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EMI Issues and Solutions for the Next Generation Smartphone2014/03/24

 

Due to the quick rotating steps of new technology revolutions, mobile phones have become a neccesity of human being daily lives. Particularly, the functional improvements and revolutions on smartphones are especially impressive. The feature of a smartphone nowadays is not only for telephoning and texting, but also a portible computer, a filming digital video, and a GPS. The new features of a smartphone include
  • The touch panel, as a friendly user interface
  • Global positioning system (GPS), to locate the position of the phone owner -- for guiding the traffic traveling, or helping for accident rescue.
  • Sending/recieving e-mails, which is an sincere, attractive, and undeniable feature for business people. It allows the business people not to carry a relatively heavy notebook computer all the time, just in case they might need the computer to send important and urgent e-mails.
  •  High resolution camera & film recording, which can replace a digital camera or video camera, so that the user can simply take a smartphone for phone calls, photo shooting, and taking short films.
  •  Video telephone conversation, which allow two persons to talk face-to-face on the phone call, although they are not at the same location when talking.
  •  Projection presentation, to allow business people to present their products at the customer site, no need to prepare a projector for presentation any more.
  • cloud computing (ex.: Apple iCloud), which let the end user to access the same file anywhere there is internet service, instead of taking a hard disk or USB flash drive at any time anywhere.
  • Application JAVA program download (ex.: App store), which let the user to keep upgrading his smartphone.
  • Personal digital assistant (PDA), including alarm clock, scheduling notebook, calculator, dictionary, phone book, map.entertainments, which include games, music/film player, ...etc. facilities, which could be ringback tone, headset, ...
After briefly introduce the powerful features of smartphones, it would be easy to understand that the hardwares of each modules in the smartphone would necessarily take the very advanced technologies, so that the amazing features would be well performed by endcustomers. Therefore, the smartphone processor unit makers are expected to develope their products with faster operation speed, better performance, more powerful, and more impressive features than ever. That's why the processor technologies have been upgraded from single-core to dual-core, then, even upgraded to quad-core (Snapdragon S4) which has just been released in Oct. of 2011.With the powerful processor as the brain of a smartphone, it is also required to have a high desity and large capacity of ROM (ready only memory), RAM (random access memory) and even flash memory, so that the smartphone can support the large amount of data transfering, ex. system information, application programs, and multimedia data.
 
Due to all the newest technologies/features are designed within a very limited small volume of a smartphone set, the integration density of the smartphone PCB (printed circuit board) layout is getting dramatically high, which forces the size of each device on the PCB is getting smaller, and, of course, the line-to-line spacing of PCB interconnect traces and the spacing between devices are also shrinked seriously. When the endcustomer turns on more functions/features, there would be more turned-on devices, which are all located very close to each other on the PCB of a smartphone set. These operating devices would generate signals to perform the functions that the endcustomer expects. However, the generated signals are all electronic noises to each other signal, which would interference and degrade each other functional performacnce that the endcustomer wants. More functions the endcustomer turns on, there would be more different kinds of signals surround the PCB inside the smartphone. Therefore, more worse EMI (electromagnetic interference) noises would be created even in the form of high-frequency harmonics. More worse, the 3C products (or, computers/communications/ consumer electronic products) are widely used for modern lives. The electronic signals generated by all these 3C products also become the EMI noises of each other 3C products. These EMI noises raise up the background noise level (or, amplitude) of the operating smartphone, which also degrades the functional performances of the smartphone.
 
To eliminate the mentioned EMI noises of smartphone sets, Amazing Microelectronic Corp. (also known as AMC, URL: www.amazingic.com) provides various kinds of EMI filter products for the smartphone makers to overcome this getting worse issue. Actually, Amazing Microelectronic Corp. has a very experienced working team for ESD (electrostatic discharge) technologies, and has already owned a lot of ESD related patents. All the EMI filter related products of Amazing Microelectronic Corp. are developed with very good ESD performances for the needs of smartphone makers when they develope their hardware designs. So that the smartphone makers can solve the EMI and ESD issues at the same time by simply taking the given solutions provided by Amazing Microelectronic Corp. The given EMI+ESD filter solutions are all designed in p-model (pi-model) LPF (low pass filter). Fig.1 shows the schematic circuit diagram of the p-model LPF. EMI+ESD filter products are generally mounted at the input/output ports of the electronic products. Therefore, the line capacitors (Cline) of the EMI+ESD filter products would be designed with TVS (transient voltage suppressor) devices for the ESD protection of the ESD current discharging from the input/output ports to GND (the ground plan). So that the EMI+ESD filter products can sustain good ESD immunities/performances.
Fig.1 The schematic circuit diagram of one channel of the EMI+ESD filter series prodcuts specially designed for smartphone applications by Amazing Microelectronic Corp.

 

For the smartphone applications, Amazing Microelectronic Corp. provides different EMI+ESD products for the following modules.
  • LCD (Liquid Crystal Display)
  •  SIM (subscriber identity module, SIM) card
  • Keypad
  • MMC card / SD card (multimedia card / secure digital card): the MMC card technologies are graduately replaced by SD card technologies. Due to that the MMC card still can be compatibly read by the SD card reader, the MMC card still has its market share [3].
  •  USB (universal serial bus): used for smartphone battery charger and data read/write
 
Table.1 The EMI+ESD filter product list developed by Amazing Microelectronic Corp.
Application for Different I/O Ports
Part Numbers in DFN Package
LCD
AZM-LCD04-06F, AZM-LCD05-0xF *
SIM
AZM-SIM01-03F
Keypad
AZM-KEY01-04F
MMC/SD card
AZM-MMC01-06F
USB
AZM-USB02-02F

* 'x' means different numbers, please contact with AMC sales for details.

 

For LCD module applications, Amazing Microelectronic Corp. also provide EMI+ESD products in CSP package for customers' different needs. The corresponding part numbers are: AZM-LCD01-04B, AZM-LCD02-08B, AZM-LCD03-10B, and AZM-LCDL1-10B.
 
The advantages of the EMI+ESD prodcuts developed by Amazing Microelectronic Corp. are listed as below.
1. Good ESD performance with much lower Vclamp (clamping voltage):
The ESD Vclamp of the EMI+ESD filter products is designed to be very low comparing with the other similar products of worldwide competitors.
When an ESD event appears to the protected PCB I/O ports, the EMI+ESD filter with lower ESD Vclamp can be triggered on earlier to protect the circuits and devices near the PCB I/O ports. On the other hand, if the Vclamp of an EMI/ESD filter is higher, it would need more ESD energy to trigger it on. This means that the circuits and devices near the I/O ports would have to sustain the ESD energy by themselves before the EMI/ESD filter being turned-on. Unfortunately, this would generally lead to the ESD damages on the circuits or devices near the I/O ports.
Fig.2 shows the Vclamp comparison curves measured by TLP (transmission line pulsing) system. The blue line is the characteristic of the EMI+ESD filter provided by Amazing Microelectronic Corp., and the pink line is characteristic of competitor's EMI+ESD filter. From Fig.2(a), it is clear that the Vclamp (x-axis) of the blue line (AMC's filter in DFN package) is about 8V, which is much lower than the Vclamp of the pink line (about 17.5V)(competitor's filter) at the current amplitude (y-axis) of 17A. Fig.2(b) shows the Vclamp characteristic comparison results for EMI+ESD filter products in CSP package. It is also clear that the Vclamp of the AMC's filter (blue line) is much lower than the Vclamp of the other competitors' filters (green and pink lines).
Therefore, we can know that the EMI+ESD filter provided by Amazing Microelectronic Corp. has much better ESD performance than the competitor's product, and can provide an efficient bypass path for the energy of an ESD event.
 

                                                                                                                                 (a) EMI filters in DFN package      

 

                                                 (b) EMI filters in CSP package
Fig.2 The Vclamp comparison curves measured by TLP (transmission line pulsing) system.
 
2. Can sustain over 15kV system-level ESD immunity (IEC 61000-4-2, contact mode ±15kV):
According to the specification of the IEC 61000-4-2 standard level-4 test, electronic products should pass 8kV ESD energy in contact discharge mode, and 15kV ESD energy in air discharge mode. The EMI+ESD filter products of Amazing Microelectronic Corp. can sustain over 15kV ESD energy in contact discharge mode, which is much higher than the EC 61000-4-2 specification.
 
3. Low standby power consumption, good for protable devices:
Smartphone is a portable consumer product, and its electrical power is provided by the embedded battery. Therefore, if the standby leakage current of the EMI+ESD filter is higher, then, the energy stored in the embedded battery would be consumed more quickly. This means that the power of the battery can only be used for a shorter period of time. This is kind of troublesome for the smartphone endcustomer.
Fig.3 shows the standby leakage current comparison curves. The blue curve is the DC I-V curve of AMC's EMI+ESD filter products, and the pink curve is the one of competitor's products. From Fig.3, it is clear that the leakage current (in y-axis) of the blue line is smaller than the one of the pink curve at around 6.5V (in x-axis). Hence, we can know that the AMC's EMI+ESD filter would consume less standby power from the embedded battery of a smartphone set. The endcustomer would not need to charge the embedded battery for a longer period of time.
Fig.3 Comparison of leakage current amplitudes from the I/O Port to the GND plane.
(AMC's product vs. some competitor's product)
 
4. Package type:
AMC's EMI+ESD filter products are designed with 2 kinds of package types. One is DFN (dual flat no-lead) package with pin-pitch of 0.4mm or 0.5mm. The other is CSP (chip scale package) package with pin-pitch of 0.4mm. Therefore, the occupied PCB layout area of any of AMC's EMI+ESD filter products is quite small, and is convenience for the device placement and circuit design of the smartphone PCB design.
 
To know more about the detail specifications of the EMI+ESD filter products, please contact with the Sales Department of Amazing Microelectronic Corp.: sales@amazingic.com .
Author: James Peng, Manager / R&D Dept. of AMC
 
 
References:
1.    Wikipedia, "智慧型手機," Oct. 9, 2011.
webpage :
2.    Qualcomm (NASDAQ: QCOM), "Snapdragon S4 Processors: System on Chip Solutions for a New Mobile Age," Oct. 7, 2011.
webpage :
3.    Wikipedia, "多媒體記憶卡," Jul. 30, 2011.
webpage :

     

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