagram explaining the internal step-down circuit of the electronic circuit of the present invention. It is a block diagram explaining the prior art shown in patent document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Electronic circuit 101 Reference power supply voltage terminal 102 External power supply terminal for external power supply voltage input 103 First internal circuit 104 Internal voltage down converter 105 Reference voltage generation circuit 106 Differential amplifier circuit 107 Constant current switching element 108 Output switching element 109 Current Supply switching element 101 Reference power supply terminal 102 External power supply terminal 110 Second internal circuit 111 Output voltage terminal of internal step-down circuit 104

Claims (3)

A first internal circuit operating with an external power supply voltage;
An internal step-down circuit that inputs the external power supply voltage and generates a lower voltage output than the voltage;
An electronic circuit having a second internal circuit operating at the low voltage output;
The internal voltage down converter includes a reference voltage generation circuit, a differential amplifier circuit, and an internal voltage down output circuit.
The switching element constituting the reference voltage generation circuit and the differential amplifier circuit, the constant current switching element and the current supply switching element constituting the internal step-down voltage output circuit constitute the first internal circuit. It has almost the same electrical characteristics as the switching element,
The output switching element that determines the output voltage value of the internal step-down voltage output circuit has substantially the same electrical characteristics as the switching element that constitutes the second internal circuit,
An electronic circuit, wherein the switching element constituting the first internal circuit and the switching element constituting the second internal circuit have different electrical characteristics.   The electronic circuit according to claim 1, wherein the switching element is a MOS transistor.   The electronic circuit according to claim 1, wherein the electrical characteristic is a threshold voltage value of the switching element or a temperature dependency of the threshold voltage.

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