CN206481279U - Long range clock signal EMI suppression circuits - Google Patents

Abstract

A kind of long range clock signal EMI suppression circuits, solution is the technical problem for suppressing clock signal EMI.The circuit includes signal repeater, magnetic bead, first resistor, the first inductor, the first capacitor, the second capacitor, the 3rd capacitor, the first clamp diode, the second clamp diode, and at least one signal source of clock；The output end of each signal source of clock connects first resistor to the input of signal repeater by magnetic bead, and the input of signal repeater terminates the first capacitor to ground；The output of the signal repeater terminates the first clamp diode to ground, and the output of signal repeater terminates the second capacitor to ground；The output end of the input termination signal repeater of first inductor, the output of the first inductor terminates the 3rd capacitor to ground, and the output of the first inductor terminates the second clamp diode to ground.The circuit that the utility model is provided, is particularly suitable for use in the clock signal of long range cabling.

Description

Long range clock signal EMI suppression circuits

Technical field

The utility model is related to electricity field, more particularly to automotive electronic technology, particularly a kind of long range clock signal EMI suppression circuits.

Background technology

For the EMI of clock signal（Electromagnetic interference）Restrain measurement mainly has ground connection, shielding, filtering and several tradition of spread spectrum Method, but under automotive electronics increasingly complex environment, this several conventional method has following defect：

1）EMI is suppressed using earthing method：Because vehicle electronics volume is smaller, it is easy between each functional module There is crosstalk phenomenon, when the frequency of clock signal is fallen into the operating frequency range of other modules, pressed down using earthing method EMI processed can reduce the stability of other modules work.

2）EMI is suppressed using metallic shield：This method is merely able to reduce the interference that correlation module gives off, for Clock signal through long-distance PCB trace, this method can not be reduced by transmitting EMI problems caused by beta radiation.

3）EMI is suppressed using filtering method：It is simple to reduce the amplitude and phase of clock signal waveform, meeting using filtering Influence the job stability of circuit.

4）EMI is suppressed using spread spectrum method：This method is, by energy spread, the peak energy of clock signal to be expanded Open up in certain band limits, reduce the interference value of clock peak value by this method, but for long range cabling when Clock signal, spread spectrum may be such that the interference signal of more multi-frequency is radiate by PCB trace and FFC, increase EMI risk, Secondly it can not also realize by spread spectrum to reduce the energy of clock signal peak value for the chip without spread spectrum technology.

Utility model content

For defect present in above-mentioned prior art, technical problem to be solved in the utility model is to provide a kind of energy Effectively suppress the EMI of the clock signal of long range cabling long range clock signal EMI suppression circuits.

In order to solve the above-mentioned technical problem, a kind of long range clock signal EMI suppression circuits provided by the utility model, It is characterized in that：Including signal repeater, magnetic bead, first resistor device, the first inductor, the first capacitor, the second capacitor, Three capacitors, the first clamp diode, the second clamp diode, and at least one signal source of clock；

The output end of each signal source of clock connects first resistor device to the input of signal repeater by magnetic bead, and believes The input of number repeater terminate the first capacitor to；

The output of the signal repeater terminates the first clamp diode to ground, and the output of signal repeater terminates the Two capacitors to ground；

The output end of the input termination signal repeater of first inductor, the electricity of output termination the 3rd of the first inductor Container is to ground, and the output of the first inductor terminates the second clamp diode to ground.

The long range clock signal EMI suppression circuits that the utility model is provided, High-frequency Interference is absorbed using magnetic bead, is utilized Resistance reduces the radiation of higher frequency signal energy externally with the frequency low pass ripple of electric capacity composition, is prevented using clamp diode The interference of electrostatic surge pulse, and shaping is carried out using pi type filter, can be to clock phase offset correction, raising front end drop Low clock amplitude, can also filter out the CLK higher hamonic wave signals that processor chips are reflected, can effectively suppress long range cabling Clock signal EMI, reduce the radiation of overall frequency domain, while do not influence the phase and amplitude of clock signal again, and And circuit cost is relatively low, while having good inhibition to EMC radiation etc. again, simultaneously for the radio reception inside automotive electronics Beat noise reductions in machine part have good inhibition.

Brief description of the drawings

Fig. 1 is the circuit diagram of the long range clock signal EMI suppression circuits of the utility model embodiment；

Clock signal waveform when Fig. 2 is the long range clock signal EMI suppression circuits work of the utility model embodiment Figure.

Embodiment

Below in conjunction with brief description of the drawings embodiment of the present utility model is described in further detail, but the present embodiment and without It is every to use similar structure of the present utility model and its similar change in limitation the utility model, the utility model all should be included in Protection domain, the pause mark in the utility model represents the relation of sum.

As shown in figure 1, a kind of long range clock signal EMI suppression circuits that the utility model embodiment is provided, it is special Levy and be：Including signal repeater U1, magnetic bead ATTN1, first resistor device R1, the first inductor L1, the first capacitor C1, second Capacitor C2, the 3rd capacitor C3, the first clamp diode D1, the second clamp diode D2, and at least one signal source of clock CLOCK；

Each signal source of clock CLOCK output end meets first resistor device R1 to signal repeater U1 by magnetic bead ATTN1 Input, and signal repeater U1 input terminate the first capacitor C1 to；

The output of the signal repeater U1 terminate the first clamp diode D1 to, and signal repeater U1 output The second capacitor C2 is terminated to ground；

The input termination signal repeater U1 of first inductor L1 output end, the first inductor L1 output termination 3rd capacitor C3 is to ground, and the first inductor L1 output terminates the second clamp diode D2 to ground.

The operation principle of the utility model embodiment is as follows：

The applicable cases of transmission over long distances are needed for clock signal, when length of transmission line exceedes the 1/ of interference signal wavelength When 20, transmission line can all launch interference signal as an effective antenna, in order to caused by preventing long range cabling Radiation-emitting is exceeded, and the best way seeks to reduce in source the energy of interference signal；

The clock signal of signal source of clock CLOCK output sequentially passes through magnetic bead ATTN1, first resistor device R1, magnetic bead pair High-frequency Interference has absorption, can not only prevent because resonance causes other EMI problems, and can prevent high frequency from believing Number it is radiate in clock signal output terminal by PCB, so as to avoid high frequency E MI exceeded；First resistor device R1 is used to drop The amplitude of low-clock signal, can so effectively reduce the radiation of fundamental frequency energy externally；First resistor device R1 and the first electric capacity Device C1 constitutes frequency low pass wave mode, further the radiation of reduction higher frequency signal energy externally；First clamp diode D1 is used for Clamp signal amplitude voltage, is allowed to control within the specific limits；Second clamp diode D2 is used for clamp signal amplitude voltage, makes Control in certain limit, while preventing electrostatic surge pulse from disturbing signal input part；Second capacitor C2, the first inductance Device L1, the 3rd capacitor C3 constitute pi type filter, pi type filter on the one hand can for realize to clock phase offset correction, The clock amplitude of front end reduction is improved, the CLK higher hamonic wave signals that processor chips are reflected on the other hand can also be filtered out, prevented Only these high-frequency energies influence the EMI performances of complete machine by space radiation.

The utility model embodiment is particularly suitable for use in the clock signal of transmission over long distances, can reduce the spoke of overall frequency domain Penetrate, while not influenceing the phase and overall amplitude of clock signal again, circuit function and performance are preferably balanced.

Sine wave, square wave frequency of the utility model embodiment for 108MHz, fundamental frequency 108MHz and its frequency multiplication 108MHz* N（N is odd number）, half frequency multiplication 54MHz and its strange frequency multiplication 54MHz*N（N is odd number）, 27MHz and strange frequency multiplication 27MHz*N（N is strange Number）, 13.5MHz and its strange frequency multiplication 13.5MHz*N（N is odd number）Radiation at these frequencies has good inhibition, right There is good inhibition in internal radio part 94.5MHz, 108MHz beat noise.

Sine wave, square wave frequency of the utility model embodiment for 54MHz, fundamental frequency 54MHz and its frequency multiplication 54MHz*N（N For integer）, half frequency multiplication 27MHz and its frequency multiplication 27MHz*N（N is integer）, 13.5MHz and its frequency multiplication 13.5MHz*N（N is integer） Radiation at these frequencies has good inhibition, for internal radio part 94.5MHz, 108MHz beat Noise has good inhibition.

Clock signal waveform when Fig. 2 is the long range clock signal EMI suppression circuits work of the utility model embodiment Waveform S1 in figure, Fig. 2 is the output signal of signal source of clock, and waveform S2 is the clock signal in transmission, and waveform S3 is final The clock signal of output.

Claims (1)

1. a kind of long range clock signal EMI suppression circuits, it is characterised in that：Including signal repeater, magnetic bead, first resistor Device, the first inductor, the first capacitor, the second capacitor, the 3rd capacitor, the first clamp diode, the second clamp diode, And at least one signal source of clock；

The output end of each signal source of clock connects first resistor device to the input of signal repeater by magnetic bead, and in signal Input after device terminates the first capacitor to ground；

The output of the signal repeater terminates the first clamp diode to ground, and the output termination second of signal repeater is electric Container to ground；

The output end of the input termination signal repeater of first inductor, the output of the first inductor terminates the 3rd capacitor Output to ground, and the first inductor terminates the second clamp diode to ground.