What about low-capacitance EMI filters with improved performance?

Last Update Time: 2020-11-03 12:08:19

In order to meet the contradictory requirements of implementing a low-capacitance filter while maintaining high filtering performance, a semiconductor company has developed a new generation of EMI filters with high frequency attenuation characteristics at 900 MHz and an ultra-low capacitance structure.

These new EMI filters based on IPAD technology (integrated active and passive components) use a standard PI filter structure with integrated ESD protection. This new low-capacitance structure is used to provide a cut-off frequency in the 200MHz range and can support data rates with clock frequencies in excess of 40MHz.

Although the diode capacitance has been greatly reduced to 8.5pF, it can provide excellent filtering performance, that is, attenuation characteristics better than -35dB in the frequency range of about 900MHz.

In addition to the filtering function, the integrated input Zener diode can also suppress the ESD impact of air discharge up to 15kV, reaching the performance level required by the IEC61000-4-2 level 4 industry standard.

High-speed data compatibility

In order not to disturb the video signal, the new low-capacitance filter is designed with optimized line capacitance values to support chipsets with clock frequencies higher than 40MHz.

This structure has only a small effect on the rising and falling edges of the data signal, and there is almost no delay between the input and output of the device.

Using a maximum 2.8V, 1ns signal to simulate input Rt (10-90% rising edge) and Ft (10-90% falling edge), the results show that the delay caused by the filter (the difference between the output and input signals) No more than 1ns. It is certain that the data integrity will be completely maintained even for high-resolution LCD or camera applications.

Highly integrated solutions

Compared with discrete designs, the use of integrated EMI filters designed as flip-chip packages with stacked bumps can simplify PCB layout and save up to 80% of board area.

The results show that the line integration rate (PCB area / number of lines) is approximately 0.6. This means that these new filters can take up 0.6mm2 of PCB area per line to provide EMI functionality and ESD protection.

The new filter series is recommended to use 4, 6, and 8 "PI" line configurations to provide design flexibility and meet most high-speed data line design requirements. Its PCB area occupies 2.4mm2, 3.7mm2 and 5.0mm2, respectively, so it can almost completely use the traditional SOT323 plastic package.

Semiconductor's new low-capacitance EMI filters support 4, 6, and 8-wire configurations, and each configuration includes an RC filter network with Zener diodes on the side. A series resistance of 100 ohms and a line capacitance of 17 pF are used to achieve a minimum 30dB attenuation in the 0.8MHz to 2GHz range. The low capacitance of the devices means that they can be used in next-generation LCD displays and camera sensors with clock frequencies exceeding 40MHz.

 

If you want to know more, our website has product specifications for the EMI filters you can go to ALLICDATA ELECTRONICS LIMITED to get more information