Miniature Filter Takes Aim at EMI

April 13, 2017

A new compact lowpass filter has been introduced to overcome interference.

Without question, electromagnetic-interference (EMI) is something that designers must be mindful of when designing circuits for wireless products. Proper filtering is key when it comes to overcoming potential EMI problems. Discrete capacitors and inductors are commonly used to suppress interference in communication frequency bands. However, TDK Corporation recently introduced a new integrated component that is intended to help designers defeat EMI: the MEM1005PP251T LC filter, intended for signal lines.

As mentioned, discrete capacitors and inductors are often used to suppress EMI. However, the MEM1005PP251T LC filter actually contains two capacitors and one inductor in a standard 0402 case size (Fig. 1). These elements together form a lowpass Pi filter. Taking advantage of the MEM1005PP251T therefore enables a designer to avoid building filters with discrete parts. Those who use this filter no longer have to be concerned about the performance of the individual components that are contained in a discrete-based design.

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1. This LC filter, available in a compact 0402 size, contains two capacitors and one inductor.

The small size of the MEM1005PP251T allows the required board space to be reduced by about 61% in comparison to using discrete components. This space reduction is significant in terms of meeting today’s smaller-size requirements. In particular, portable products demand high performance in small sizes.

The filter has a specified cutoff frequency of 250 MHz. Its specified insertion loss is 30 dB across a frequency range of 700 MHz to 3 GHz (Fig. 2). The company asserts that this insertion loss performance allows for well suppressed interference and increased reception sensitivity in the wireless communication frequency bands. Moreover, the MEM1005PP251T has a dc resistance of 0.8 Ω, which contributes to low-loss operation.

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2. This plot shows the filter’s typical insertion loss.

In addition, the MEM1005PP251T has a maximum rated voltage of 10 V and a maximum rated current of 350 mA. This rated current is 3.5 times greater than the maximum rated current of the company’s MEM1608P series, which is actually offered in a larger 0603 case size. Furthermore, the filter has an operating temperature range of –55°C to +125°C.

In terms of applications, the MEM1005PP251T is intended to be used in designs for products like smartphones, tablets, computers, cameras, and gaming consoles. Base stations represent another potential market. Volume production of the MEM1005PP251T has already begun. On a final note, TDK Corporation also has plans to expand the series to meet a wider range of requirements.

TDK Corporation