CN1553572A - Electromagnetic interference preventing circuit of pluse buffer and method thereof - Google Patents
Electromagnetic interference preventing circuit of pluse buffer and method thereof Download PDFInfo
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- CN1553572A CN1553572A CNA031427502A CN03142750A CN1553572A CN 1553572 A CN1553572 A CN 1553572A CN A031427502 A CNA031427502 A CN A031427502A CN 03142750 A CN03142750 A CN 03142750A CN 1553572 A CN1553572 A CN 1553572A
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- electromagnetic interference
- buffer
- pluse
- magnetic bead
- pluse buffer
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Abstract
An electromagnetic interference preventive circuit for clock buffer and its method are disclosed. A magnetic ball is connected in series at the power supply end of the clock buffer to prevent the clock buffer from external electromagnet interference, and connects a capacitor in parallel at the both end of the magnet ball to reduce the effects to the clock signal after the magnetic ball being installed. It also can maintain the stability of communication device using the clock buffer.
Description
(1) technical field
The preventing circuit and the method for the relevant a kind of electromagnetic interference of the present invention, and particularly relevant for a kind of electromagnetic interference preventing circuit and method of pluse buffer.
(2) background technology
Along with the prosperity of science and technology, the Internet has become the important channel that people obtain new knowledge, also is the main place of recreation and amusement and business transaction.Past, dial and connect formula modem (modem) connects the Internet for PC communication device, now, in order to adapt to the demand of the high-quality multi-media communication of network, product as Asymmetric Digital Subscriber Line various XDSL such as (Asymmetric Digital Subscriber Loop are called for short ADSL) also more is tending towards ripe and universal.In the transceiver integrated circuit (Transceiver IC) of these communication devices; usually can need a clock pulse signal to drive; clock signal then comes from pluse buffer; therefore; electromagnetic interference (Electro-magnetic Interference relevant for pluse buffer; hereinafter to be referred as EMI) anti-system, just become very important problem in the anti-system technology of EMI of above-mentioned communication device.
Generally speaking, though can use a magnetic bead (Ferrite bead) of the power end that is serially connected with pluse buffer, be used as the anti-system measure of EMI of pluse buffer, but because the inductance characteristic of magnetic bead, therefore also can have influence on the waveform of the output clock signal of pluse buffer.As shown in Figure 1, be the waveform of the I/O clock signal that when the power end serial connection magnetic bead of pluse buffer, measures, show among the figure, the waveform of this output clock signal clk-out is subjected to the influence of the power end serial connection magnetic bead of pluse buffer, the high low level that causes exporting clock signal clk-out is extremely not obvious, this kind clock signal will cause the communication device instability, even the situation that can't work.So, when the electromagnetic interference that pluse buffer is arranged is prevented the system demand, just be absorbed in and stand the apparatus function instability, or set about, so that expend facing a difficult choice of great amount of cost by other device places.
(3) summary of the invention
In view of this, the invention provides a kind of electromagnetic interference preventing circuit and method of pluse buffer, except the purpose that can reach the anti-system of electromagnetic interference, more can keep and use the communication device of this clock pulse buffer stably to work.
For reaching above-mentioned and other purpose, the invention provides a kind of electromagnetic interference preventing circuit of pluse buffer.The electromagnetic interference preventing circuit of this clock pulse buffer comprises: pluse buffer, magnetic bead and capacitor.Wherein, pluse buffer is in order to receive a clock pulse signal, and this clock signal of buffering output, magnetic bead is serially connected with the power end of pluse buffer, with suffering external electromagnetic interference (as power supply) in case make this pluse buffer, capacitor then is connected to the two ends of magnetic bead, in order to behind the reducing apparatus magnetic bead for the influence of clock signal.
In one embodiment, the magnetic bead that the electromagnetic interference preventing circuit of this clock pulse buffer uses, its impedance characteristic has the highest resistance value at the electromagnetic frequency place of the anti-system of desire.For example, when the electromagnetic frequency of the anti-system of desire is 1 25MHz, then the spike of the impedance characteristic of magnetic bead is when occurring in frequency and being 125MHz, so that can strengthen the electromagnetic interference effect of control of the electromagnetic frequency of the anti-system of desire.
In one embodiment, the capacitor that the electromagnetic interference preventing circuit of this clock pulse buffer uses, its impedance characteristic has minimum resistance value at the frequency place of aforementioned clock signal.For example, when the frequency of clock pulse signal is 25MHz, then the trough of the impedance characteristic of capacitor is when occurring in frequency and being 25MHz, so that can significantly lower the influence of magnetic bead for clock signal.
The present invention provides a kind of electromagnetic interference of pluse buffer anti-system method in addition, and it is applicable to the electromagnetic interference of anti-system one clock pulse buffer.The anti-system method of the electromagnetic interference of this clock pulse buffer comprises the following steps: to be connected in series a magnetic bead at the power end of pluse buffer, so that anti-this pluse buffer of system suffers external electromagnetic interference (as power supply); And at the two ends of magnetic bead and connect a capacitor, so that lower the influence of magnetic bead for the clock signal that pluse buffer cushioned.
Wherein, can select impedance characteristic the magnetic bead of the highest resistance value to be arranged, so that what can strengthen the anti-system of desire for example is the electromagnetic interference effect of control of 125MHz electromagnetic frequency at the electromagnetic frequency place of the anti-system of desire.
Wherein, can select impedance characteristic that the capacitor of minimum resistance value is arranged at the frequency place of the clock signal of pluse buffer, so that can significantly lower magnetic bead for the influence that for example is the 25MHz clock signal.
By in the above-mentioned explanation as can be known, the electromagnetic interference preventing circuit and the method for a kind of pluse buffer provided by the present invention, reach the anti-purpose of making of electromagnetic interference except using magnetic bead, also at the other shunt capacitor of magnetic bead, so that significantly lower the influence of magnetic bead, use the communication device of this clock pulse buffer stably to work and can keep for clock signal.
For above-mentioned and other purposes of the present invention, characteristics and advantage can be become apparent, below special with preferred embodiment, and conjunction with figs. is elaborated.
(4) description of drawings
Fig. 1 is the waveform of the I/O clock signal that measures when being presented at the power end serial connection magnetic bead of pluse buffer;
Fig. 2 shows a kind of electromagnetic interference preventing circuit of pluse buffer according to an embodiment of the invention; And
Fig. 3 shows a kind of element impedance performance diagram of electromagnetic interference preventing circuit of pluse buffer according to an embodiment of the invention.
(5) embodiment
Please refer to shown in Figure 2ly, it is the electromagnetic interference preventing circuit of a kind of pluse buffer according to an embodiment of the invention.As previously mentioned, in order to reach the purpose of the anti-system of electromagnetic interference, can keep again simultaneously and use the communication device of this clock pulse buffer 210 stably to work.Therefore, such as shown in the figure, the electromagnetic interference preventing circuit 200 of this clock pulse buffer comprises: pluse buffer 210, magnetic bead 220 and capacitor 230.
Wherein, pluse buffer 210 receives clock signal clk-in, and its buffering output is become clock signal clk-out, with the transceiver integrated circuit (not illustrating) that drives communication device etc.Because in the anti-system of the electromagnetic interference of communication device, clock signal is the main source of electromagnetic interference normally,, promptly find that through experiment test it is the electromagnetic interference source of 125MHz that a frequency is arranged in the power end of pluse buffer 210 with present embodiment.
So, as described above, use the power end Vcc that magnetic bead 220 is serially connected with pluse buffer 220, with to suffer frequency be the electromagnetic interference of 125MHz in case make this pluse buffer, and in order to strengthen the electromagnetic interference effect of control of the anti-electromagnetic frequency 125MHz that makes of desire, therefore, the impedance characteristic of the magnetic bead of selecting for use 220, the resistance value when the electromagnetic frequency of 125MHz is for the highest.Please refer to the element impedance performance diagram of Fig. 3, wherein to be the model that present embodiment selects for use be the impedance characteristic of the magnetic bead of MLB-201209-450B-N3 to the curve of label A, as can be seen from Figure, the spike of the impedance characteristic of this magnetic bead is when betiding frequency and being 125MHz, and to suffer frequency be the effect of the electromagnetic interference of 125MHz to reach preferable this pluse buffer of anti-system.
In addition,, form waveform, cause using the situation that the communication device of this clock pulse buffer 210 can't operate as normal as the clock signal clk-out of Fig. 1 for fear of behind the power end Vcc of pluse buffer 220 serial connection magnetic bead 220.Therefore, present embodiment is in addition in the two ends of magnetic bead 220 and connect capacitor 230, so as can reducing apparatus magnetic bead 220 backs for the influences of clock signal clk-out.Wherein, reduce to minimumly for the influence of clock signal clk-out, can select for use impedance characteristic that the capacitor 230 of minimum resistance value is arranged at the frequency place of clock signal clk-out in order to install magnetic bead 220 back.Because the frequency of herein clock signal clk-out is 25MHz, so such shown in the curve of Fig. 3 label B, the trough of the impedance characteristic of the 4.7 μ F capacitors 230 that present embodiment is selected for use is when occurring in frequency and being 25MHz.In Fig. 3, by the synthetic impedance characteristic of magnetic bead 220 and capacitor 230 then shown in the curve of label C.
In above-mentioned explanation, can conclude a kind of anti-system method of electromagnetic interference of pluse buffer, it is applicable to the electromagnetic interference of anti-system one clock pulse buffer.The anti-system method of the electromagnetic interference of this clock pulse buffer comprises the following steps: to be connected in series a magnetic bead at the power end of pluse buffer, suffers electromagnetic interference in case make this pluse buffer; And at the two ends of magnetic bead and connect a capacitor, to lower the influence of magnetic bead for the clock signal of pluse buffer buffering.
Wherein, can select impedance characteristic the magnetic bead of the highest resistance value to be arranged, so that what can strengthen the anti-system of desire for example is the electromagnetic interference effect of control of 125MHz electromagnetic frequency at the electromagnetic frequency place of the anti-system of desire.
Wherein, also can select impedance characteristic that the capacitor of minimum resistance value is arranged at the frequency place of the clock signal of pluse buffer, so that can significantly lower magnetic bead for the influence that for example is the 25MHz clock signal.
In sum, the present invention has following advantage at least:
1. can reach the purpose of the anti-system of electromagnetic interference.
2. can keep and use the communication device of this clock pulse buffer still stably to work.
3. owing to be to prevent the system electromagnetic interference by the pluse buffer of main electromagnetic interference source, not only effect is more remarkable, and the cost of cost can minimize.
Though the present invention discloses as above with preferred embodiment; yet it is not in order to limit the present invention; any person skilled in the art person without departing from the spirit and scope of the present invention; when can making various changes and replacement, so protection scope of the present invention is when looking being as the criterion that accompanying Claim defines.
Claims (10)
1. the electromagnetic interference preventing circuit of a pluse buffer comprises:
One clock pulse buffer, in order to receiving a clock pulse signal, and this clock signal of buffering output;
One magnetic bead is serially connected with the power end of this pluse buffer, with suffering electromagnetic interference in case make this pluse buffer; And
One capacitor is connected to the two ends of this magnetic bead, in order to lower the influence of this magnetic bead for this clock signal.
2. the electromagnetic interference preventing circuit of pluse buffer as claimed in claim 1 is characterized in that, the impedance characteristic of this magnetic bead has the highest resistance value at this electromagnetic frequency place.
3. the electromagnetic interference preventing circuit of pluse buffer as claimed in claim 1 is characterized in that, this electromagnetic frequency is 125MHz.
4. the electromagnetic interference preventing circuit of pluse buffer as claimed in claim 1 is characterized in that, the impedance characteristic of this capacitor has minimum resistance value at the frequency place of this clock signal.
5. the electromagnetic interference preventing circuit of pluse buffer as claimed in claim 1 is characterized in that, the frequency of this clock signal is 25MHz.
6. the anti-system method of the electromagnetic interference of a pluse buffer is applicable to the anti-electromagnetic interference of making a clock pulse buffer, comprises the following steps:
Power end at this pluse buffer is connected in series a magnetic bead, so that anti-this pluse buffer of system suffers electromagnetic interference; And
At the two ends of this magnetic bead and connect a capacitor, to lower of the influence of this magnetic bead for a clock pulse signal of this pluse buffer buffering.
7. the anti-system method of the electromagnetic interference of pluse buffer as claimed in claim 6 is characterized in that the impedance characteristic of this magnetic bead has the highest resistance value at this electromagnetic frequency place.
8. the anti-system method of the electromagnetic interference of pluse buffer as claimed in claim 6 is characterized in that this electromagnetic frequency is 125MHz.
9. the anti-system method of the electromagnetic interference of pluse buffer as claimed in claim 6 is characterized in that the impedance characteristic of this capacitor has minimum resistance value at the frequency place of this clock signal.
10. the anti-system method of the electromagnetic interference of pluse buffer as claimed in claim 6 is characterized in that the frequency of this clock signal is 25MHz.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 03142750 CN1553572B (en) | 2003-06-06 | 2003-06-06 | Electromagnetic interference preventing circuit of pluse buffer and method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 03142750 CN1553572B (en) | 2003-06-06 | 2003-06-06 | Electromagnetic interference preventing circuit of pluse buffer and method thereof |
Publications (2)
| Publication Number | Publication Date |
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| CN1553572A true CN1553572A (en) | 2004-12-08 |
| CN1553572B CN1553572B (en) | 2011-08-10 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 03142750 Expired - Lifetime CN1553572B (en) | 2003-06-06 | 2003-06-06 | Electromagnetic interference preventing circuit of pluse buffer and method thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106656115A (en) * | 2016-10-19 | 2017-05-10 | 延锋伟世通电子科技（上海）有限公司 | Long distance clock signal EMI inhibition circuit |
| CN107959485A (en) * | 2017-11-30 | 2018-04-24 | 郑州云海信息技术有限公司 | A kind of method for improving Electro Magnetic Compatibility |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6252313B1 (en) * | 1997-12-15 | 2001-06-26 | Intel Corporation | Apparatus and method for minimizing electromagnetic interference in microcomputing systems |
-
2003
- 2003-06-06 CN CN 03142750 patent/CN1553572B/en not_active Expired - Lifetime
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106656115A (en) * | 2016-10-19 | 2017-05-10 | 延锋伟世通电子科技（上海）有限公司 | Long distance clock signal EMI inhibition circuit |
| CN106656115B (en) * | 2016-10-19 | 2023-06-30 | 延锋伟世通电子科技（上海）有限公司 | Long-distance clock signal EMI suppression circuit |
| CN107959485A (en) * | 2017-11-30 | 2018-04-24 | 郑州云海信息技术有限公司 | A kind of method for improving Electro Magnetic Compatibility |
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| Publication number | Publication date |
|---|---|
| CN1553572B (en) | 2011-08-10 |
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Granted publication date: 20110810 |