JP2008028214A - Electrostatic countermeasure circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic countermeasure circuit capable of suppressing a lowering of a transmission impedance. <P>SOLUTION: The electrostatic countermeasure circuit is equipped with: a signal line 11 having one end 11a and the other end 11b connected to an IC 12, electrostatic countermeasures 14 connected between this signal line 11 and the ground, and coils 15 serially connected with the signal line 11. A capacitance of the electrostatic countermeasures 14 is set to 0.3 pF or less. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a static electricity countermeasure circuit used for protecting various electronic devices from static electricity.

  A conventional static electricity countermeasure circuit of this type is provided between two signal lines 2 connected to an IC 1 and between the two signal lines 2 and a ground 3 as shown in FIGS. An electrostatic pulse generated when an electrostatic countermeasure component 4 such as a varistor or a Zener diode and a coil component 5 connected in series to the two signal lines 2 are brought into contact with a human body and a terminal of an electronic device. Is bypassed by the anti-static component 4 to suppress static electricity applied to the electric circuit such as the IC 1 inside the electronic device, thereby preventing the electric circuit from being destroyed by the static electricity.

  FIG. 14 is a voltage waveform diagram applied to the IC 1 when an electrostatic pulse of 8 kV is applied to the conventional static electricity countermeasure circuit. As is clear from FIG. 14, the peak voltage applied to the IC 1 is reduced to about 200V.

As prior art document information relating to the invention of this application, for example, Patent Document 1 is known.
JP 2005-223240 A

  In the above-described conventional static electricity countermeasure circuit, the capacitance of the varistors and Zener diodes constituting the static electricity prevention component 4 is large, so that the transmission signal flows to the ground 3 via the static electricity prevention component 4, thereby transmitting data. There has been a problem that impedance (TDR characteristics) is reduced.

  That is, as the transmission signal speeds up and the transmission rate is increased to the gigabit level, problems such as the generation of radiation noise and the signal waveform not being accurately transmitted due to the deformation of the signal waveform are increasing. In order to solve this problem, it is important to more strictly suppress reflection and loss of transmission signals.

  Particularly in the design of transmission lines, it is necessary to match the impedance of the transmission line with the impedance of the input / output circuit and IC in order to suppress the reflection and loss of the transmission signal. The end circuit is 50Ω, and the differential transmission circuit is 100Ω.

  For example, a high-speed differential transmission line such as DVI has a standard with a transmission impedance of 100 ± 15 Ω, and a transmission line with a transmission impedance outside this standard may not be able to transmit data.

  FIG. 15 shows the transmission impedance in a conventional static electricity countermeasure circuit. As is clear from FIG. 15, the transmission impedance is out of the standard, and data transmission cannot be performed.

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide an anti-static circuit capable of suppressing a reduction in transmission impedance.

  In order to achieve the above object, the present invention has the following configuration.

  According to a first aspect of the present invention, there is provided a signal line having one end and the other end connected to the IC, an anti-static component connected between the signal line and the ground, and the signal line. And a coil component connected in series, and the electrostatic countermeasure component has a capacitance of 0.3 pF or less. According to this configuration, since the electrostatic countermeasure component has a small capacitance, the transmission signal is static It does not flow to the ground via the countermeasure component, and this provides an effect that the transmission impedance can be suppressed from decreasing.

  The invention according to claim 2 of the present invention is particularly one in which the anti-static component is provided on one end side of the signal line with respect to the coil component. According to this configuration, from the one end portion of the signal line toward the IC, The intruding electrostatic pulse can be removed by anti-static components, and the static pulse that could not be removed is removed by the subsequent coil components functioning as a low-pass filter, so that more static electricity is applied to the IC. The effect of being able to be suppressed is obtained.

  The invention according to claim 3 of the present invention particularly includes an anti-static component having one insulating layer and a pair of electrodes provided on the same surface of the one insulating layer or on the front and back surfaces of the insulating layer facing each other. The voltage-dependent resistance material provided between the pair of electrodes, and according to this configuration, the electrostatic capacity of the anti-static component can be easily reduced to 0.3 pF or less. An effect is obtained.

  As described above, the antistatic circuit of the present invention includes a signal line having one end and the other end connected to the IC, an antistatic component connected between the signal line and the ground, and the signal line. And the coil component connected in series with each other, and the electrostatic capacitance of the anti-static component is 0.3 pF or less, the electrostatic capacitance of the anti-static component is small. Therefore, it is possible to prevent the transmission impedance from being lowered.

  FIG. 1 is a schematic diagram of an electrostatic countermeasure circuit according to an embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of the electrostatic countermeasure circuit.

  As shown in FIG. 1 and FIG. 2, the electrostatic protection circuit according to one embodiment of the present invention includes two signal lines 11 having one end 11a and the other end 11b connected to the IC 12, and the signal line. 11 and an antistatic component 14 connected between the ground 13 and a coil component 15 connected in series with the signal line 11, and the electrostatic capacitance of the antistatic component 14 is 0.3 pF or less. It is what.

  In the above configuration, each of the two signal lines 11 has one end portion 11a connected to another electric circuit (not shown) via a connector 16a, and the other end portion 11b connected to the IC 12 via a connector 16b. Connected.

  The static electricity countermeasure component 14 is composed of an ESD suppressor connected between each signal line 11 and the ground 13 and has a capacitance of 0.3 pF or less. Further, as shown in FIGS. 3 and 4, the antistatic component 14 includes one insulating layer 17, a pair of electrodes 18 a and 18 b provided on the same surface of the one insulating layer 17, and the pair of electrodes. The voltage-dependent resistance material 19 provided between the electrodes 18a and 18b is provided.

  If the electrostatic countermeasure component 14 is constructed using a plurality of pairs of electrodes provided in a plurality of insulating layers such as a varistor, the capacitance increases, but as shown in FIGS. 3 and 4 above. By adopting a simple structure, the capacitance can be easily reduced to 0.3 pF or less. Further, the pair of electrodes 18a and 18b may be provided on the front and back surfaces of the insulating layer 17 facing each other. However, if the structure shown in FIGS. 3 and 4 is employed, the pair of electrodes 18a and 18b are opposed to each other. Since the area can be reduced, the capacitance can be further reduced.

  The static electricity countermeasure component 14 has one electrode 18 a of the pair of electrodes 18 a and 18 b connected to the signal line 11 and the other electrode 18 b connected to the ground 13. The voltage-dependent resistance material 19 uses a material made of a metal powder containing at least one of aluminum, nickel, and copper and a resin containing at least one of silicon, epoxy, and phenol.

  The coil component 15 has inductance elements such as a common mode noise filter, a common mode choke, and an inductor connected in series with each signal line 11. In this case, common mode noise can be removed by using a common mode noise filter. A pair of electrodes in each inductance element of the coil component 15 is connected to the signal line 11.

  The impedance of the coil component 15 needs to be selected according to the capacitance of the anti-static component 14. For example, when the impedance of the transmission line is 50Ω, the impedance of the coil component 15 may be 50-60Ω. Also, by providing this coil component 15, the transmission impedance can be increased, and thus the transmission impedance (TDR characteristic) can be kept within the standard range.

  In the above-described embodiment of the present invention, the electrostatic capacity of the antistatic component 14 is as small as 0.3 pF or less, so that a transmission signal does not flow to the ground 13 via the antistatic component 14. As a result, it is possible to obtain an effect that the transmission impedance can be prevented from being lowered.

  FIG. 5 is a diagram showing transmission impedance in the static electricity countermeasure circuit according to the embodiment of the present invention.

  As is apparent from FIG. 5, the transmission impedance can be kept within the standard range without decreasing. This also prevents data transmission from being disabled.

  FIG. 6 is a diagram showing the relationship between capacitance and transmission impedance. In FIG. 6, A is an anti-static component having a capacitance of 0.1 pF, B of 0.3 pF, and C of 0.5 pF. 14 shows respective transmission impedances.

  As is apparent from FIG. 6, the transmission impedance can be kept within the standard range by setting the electrostatic capacity of the anti-static component 14 to 0.3 pF or less.

  Further, in the static electricity countermeasure circuit according to the embodiment of the present invention, as shown in FIG. 7, the peak voltage applied to the IC 12 when an 8 kV static pulse is applied can be greatly reduced.

  As shown in FIGS. 8 and 9, the antistatic component 14 is provided on the one end 11 a side of the signal line 11 with respect to the coil component 15, that is, on the front side where the electrostatic pulse enters toward the IC 12. Then, the electrostatic pulse that has entered from the one end 11a of the signal line 11 toward the IC 12 can be removed by the anti-static component 14, and the subsequent coil component 15 functions as a low-pass filter. Therefore, the static electricity applied to the IC 12 can be further suppressed.

  FIG. 10 shows a voltage waveform diagram applied to the IC 12 when an electrostatic pulse of 8 kV is applied in the static electricity countermeasure circuits shown in FIGS. 8 and 9, and as is apparent from FIG. The peak voltage applied to is greatly reduced to about 60V. Also, as shown in FIG. 11, the transmission impedance can be kept within the standard range. In addition, even if the transmission impedance is lowered due to the electrostatic capacity of the static electricity countermeasure component 14, the coil component 15 is provided behind the static electricity countermeasure component 14, so that the transmission impedance can be kept large. It is.

  In the above-described embodiment of the present invention, the differential transmission circuit having two signal lines 11 has been described. However, the same effect as that of the above-described embodiment of the present invention can be achieved with one single-ended circuit. Is obtained.

  The anti-static circuit according to the present invention has an effect of suppressing a decrease in transmission impedance, and is useful in an anti-static circuit used for protecting various electronic devices from static electricity.

Schematic diagram of an anti-static circuit in an embodiment of the present invention Equivalent circuit diagram of the static electricity countermeasure circuit Top view of anti-static parts used in the static electricity countermeasure circuit Perspective view of anti-static components used in the same anti-static circuit Diagram showing transmission impedance in the static electricity countermeasure circuit Diagram showing the relationship between capacitance and transmission impedance Voltage waveform diagram applied to IC when electrostatic pulse is applied to the static electricity countermeasure circuit Schematic diagram of an anti-static circuit showing another example of one embodiment of the present invention Equivalent circuit diagram of the static electricity countermeasure circuit Voltage waveform diagram applied to IC when electrostatic pulse is applied to the static electricity countermeasure circuit Diagram showing transmission impedance in the static electricity countermeasure circuit Schematic diagram of a conventional static electricity countermeasure circuit Equivalent circuit diagram of the static electricity countermeasure circuit Voltage waveform diagram applied to IC when electrostatic pulse is applied to the static electricity countermeasure circuit Diagram showing transmission impedance in the static electricity countermeasure circuit

Explanation of symbols

11 signal line 11a one end of signal line 11b other end of signal line 12 IC
DESCRIPTION OF SYMBOLS 13 Ground 14 Antistatic component 15 Coil component 17 Insulating layer 18a, 18b A pair of electrode 19 Voltage-dependent resistance material

Claims (3)

A signal line having one end and the other end connected to the IC, an anti-static component connected between the signal line and the ground, and a coil component connected in series with the signal line, Static electricity countermeasure circuit with electrostatic capacity of 0.3pF or less. The electrostatic countermeasure circuit according to claim 1, wherein the electrostatic countermeasure component is provided closer to one end of the signal line than the coil component. An anti-static component includes one insulating layer, a pair of electrodes provided on the same surface of the one insulating layer or opposite front and back surfaces of the insulating layer, and a voltage-dependent resistance provided between the pair of electrodes. The antistatic circuit according to claim 1, wherein the circuit is made of a material.

Images