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Murata Manufacturing Co., Ltd. has commercialized the world's smallest chip common mode choke coil (*1) DLP0NS for high-speed differential transmission line (*2) anti-noise suppression.

This product is smaller, thinner and lighter than the previous product at 0.85x0.65x0.45mm in dimension, greatly contributing to high-density mounting for compact mobile equipments such as cellular phones and digital cameras. We have also realized the coupling coefficient (*3) of over 0.98, to suppress differential mode impedance for the signal passage band causing degradation in signal waveforms, to a low level. Furthermore, we have tried to align against characteristic impedance (*4) of the transmission line in order to suppress input signal reflection. By doing so, common mode noise alone is effectively removed without affecting high-speed signal waveforms.

Three items with common mode impedance of 67, 90 and 120ohm (typical value at 100MHz) are available in the line-up to allow for a wide range of selections according to applications.

This product does not contain materials regulated by RoHS directive.

We start mass-production on May 2005. We plan to produce 3 million units per month.

Background

Compact mobile equipments such as cellular phones and digital cameras are increasingly becoming more compact, multi-featured, and high-density packaged. Their external interface USB, LVDS to connect to LCDs within equipments, and common mode choke coils used as a measure against the noise from high-speed differential lines are required to become smaller. Also, due to high-speed differential transmission methods such as USB2.0, IEEE 1394, DVI and HDMI for PCs and peripherals are becoming more common, deterioration of signal waveform quality due to input signal reflection, conventionally insignificant, can no longer be ignored. To this end, common mode choke coils that can effectively remove only the noise without affecting signal waveforms by suppressing deterioration of signal and waveform qualities by aligning impedance of noise suppression components to be inserted into the transmission line against characteristic impedance of the transmission line are in demand.

Terminology

*1 Common mode choke coil:
A common mode choke coil is a coil with magnetic combination of more than two coils. It has an ability to remove only common mode constituents without affecting differential mode constituents in the direction of current transmission.

*2 Differential transmission:
Differential transmission is a method to transmit synchronized data over a pair of signal lines. It is strong against noise and suitable for high-speed transmission. Since its structure cancels magnetic flux generated by a differential mode current, it discourages differential mode noise from occurring. Therefore, common mode is the main noise at differential transmission lines.

*3 Coupling coefficient:
Coupling coefficient represents the degree of coupling between coils connected by magnetism. Its maximum value is 1. With common mode choke coil, the higher the coupling coefficient, the lower the differential mode impedance becomes, making the influence to the signal smaller.

*4 Characteristic impedance:
Characteristic impedance is impedance at an arbitrary position of a transmission line. If transmission impedance and load (common mode choke coil) impedance differ, reflection occurs at the load end preventing energy (voltage and current) from transmitting well. Therefore, by synchronizing load impedance and line impedance (characteristic impedance (Z0)), energy may be transmitted to the load without loss.

Features

• Compact and thin at 0.85x0.65x0.45mm in dimension
• Light weight at approximately 1mg
• Inner electrode pitch at 0.5mm
• Noise suppressions are possible without affecting the signal waveforms of high-speed differential transmission lines, due to its high coupling (k>=0.98)
• Maximum of 120ohm (at 100MHz) common mode impedance characteristics in spite of its compactness
• Characteristic impedance is aligned
• Does not use materials regulated by RoHS directive

Applications

Noise suppression at high-speed differential transmission lines (USB2.0, IEEE1394, LVDS, DVI, HDMI, etc.) for compact mobile equipments including digital still cameras, video cameras, cellular phones, PDAs and laptop PCs

Dimensions

Part Number and Specifications

Characteristics

Starting Month for Sales

May 2005

Production Capacity

3 million units per month as of May 2005

Patents

21 patents are pending