JP2000132262A - Clock driver and method for attenuating radiation noise - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attenuate radiation noise, also to suppress signal distortion by preventing the radiation noise from being superimposed on a signal and also to improve transmission efficiency. SOLUTION: This radiation noise attenuating method reduces a current loop area caused by a high frequency current and attenuates radiation noise by suppressing the high frequency current including high frequency components that become the causes of the radiation noise from a normal clock output buffer circuit 1 side and signal distortion by an inductor 4 and also transmitting it to the ground through a capacitor 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a clock driver and a radiation noise attenuator which attenuate radiation noise generated from a clock driver (clock output IC) which is a source of radiation noise and eliminate signal distortion. About the method.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 9-6482 discloses a technique for reducing radiation noise in data communication.
A data communication device disclosed in Japanese Patent Application Laid-Open No. 6-206 is known. This is to limit the amount of current that can be sent out by the driver circuit by providing a terminating circuit on the transmission line and setting the current flowing through the terminating circuit to a value smaller than the maximum amount of current that can be sent out by the driver circuit. Things.

[0003]

However, in the above-mentioned prior art, since the amount of current that can be transmitted from the driver circuit is simply limited, the radiation noise and signal distortion generated from the driver circuit side are reduced. It has become difficult to attenuate high-frequency currents that include high-frequency components that cause them. For this reason, radiation noise from the driver circuit side is superimposed on the data transmitted to the transmission line, which not only impairs the suppression of signal distortion but also hinders the improvement of transmission efficiency. .

[0004] The present invention has been made in view of such circumstances, and a clock driver and a radiation driver capable of attenuating radiation noise, suppressing signal distortion, and improving transmission efficiency. It is intended to provide a noise attenuation method.

[0005]

According to a first aspect of the present invention, there is provided a clock driver, wherein an output of a normal clock output buffer circuit is connected to one end of a high-frequency current suppressing element, and an output of the normal clock output buffer circuit is connected to a high-frequency current suppressing element. One end of the high-frequency current transmitting element is connected to one end of the element, and the other end of the high-frequency current transmitting element is connected to the ground. The high-frequency current suppressing element may be an inductor, and the high-frequency current transmitting element may be a capacitor. Further, the inductor may have an inductance value that is larger than the impedance of the capacitor. Claim 4
The radiation noise attenuating method described in the above, the first step of suppressing the high-frequency current including the high-frequency component output from the normal clock output buffer circuit by the high-frequency current suppression element, and the high-frequency component output from the normal clock output buffer circuit And transmitting a high-frequency current to the ground via the high-frequency current transmitting element. Further, in the first step, the element for suppressing the high-frequency current may be an inductor. Further, in the second step, the element to be sent to the high-frequency current ground may be a capacitor.
Further, the high-frequency current suppressing element may have an impedance value that is larger than the impedance of the high-frequency current transmitting element. The low radiated noise clock driver of the present invention suppresses a high frequency current including a high frequency component which causes a radiation noise and a signal distortion from the clock output buffer circuit side by a high frequency current suppressing element and a high frequency current transmitting element. To the ground.

[0006]

Embodiments of the present invention will be described below. FIG. 1 is a circuit diagram showing one embodiment of the clock driver of the present invention. As shown in FIG. 1, the clock driver normally includes a clock output buffer circuit 1, a capacitor 3, and an inductor 4. The output section 2 of the normal clock output buffer circuit 1 and one end of the inductor 4 are connected. One end of the capacitor 3 is connected between the output unit 2 of the normal clock output buffer circuit 1 and one end of the inductor 4. The other end of the capacitor 3 is connected to the ground.

The other end of the inductor 4 is connected to an output pin 5 of a clock driver. Here, inductor 4
Has an inductance value that is larger than the impedance of the capacitor 3. This is to allow the high frequency current to flow to the low impedance capacitor 3 side. A receiving unit 7 is connected to the output pin 5 via a transmission line 6.

[0008] The clock driver having such a configuration performs the following operation. First, as described above, the inductor 4 has an inductance value that is larger than the impedance of the capacitor 3. Therefore, a high-frequency current including a high-frequency component output from the normal clock output buffer circuit 1 is suppressed by the inductor 4 and flows to the ground via the capacitor 3. As a result, the distance between the capacitor 3 and the output unit 2 approaches zero as much as possible, so that the current loop area between the capacitor 3 and the output unit 2 approaches zero. As the current loop area approaches zero, radiation noise emitted from the clock driver side is attenuated.

Further, the high frequency current from the normal clock output buffer circuit 1 does not flow to the transmission line 6 side. For this reason, the signal transmitted to the receiving unit 7 does not include high-frequency components that cause radiation noise and signal distortion.
A stable signal is supplied without waveform distortion.

As described above, in the present embodiment, the high-frequency current including the high-frequency component which causes the radiation noise and the signal distortion from the clock output buffer circuit 1 side is suppressed by the inductor 4 and the high-frequency current including the high-frequency current via the capacitor 4. To be sent to the ground. As a result, the current loop area due to the high-frequency current can be reduced, and the radiation noise can be attenuated. In addition, since radiation noise is not superimposed on the signal, distortion of the signal supplied to the receiving unit 7 via the transmission line 6 is eliminated, and a stable signal can be supplied to the receiving unit 7 and transmission efficiency is improved. Can be improved. Further, the radiation noise from the normal clock output buffer circuit 1 is suppressed, so that the transmission line length of the transmission line 6 can be increased.

[0011]

As described above, according to the low radiated noise clock driver of the present invention, the radiated noise from the clock output buffer circuit side and the high frequency current including the high frequency component which causes the signal distortion are normally generated by the high frequency current suppressing element. In addition to the suppression, the signal is sent to the ground via the high-frequency current sending element, so that the radiated noise can be attenuated. Moreover, by not superimposing the radiated noise on the signal, the signal distortion is suppressed and the transmission efficiency is reduced. Can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a clock driver of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Normal clock output buffer circuit 2 Output part 3 Capacitor 4 Inductor 5 Output pin 6 Transmission line 7 Receiver

Claims (7)

[Claims] 1. An output section of a normal clock output buffer circuit and one end of a high-frequency current suppression element are connected, and a high-frequency current transmission element is connected between the output section of the normal clock output buffer circuit and one end of the high-frequency current suppression element. A clock driver having one end connected and the other end of the high-frequency current transmitting element connected to ground. 2. The clock driver according to claim 1, wherein the high-frequency current suppressing element is an inductor, and the high-frequency current transmitting element is a capacitor. 3. The clock driver according to claim 2, wherein the inductor has an inductance value that is larger than the impedance of the capacitor. 4. A first step of suppressing a high-frequency current including a high-frequency component output from a normal clock output buffer circuit by a high-frequency current suppressing element, and a high-frequency current including a high-frequency component output from the normal clock output buffer circuit. And a second step of transmitting to a ground via a high-frequency current transmitting element. 5. The method according to claim 4, wherein in the first step, the element for suppressing the high-frequency current is an inductor. 6. The radiation noise attenuation method according to claim 4, wherein in the second step, an element to be sent to the high-frequency current ground is a capacitor. 7. The radiation noise attenuation method according to claim 4, wherein the high-frequency current suppressing element has an impedance value larger than the impedance of the high-frequency current transmitting element.