JP3258869B2 - Static electricity protection circuit for integrated circuits - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit configuration for protecting an integrated circuit such as an IC from static electricity.

[0002]

2. Description of the Related Art The integration density of integrated circuits such as ICs has increased due to the progress of microfabrication technology. On the other hand, I
Various elements inside C are miniaturized, and resistance to static electricity is low. Therefore, conventionally, an electrostatic protection circuit has been provided in an integrated circuit for the purpose of preventing destruction of elements in the integrated circuit due to static electricity.

The configuration of an integrated circuit having a conventional electrostatic protection circuit will be described below with reference to FIG.

In FIG. 7, terminals T1 to T4 correspond to pins when an integrated circuit is packaged,
The terminal T1 is connected to the high voltage power supply line 12 during the operation of the integrated circuit.
Is a terminal for supplying power from the power supply VCC on the high potential side to the power supply. The terminal T2 is a terminal for connecting the low-voltage power supply line 14 to a power supply on the low potential side, here, a ground power supply GND. The terminal T3 is a terminal for inputting and outputting a signal to and from the signal processing circuit [1] 10, for example.
Reference numeral 4 denotes a terminal for inputting / outputting a signal to / from the signal processing circuit [3] 10, for example.

In order to protect the internal circuit from static electricity that enters the integrated circuit through the terminals T1 to T4,
Protection diodes D1, D2 and protection resistors R1-n, RI
An O-static protection circuit is provided.

The protection resistors R 1... N are provided between the signal processing circuit 10 and / or one or both of the high-voltage power line 12 and the low-voltage power line 14. The protection resistor RIO is connected to the circuit 10.

The protection diode D1 is connected to terminals T3 and T3.
It is provided between T4 and the power supply line 12 in a direction in which current flows from the terminals T3 and T4 toward the power supply line 12, respectively, and between the terminals T3 and T4 and the low-voltage power supply line 14,
A protection diode D2 for flowing a current from the low-voltage power supply line 14 to the terminals T3 and T4 is provided.

[0008]

From the viewpoint of protecting each signal processing circuit 10 from static electricity, it is preferable to increase the resistance values of the protection resistors R1 to n and RIO. This is because a large resistance can prevent a large current due to static electricity from flowing through each signal processing circuit 10. Further, in an integrated circuit, these protection resistors R1 to n and RIO are often constituted by diffusion resistors. If the resistance value is increased, that is, if the area is increased, static electricity can be easily released from the diffusion resistors into the substrate. Because.

However, the protection resistors R1-n, RIO
When the resistance value of the signal processing circuit 10 is increased, the output impedance of the signal processing circuit 10 increases, and the circuit characteristics may be degraded, such as the signal processing speed of each circuit being reduced. Therefore, there is a problem that these protection resistances cannot be increased so much that destruction of the element due to static electricity cannot be reliably prevented.

Further, a protection resistor corresponding to the circuit scale of each signal processing circuit 10 must be individually provided.
There is also a problem that the area and power consumption of the integrated circuit increase.

Further, in the configuration of the conventional electrostatic protection circuit, as shown as Case 1 in FIG. 7, when the integrated circuit is not operating, for example, a negative charge is applied to the terminal T1 and a positive charge is applied to the terminal T3. In this case, the protection diode D1 is turned on, and a current flows in a path from the terminal T3 to the power supply line 12, so that static electricity is discharged. However, when a positive charge is applied to the terminal T3 and a negative charge is applied to the terminal T2 as in Case 2, the diode D2 does not operate, and
Since no discharge path is formed in the integrated circuit, the static electricity is not discharged. As described above, in the conventional configuration, an appropriate discharge path cannot be formed inside the integrated circuit depending on the state of the generated static electricity, and improvement has been demanded.

An object of the present invention is to provide an electrostatic protection circuit for reliably protecting an integrated circuit from static electricity without affecting the operation of the integrated circuit.

[0013]

To achieve the above object, according to the solution to ## by the electrostatic protection circuit of the integrated circuit of the present invention, first, group
As a basic configuration, a high-voltage power supply line to which a power supply on the high potential side is connected, and both or any one of the input terminal and the output terminal are provided, and both or any one of these terminals is provided. A first protection element for flowing only a current flowing to the high-voltage power supply line, and a low-voltage power supply line connected to a low-potential-side power supply and an input / output terminal; A second protection element is provided between the high-voltage power supply line and the low-voltage power supply line, and a third protection element is provided between the high-voltage power supply line and the low-voltage power supply line to flow only a current flowing from the high-voltage power supply line to the low-voltage power supply line.

Further , when the third protection element generates a potential difference between the two power supply lines that is sufficiently larger than a potential difference generated between the high-voltage power supply line and the low-voltage power supply line during operation of the integrated circuit, for example. Then, a current is supplied from the high-voltage power line to the low-voltage power line.

[0015] Ri by such a configuration, during operation of the integrated circuit, the protection device without any operation, are prevented from excessive power consumption occurs a current flows between the power supply line during operation . Further, when static electricity enters the circuit from each terminal of the integrated circuit, the first or second protection element is provided.
By operating one or both of the third protection elements, static electricity is reliably discharged without flowing a current to a signal processing circuit or the like in the integrated circuit.

According to the present invention , in the case of an electrostatic protection circuit of an integrated circuit having a plurality of power supply lines, first, each power supply line, and / or one or both of an input terminal and an output terminal, The first and second protection elements are provided between them. Further, a backflow prevention element for preventing a current from flowing from one high-voltage power supply line to the other high-voltage power supply line is provided between the plurality of high-voltage power supply lines, and a third element for flowing only a current flowing from the high-voltage power supply line to the low-voltage power supply line is provided. The protection element is provided between the backflow prevention element and the plurality of low-voltage power supply lines.

The plurality of high-voltage power lines often have different voltages when the integrated circuit operates. In the present invention, by providing the high-voltage power supply line with the backflow prevention element, a current flows between the plurality of high-voltage power supply lines during the operation of the integrated circuit, thereby preventing the operation from being adversely affected.

On the other hand, due to static electricity generated between the terminals of the integrated circuit, for example, a potential difference between these high-voltage power lines and each low-voltage power line that is sufficiently large during operation of the integrated circuit is generated between these power lines. In this case, the backflow prevention element and the third protection element can flow a current from the high-voltage power supply line to the low-voltage power supply line. The third protection element can form an electrostatic discharge path between the high-voltage power supply line and the low-voltage power supply line via the backflow prevention element by providing one power supply line in one integrated circuit even if a plurality of power supply lines are provided. Therefore, the influence on the area of the integrated circuit and the like is small.

Further, the first protection element and the second protection element can be constituted by at least one diode, and the third protection element is a transistor, a Zener diode, a thyristor or a plurality of diodes connected in series. It can be constituted by either. And
These elements can be easily formed simultaneously with the formation of other elements to be made in the integrated circuit.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. Note that the same reference numerals are given to portions corresponding to the drawings described above, and description thereof will be omitted.

[ Basic Configuration ] (Overall Configuration) FIG. 1 shows a configuration of an electrostatic protection circuit according to a basic configuration of the present invention . In FIG. 1, between the terminals T3 and T4 and the high-voltage power line 12 and the low-voltage power line 14, protection diodes D1 and D2 are connected as first and second protection elements, respectively, as in the related art. . Further, a third line is provided between the high-voltage power line 12 and the low-voltage power line 14.
A protection diode 16 configured by connecting n diodes in series is provided as a protection element.

The protection diode D1 allows only a current flowing from the terminals T3 and T4 for inputting and outputting signals to and from the signal processing circuit 10 other than the power supply to the high-voltage power supply line 12, and the protection diode D2 has a low-voltage power supply (for example, ground). (Power supply) Only a current flowing from the line 14 to the terminals T3 and T4 flows. Accordingly, the protection diodes D1 and D2 are connected to the high-voltage power supply and the low-voltage power supply, respectively, to the power supply lines 12 and 14, respectively. When the integrated circuit is in an operable state, a voltage is applied in the reverse direction. Does not affect operation.

On the other hand, when a predetermined power supply is connected to the power supply lines 12 and 14 of the integrated circuit and a potential difference (VCC-VEE) occurs, a voltage is applied to the protection diode 16 in the forward direction. However, this protection diode 16
Is set such that the number n of diodes does not operate unless the potential difference is sufficiently larger than the potential difference (VCC-VEE). For example, if (VCC-VEE) is set to about 5V, the operating voltage of the protection diode 16 is set to about 7V. Here, assuming that the ON voltage of each diode constituting the protection diode 16 is about 0.6 V, the number n of diodes connected in series is about 14 to 16.

Therefore, when the integrated circuit is operating normally, the protection diode 16 does not operate and the high voltage power supply line 1
No current flows from 2 to the low-voltage power supply line 14. Therefore, unnecessary power consumption is prevented.

On the other hand, the potential difference caused by static electricity is
Generally, the potential difference between the power supply lines 12 and 14 during operation is extremely large (for example, several hundred volts). Accordingly, when the integrated circuit is not operating, for example, before the integrated circuit is mounted on a printed circuit board, and the power supply line is in an electrically floating state, the power supply line 12,
When a large potential difference occurs in the power supply line 14, the protection diode 16 operates in response to this, and a current flows from the high-voltage power supply line 12 to the low-voltage power supply line 14.

(Electrostatic Discharge Path) Next, an electrostatic discharge path will be described with reference to FIGS.

(1) Case 1 As shown in FIG. 2A, when a negative charge is applied to the terminal T1 and a positive charge is applied to the terminal T3 as static electricity, the protection diode D1 is turned on. Then, a current flows in a path from the terminal T3 to the high-voltage power supply line 12, and static electricity is discharged.

(2) Case 2 As shown in FIG. 2B, the terminal T3 has a positive charge and the terminal T
When a negative charge is applied to the protection diode 2, the protection diode D2 does not operate because a reverse voltage is applied to the protection diode D2. But,
Since the protection diode D1 and the protection diode 16 are connected in series in the forward direction between the terminal T3 and the low-voltage power supply line 14, when the protection diodes D1 and 16 are turned on, as shown by a dotted line in the figure. Discharge path is formed, and static electricity is discharged.

(3) Case 3 As shown in FIG. 2C, when a negative charge is applied to the terminal T3 and a positive charge is applied to the terminal T2, the protection diode D2 is turned on, and the low voltage is applied. Power supply line 14 to terminal T
Current flows in the path toward No. 3 and static electricity is discharged.

(4) Case 4 As shown in FIG. 2D, the terminal T1 has a positive charge and the terminal T
When a negative charge is given to 3, the protection diode D1 does not operate. On the other hand, between the terminal T1 and the terminal T3, the protection diode 16 and the protection diode D2 are connected in series in the forward direction. Therefore, the protection diodes 16 and D2 are turned on, a discharge path shown by a dotted line is formed, and static electricity is discharged.

(5) Case 5 As shown in FIG. 3, when a positive charge is applied to the terminal T3 and a negative charge is applied to the terminal T4, the protection diode D1 is connected between the terminal T3 and the terminal T4. The diode 16 and the protection diode D2 'are connected in series. Therefore, these protection diodes are turned on, a discharge path as shown by a dotted line is formed, and static electricity is discharged.

(6) Case 6 Contrary to Case 5, a negative charge is applied to the terminal T3 and a terminal T4
Are supplied with a positive charge, the terminals T4 and T3
Between the protection diode D1 'and the protection diode 16,
The protection diode D2 is connected in series. Also in this case, these protection diodes are turned on, a discharge path is formed as shown by a dashed line in FIG. 3, and static electricity is discharged.

In the conventional static electricity protection circuit, when static electricity is applied to each of the terminals T1 to T4 in the state shown in the case 2, the case 4, the case 5, and the case 6, between the power supply lines 12 and 14, Since no discharge path was formed, it could not be discharged. On the other hand, in the present embodiment, the high-voltage power line 12
In this case, static electricity can be reliably discharged by providing the protection diode 16 that allows a current to flow only toward.

In the configuration described above, a third power supply line provided between the high-voltage power supply line 12 and the low-voltage power supply line 14 is provided.
The protection element is not limited to the protection diode 16 and is shown in FIG.
It is also possible to use a Zener diode 30 as shown in FIG. As with the protection diode 16, the Zener diode 30 allows a current to flow from the high-voltage power line 12 to the low-voltage power line 14 when a potential difference that is sufficiently larger than the potential difference during the operation of the integrated circuit occurs between the power lines 12 and 14. The breakdown voltage is set as follows.

Further, as the third protection element, a protection transistor 32 composed of n PNP transistors as shown in FIG. 5 can be used. Protection transistor 3
2, the collectors of the n transistors Q1 to n are connected to the low-voltage power supply line 14, respectively. The transistor Q whose emitter is connected to the high-voltage power supply line 12
The base of the transistor Q2 is connected to the emitter of the transistor Q2, and the base of the transistor Q2 is connected to the emitter of the transistor Q3. As described above, the emitter of the low-voltage transistor is connected to the base of the high-voltage transistor, and the base of the transistor Qn on the lowest voltage is connected to the low-voltage power supply line 14.

The protection transistor 32 has a potential difference of n × V between the high-voltage power line 12 and the low-voltage power line 14.
When the voltage exceeds BE, the transistor Q1 turns on.
A current can flow from the high-voltage power line 12 to the low-voltage power line 14. Therefore, like the protection diode 16 of FIG. 1 and the Zener diode 30 of FIG. 4, the number n of transistors is such that the protection transistor 32 operates with a potential difference sufficiently larger than the potential difference between the power supply lines 12 and 14 during the operation of the integrated circuit. Should be set.

When an NPN transistor is used, the collectors of the transistors Q1 to Qn are connected to the high-voltage power supply line 12, and the base of the transistor Q1 is connected to the high-voltage power supply line 12.
By connecting the base of the low-voltage transistor to the emitter of the high-voltage transistor in the same manner, the above-described protection transistor can be configured.

As a protection element provided between the power supply lines 12 and 14, a thyristor can be applied. In this case, a plurality of thyristors are connected similarly to the protection transistor 32.

[0039] [Embodiment type Status] Next, the configuration of the electrostatic protection circuit of an integrated circuit having a plurality of power supply lines having different voltages according to the embodiment will be explained with reference to FIG.

In FIG. 6, the high voltage power supply lines 12, 22
Are connected to high-voltage power supplies of different voltages via terminals T1 and T11, respectively, and supply power from the high-voltage power supplies to the signal processing circuits 10 and 20, respectively. Similarly, the low-voltage power supply lines 14 and 24 are connected to low-voltage power supplies of different voltages via terminals 2 and T12. Terminals T3 and T13 are terminals for inputting and outputting signals other than power to the signal processing circuits 10 and 20, respectively.
As in the first embodiment, a protection diode D1 is provided between the power supply line 13 and the high-voltage power supply lines 12 and 22, and between the terminals T3 and T13 and the low-voltage power supply lines 14 and 24, respectively.
Similarly, protection diodes D2 are provided.

Diodes D10 and D11 are provided between the high-voltage power lines 12 and 22 as backflow preventing elements for preventing a current from flowing between the two power lines. Specifically, each of the diodes D10, D11
Are connected to the high-voltage power supply lines 12 and 22, respectively, and the cathode sides are connected to each other. For example, when the voltage of the high voltage power line 12 is higher than the power of the high voltage power line 22 during the operation of the integrated circuit, a forward voltage is applied to the diode D10, but a reverse voltage is applied to the diode D11. Is done. Therefore, the diode D11 prevents a current from flowing from the high voltage power line 12 to the high voltage power line 22.
Conversely, when the voltage of the high-voltage power supply line 22 is higher than the voltage of the high-voltage power supply line 12, the diode D10
This prevents a current from flowing from the high voltage power line 22 to the high voltage power line 12.

On the other hand, diodes D20 and D21 are provided between the low-voltage power lines 14 and 24 as backflow prevention elements for preventing a current from flowing between the two low-voltage power lines during the operation of the integrated circuit. ing. The cathodes of the diodes D20 and D21 are connected to the low-voltage power supply lines 14 and 24, respectively, and the anodes are connected to each other.

Further, the backflow preventing elements D10 and D1 on the high pressure side
1 as a third protection element between the cathode of the first embodiment and the anodes of the backflow prevention elements D20 and D21 on the low pressure side.
Similarly to the protection diode 16, a protection diode 34 in which a plurality of diodes are connected in series is connected.

The high-pressure side backflow prevention elements D10, D1
1, protection diode 34 and low-voltage side backflow prevention element D2
The operating voltages 0 and D21 are set sufficiently higher than the maximum voltages generated between the high-voltage power lines 12, 22 and the low-voltage power lines 14, 24 during the operation of the integrated circuit. When a voltage equal to or higher than the set operating voltage is generated between any of the high-voltage power supply lines 12 and 22 and the low-voltage power supply lines 14 and 24 due to static electricity, as shown by a dotted line in FIG. As a discharge path, the high-voltage power lines 12, 22 (a, b) are connected to the low-voltage power lines 14, 2,
Current flows toward 4 (c, d).

Therefore, a static electricity discharge path is formed between the high-voltage power supply line and the low-voltage power supply line without causing a current to flow between the plurality of high-voltage power supply lines and between the low-voltage power supply lines during operation of the integrated circuit. And the static electricity is reliably discharged. For example, as illustrated in FIG. 6, when a positive charge is given to the terminal T11 and a negative charge is given to the terminal T3 as static electricity, the static electricity passes from the terminal T11 through bc, and furthermore, A discharge path from the low-voltage power supply line 14 to the terminal T3 through the diode D2 is formed.

It should be noted that the number of power supply lines having different voltages is not limited to two, and more power lines can be applied. In this case, if a backflow prevention element as shown in FIG. 6 is provided for each power supply line, the other configuration is the same as that of FIG. For example, when there are a plurality of high-voltage power supply lines, a diode whose anode side is connected to each high-voltage power supply line is provided as a backflow prevention element, similarly to the diodes D10 and D11. What is necessary is just to connect to a cathode. When there are a plurality of low-voltage power lines, a diode similar to the diodes D20 and D21 may be provided as a backflow prevention element corresponding to each low-voltage power line.
Even if there are a plurality of power supply lines having different voltages as described above, the protection diode 34 of FIG.
If they are available, they can be used in common.

The protection diode 34 can be replaced with a structure similar to that of the zener diode 30 or the protection transistor 32 as shown in FIGS. Further, the configuration is not limited thereto, and a plurality of thyristors may be connected.

As a protection element provided between the high-voltage power supply line and the low-voltage power supply line, a diode is generally the simplest in structure, and is therefore easy to manufacture. However, since other elements are also used in the signal processing circuit, they can be formed simultaneously with other elements of the integrated circuit without providing a special manufacturing process.

[0049]

According to the structure of the static electricity protection circuit for an integrated circuit of the present invention, various static electricity discharge paths can be formed in the integrated circuit without affecting the original operation of the integrated circuit. Therefore, it is possible to reliably protect the integrated circuit from static electricity.

[0050] Then, in the case where a different number plurality of power supply lines in voltage, regardless of the number or the signal processing circuit scale of such a signal processing circuit, between the high voltage power supply line and the low-voltage power line, in an integrated circuit By providing at least one third protection element, a discharge path from the high-voltage power line to the low-voltage power line can be formed. Therefore, the static electricity protection circuit can be configured with a small number of elements, which is extremely advantageous in miniaturization of an integrated circuit.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an electrostatic protection circuit having a basic configuration of the present invention.

FIG. 2 is a diagram illustrating a discharge path of the electrostatic protection circuit of FIG.

FIG. 3 is a diagram illustrating a discharge path different from FIG. 2;

FIG. 4 is a diagram showing another configuration example of FIG. 1;

FIG. 5 is a diagram showing another configuration example of FIG. 1;

6 is a diagram showing a structure of the electrostatic protection circuit according to type state of the present invention.

FIG. 7 is a diagram showing a configuration of a conventional electrostatic protection circuit.

[Description of Signs] 10,20 signal processing circuit, 12,22 high voltage power supply line, 14,24 low voltage power supply line, 16,34 protection diode, 30 zener diode, 32 protection transistor.

Claims (5)

(57) [Claims] 1. An electrostatic protection circuit for an integrated circuit having a plurality of power lines, provided between a plurality of high voltage power lines and a plurality of input terminals and / or an output terminal. A first protection element that allows only a current flowing from the terminal to the high-voltage power supply line; and a first protection element that is provided between the plurality of low-voltage power supply lines and the plurality of terminals, respectively, and only the current flowing from the low-voltage power supply line to the terminal is provided. A second protection element, which is provided between the plurality of high-voltage power supply lines, and prevents a current from flowing from one high-voltage power supply line to the other high-voltage power supply line; And a third protection element provided between the low-voltage power supply line and the low-voltage power supply line and flowing only a current flowing from the high-voltage power supply line to the low-voltage power supply line. Static electricity protection circuit. 2. The static electricity protection circuit for an integrated circuit according to claim 1 , further comprising a plurality of low-voltage power lines provided between said plurality of low-voltage power lines to prevent a current from flowing from one low-voltage power line to another low-voltage power line. A static electricity protection circuit for an integrated circuit, comprising: 3. A static electricity protection circuit of the integrated circuit according to claim 1 or claim 2, the electrostatic protection circuit of the integrated circuit, wherein the backflow prevention device is configured by a diode. 4. The electrostatic protection circuit of the integrated circuit according to any one of claims 1 to 3, wherein the first protection element and the second protection element is constituted by at least one diode An electrostatic protection circuit for an integrated circuit, comprising: 5. The electrostatic protection circuit of the integrated circuit according to any one of claims 1 to 4, wherein the third protection element, a transistor, either of the zener diode, a thyristor or a plurality of series-connected diodes And a static electricity protection circuit for an integrated circuit.