EMI Suppression Filters for Digital Equipment by Murata Manufacturing Co.,Ltd.

More catalogs by Murata Manufacturing Co.,Ltd. | EMI Suppression Filters for Digital Equipment | 57 pages | 2006-11-24

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Industrial Supply > Electrical & Test > Electronic Components > Passive Components > Fuses & Circuit Protection

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!note please read rating and !caution for storage operating rating soldering mounting and handling in this pdf catalog to prevent smoking and/or burning etc this catalog has only typical specifications therefore you are requested to approve our product specifications or to transact the approval sheet for product specificaions before ordering c33e.pdf 04.5.12 1 noise sources in digital equipment yyyyyyyyy02 1 digital signals and harmonic components 03 example of digital s spectrum measurement 04 noise in ic power supply line 05 2 radiated noise from digital circuit boards 06 noise generated by ic 06 radiated noise from patterns 07 effect of emi suppression filter 08 3 radiated noise from cables 09 radiated noise from cable 1 09 example of suppressing radiated noise from cable 1 10 radiated noise from cable 2 11 radiated noise from cable 3 12 example of suppressing radiated noise from cable 2 13 radiated noise from cable 4 14 example of suppressing radiated noise from cable

!note please read rating and !caution for storage operating rating soldering mounting and handling in this pdf catalog to prevent smoking and/or burning etc this catalog has only typical specifications therefore you are requested to approve our product specifications or to transact the approval sheet for product specificaions before ordering c33e.pdf 04.5.12 noise sources in digital equipment 1 radiated noise from patterns now we will show an experimental circuit with a noise source connected to a signal pattern that serves as a noise antenna as shown in the diagram above the ic2 output terminal which is open in the previous experiment is connected to an approx 10cm signal pattern and the signal pattern is terminated with ic3 the noise radiation measurement from this pwb is shown in the chart above from noting the harmonics with the ic oscillation frequency i.e 16mhz on this chart you can see that the noise levels at some frequencies exceed the cisprpub.22 limit value this phenomenon

!note please read rating and !caution for storage operating rating soldering mounting and handling in this pdf catalog to prevent smoking and/or burning etc this catalog has only typical specifications therefore you are requested to approve our product specifications or to transact the approval sheet for product specificaions before ordering c33e.pdf 04.5.12 1 noise sources in digital equipment radiated noise from cable 3 this experiment is intended to examine whether the noise conducted through the cable in the previous experiment is flowing on the signal line or gnd line of the cable in this experiment we measured the radiation noise level by connecting either the signal line or gnd line the noise levels with only the signal line or the gnd line are almost equal to the noise level observed with both these lines the charts show the noise levels with only the gnd line after the signal line is disconnected from the results of this experiment we can see that the same level of noise is

!note please read rating and !caution for storage operating rating soldering mounting and handling in this pdf catalog to prevent smoking and/or burning etc this catalog has only typical specifications therefore you are requested to approve our product specifications or to transact the approval sheet for product specificaions before ordering c33e.pdf 04.5.12 2 suppressing emi noise emission this chapter provides techniques for using emi suppression filters to suppress noise radiation from a pwb for your reference on pwb design we will present the noise measurement data taken by changing the component or pattern layout on a pwb and by improving the gnd condition furthermore for your reference on pwb shielding we will present the measurement data on variations in noise suppressing effect depending on the opening dimension of the shielding 2 1 approaches to suppressing emission of emi noise emi noise emission suppression model these diagrams show the noise suppression models of a pwb

!note please read rating and !caution for storage operating rating soldering mounting and handling in this pdf catalog to prevent smoking and/or burning etc this catalog has only typical specifications therefore you are requested to approve our product specifications or to transact the approval sheet for product specificaions before ordering c33e.pdf 04.5.12 suppressing emi noise emission 2 3 improved ground pattern as a technique for suppressing common mode noise we can consider intensification of the gnd condition when a signal return current flows through the gnd line a voltage applied to the gnd terminal causes common mode noise to suppress such voltage on the gnd terminal we must reduce the gnd impedance between the signal sending and receiving ics with attention to the high speed signal in the circuit in order to prevent noise interference between circuit blocks we must reduce the gnd impedance between individual circuit blocks so that the gnd current from individual circuit

!note please read rating and !caution for storage operating rating soldering mounting and handling in this pdf catalog to prevent smoking and/or burning etc this catalog has only typical specifications therefore you are requested to approve our product specifications or to transact the approval sheet for product specificaions before ordering c33e.pdf 04.5.12 2 suppressing emi noise emission influence of transmission line length these charts show the variations in noise level depending on changes in transmission line length at the same signal frequencies you can see that the noise level increases particularly at low frequencies as the transmission line is extended !experimental pwb 29.7cm 25mhz resonator ceralockĀ® 5v 7cm 3.3v transmission line length l=5cm ferrite beads x=1cm 74hcu04 74lvc04 74lvc00 10cm 20cm 3.3v 2 !radiated noise and signal waveform actual measurement double-sided epoxy-glass pwb the back surface of the pwb is entirely grounded thickness t=0.8mm =4.7 characteristic

!note please read rating and !caution for storage operating rating soldering mounting and handling in this pdf catalog to prevent smoking and/or burning etc this catalog has only typical specifications therefore you are requested to approve our product specifications or to transact the approval sheet for product specificaions before ordering c33e.pdf 04.5.12 3 how to select and use emi suppression filters this chapter describes how to select emi suppression filters for noise suppression and how to use the emi suppression filters effectively by referring to examples of emi suppression filter applications in typical circuits relation between emi filters noise suppression performance and signal waveform distortion 1 generally emi suppression filters are low pass filters which will distort the signal waveform while eliminating noise therefore when selecting emi suppression filters we should pay attention to the signal waveform quality the noise suppressing effects of the capacitor type

!note please read rating and !caution for storage operating rating soldering mounting and handling in this pdf catalog to prevent smoking and/or burning etc this catalog has only typical specifications therefore you are requested to approve our product specifications or to transact the approval sheet for product specificaions before ordering c33e.pdf 04.5.12 how to select and use emi suppression filters 3 4 examples of emi suppression filter use on conductive noise path 1 signal cable connecting section if a larger noise suppressing effect is required you should use the chip emifilĀ® or capacitor type emi suppression filter in combination with a chip ferrite beads inductor if a relatively low noise suppressing effect is enough for the line you may use just the chip ferrite beads inductor to utilize the capacitor type emi suppression filter more effectively you must connect the gnd terminal of the emi suppression filter to a stable ground if a stable ground is not available you should

!note please read rating and !caution for storage operating rating soldering mounting and handling in this pdf catalog to prevent smoking and/or burning etc this catalog has only typical specifications therefore you are requested to approve our product specifications or to transact the approval sheet for product specificaions before ordering c33e.pdf 04.5.12 4 differences in noise suppressing effect caused by transmission line length current distribution change after connection of ferrite beads inductor now the current distribution prior to connection of the ferrite beads inductor is compared with the data after connection of the inductor to compare the current distributions our attention is focused on the data at 375mhz because we observed a remarkable difference in the ferrite beads inductor s noise suppressing effect at 375mhz when the transmission line length on the prototype experimental pwb was changed the charts above show the measurements of current distributions for

!note please read rating and !caution for storage operating rating soldering mounting and handling in this pdf catalog to prevent smoking and/or burning etc this catalog has only typical specifications therefore you are requested to approve our product specifications or to transact the approval sheet for product specificaions before ordering c33e.pdf 04.5.12 differences in noise suppressing effect caused by transmission line length 4 measurement result on shift of ferrite beads inductor mounting position these charts show the radiation noise level measurements when shifting the ferrite beads inductor to the peak current point at a frequency of 375mhz contrary to our expectation the radiation noise level measured at 375mhz is higher than the initial value to examine the cause of this phenomenon we measured the current distribution at 375mhz the charts also show the current distribution measurements when the ferrite beads inductor is moved away from the transmission terminal the current

!note please read rating and !caution for storage operating rating soldering mounting and handling in this pdf catalog to prevent smoking and/or burning etc this catalog has only typical specifications therefore you are requested to approve our product specifications or to transact the approval sheet for product specificaions before ordering c33e.pdf 04.5.12 note 1 export control for customers outside japan murata products should not be used or sold for use in the development production stockpiling or utilization of any conventional weapons or mass-destructive weapons nuclear weapons chemical or biological weapons or missiles or any other weapons for customers in japan for products which are controlled items subject to the foreign exchange and foreign trade law of japan the export license specified by the law is required for export 2 please contact our sales representatives or product engineers before using the products in this catalog for the applications listed below which