Portable Product EMI Filtering Solutions

Driven by fierce competition among brands, portable electronic products are becoming more diversified and complex in terms of their functions. Due to their small size, higher and higher operating frequency, and lower and lower operating voltage, the electromagnetic signals generated by various functional modules interfere with each other more and more seriously in a very small volume. On the other hand, with the increasing popularity of various electronic products (including commercial and industrial use), for users of portable electronic products, the number of electronic products in operation and use around them is getting higher and higher, and the accumulated electromagnetic radiation interference generated by these electronic products is becoming more and more serious, making the electromagnetic interference ( EMI ) problem increasingly complex and serious.

The technical team of Amazing Microelectronics has accumulated rich technology and experience in electrostatic discharge ( ESD ) protection technology. The company's EMI filter products are mainly developed to solve the EMI problem when designing and developing hardware for portable electronic products. In order to effectively solve the EMI problem and take into account the function of ESD protection, Amazing Microelectronics has successively launched several EMI filters with ESD protection function. These EMI filter products are all pi-model low-pass filters (LPF). Since EMI filters are mostly used in the input and output ports of electronic products, the capacitors of the input and output terminals to the ground (GND or VSS) in the filter architecture are generally ESD protection components using transient voltage suppressors (TVS) to take into account high standards of ESD protection. In this way, in addition to providing a good low-pass filtering effect, it also has a good ESD protection effect.

Mobile phones are one of the most popular portable electronic products in recent years. In every mobile phone, there must be at least one SIM (Subscriber Identity Module) card for user identification and data storage. In the new smart phones, regardless of the brand, most of them have MMC (Multimedia Card) / SD (Secure Digital Storage) card for the storage of data such as camera, phone book, e-mail or short message.

Under normal use, when the mobile phone SIM card or MMC/SD card is transmitting data, when the harmonic radiation signal of the basic frequency (referred to as base frequency) of its transmission signal appears within the communication frequency band of the mobile phone, it will cause a certain degree of interference to the mobile phone's radio frequency communication signal.

On the contrary, the radiation generated by the mobile phone's radio frequency communication signal will also couple into the data transmission signal of the SIM card or MMC/SD card, causing distortion of the signal waveform. In serious cases, it will lead to data transmission errors.

For the two applications of SIM card and MMC/SD card, Jingyan Technology provides the corresponding electromagnetic interference filters AZM-SIM01-03F and AZM-MMC01-06F, which can solve the above electromagnetic interference problems. Table 1 shows the basic characteristic parameter values ​​of Jingyan Technology's AZM-SIM01-03F and AZM-MMC01-06F electromagnetic interference filter products. Both electromagnetic interference filters are suitable for circuit systems with a rated voltage of 5V or below, and the line capacitance values ​​are 22pF and 24.5pF respectively. When the operating frequency is 1GHz, the insertion loss can reach -20dB and -21.5dB respectively, which can significantly reduce the electromagnetic interference signal strength to less than one tenth to maintain the normal operation function of the protected circuit.

Basic characteristic parameter values ​​of electromagnetic interference filter products

In terms of electrostatic discharge protection, the transient voltage suppressors in this series of products have extremely low clamping voltages. The anti-static protection effect of AZM-MMC01-06F can be as high as 10kV or more (IEC 61000-4-2, contact mode ±10kV), and the anti-static protection effect of AZM-SIM01-03F can be as high as 15kV or more (IEC61000-4-2, contact mode ±15kV).

When an electrostatic discharge (ESD) event occurs, the lower the clamping voltage of the transient voltage suppressor, the more immediately it can conduct a considerable electrostatic discharge current, so that the protected circuit is protected from permanent damage and failure due to electrostatic discharge. Figure 1 shows the clamping voltage diagram of the AZM-SIM01-03F and AZM-MMC01-06F products measured using the transmission line pulse generation system (TLP). It can be clearly seen from the figure that the clamping voltage of these two electromagnetic interference filters is lower than 8.5V when the transmission line pulse generation system outputs a high electrostatic discharge current of 17A, which can effectively provide a fast and effective electrostatic discharge bypass path for the protected circuit.

Figure 1: AZM-SIM01-03F and AZM-MMC01-06F EMI filters: The clamping voltage at 17A is less than 8.5V

In addition, according to the specifications set by the IEC 61000-4-2 standard, the fourth level protection must provide at least 8kV in contact discharge mode and 15kV in air discharge mode. This series of products provides more than 10kV in contact discharge mode, which significantly exceeds the required value specified in the fourth level of the IEC 61000-4-2 standard.

Since portable devices rely on batteries to supply the required power, when the components are in normal use, the greater the leakage current, the greater the battery power consumption and the shorter the power supply time. Figure 2 shows the current-voltage (IV) characteristic curve of the new AZM-SIM01-03F and AZM-MMC01-06F electromagnetic interference filter products launched by JASON Technology. As can be seen from the curve in the figure, the leakage current of the new electromagnetic interference filter products is much less than 1uA at the applicable system operating voltage (here 5V or below 5V), so the sustainable use time of the battery of portable devices can be extended.

Figure 2: AZM-SIM01-03F and AZM-MMC01-06F EMI filters: The DC leakage current values ​​measured from the I/O terminal to ground (GND or VSS) are much less than 1uA

In terms of packaging, this series of products from Jingyan Technology uses a rectangular flat no-lead package (DFN) with a pin pitch of 0.4mm. Therefore, when designing a system, it can effectively reduce the circuit board area occupied by the electromagnetic interference filter components, facilitate the design of other circuit components, and easily rework the welding. When performing surface mounting of components, it is not easy to cause component damage.