Electrostatic discharge (ESD) protection and electromagnetic interference (EMI) are becoming increasingly important considerations for all electrical equipment. Consumers are demanding more features and slim industrial designs in portable/wireless devices such as smartphones, requiring designers to pay more attention to ESD and EMI performance in small form factor packages. This article will analyze circuit protection requirements, compare different circuit protection technologies and filtering technologies, and introduce ON semiconductor‘s products for typical circuit protection and filtering applications, helping design engineers to design more reliable portable and consumer products.
Key Chipset ExternalESDProtection requirements
The industry is using state-of-the-art technology to manufacture advanced system-on-chip (SoC). Designers are continually reducing the minimum feature size of their chip designs in order to optimize functionality and chip size. But there is a corresponding price: as feature size decreases, devices are more susceptible to ESD damage. The design window left by today’s integrated circuits (ICs) for protection functions has been reduced. ESD protection must work in safe overvoltage and overcurrent regions. As the industry moves to manufacture more advanced ICs with smaller geometries and lower voltages, the safe operating area for ICs is shrinking.
The key to effective ESD protection is to limit the voltage during an ESD event to be within the safe voltage window for a given chipset. ESD protection products achieve effective ESD protection by providing a low-impedance current path to ground during ESD events; protection products for new integrated circuits require lower dynamic impedance (Rdyn) to avoid voltages that can cause damage.
As the design window for protection features shrinks, it becomes more important to choose an ESD protection product with low dynamic impedance to ensure that the clamping voltage does not exceed the safety protection window of the new chipset. Therefore, ESD protection product suppliers must provide information on the effectiveness of the protection product, not just the survival level of the protection product itself.
siliconESDProtection technology and passiveESDComparison of protection technologies
ON Semiconductor’s protection and filtering solutions are based on advanced silicon processes. In comparison, several other low-cost passive solutions use a combination of ceramic, ferrite, and multilayer varistor (MLV) materials. These types of devices have traditionally had poor ESD clamping performance. In some passive solutions, downstream devices will experience voltages one or more orders of magnitude higher than the ON Semiconductor silicon solution, as shown in the ESD screenshot below, which compares the ON Semiconductor silicon solution to competing technologies in Performance under 8 kV ESD stress conditions. The turn-on voltage of the competing technology is so high that it will not activate at all, the voltage measured is nothing more than the voltage drop across the 50 Ω measurement circuit. Some other older technologies degrade even after a few ESD strikes. Due to the material composition, some passive devices tend to perform inconsistently at different temperatures and therefore have lower reliability in harsh environments.
picture1: Comparison of ESD Clamping Performance of ON Semiconductor Silicon Devices and Passive Competitors Measured at 8 kV in a 50 Ω System
Eliminate signal integrity issuesPicoGuard® XS ESDprotection technology
Traditional ESD protection products are mounted between signal traces and ground without interruptions on the signal path. To minimize the degradation of signal integrity on high-speed data lines, capacitance must be minimized, as shown in Figure 2.
picture2: Comparison of traditional ESD protection design methods with PicoGuard XS.
ON Semiconductor’s superior PicoGuard XS technology eliminates signal integrity issues by providing an impedance-matched signal path through the protection product. PicoGuard XS technology balances package series inductance with protection Diode capacitance to provide an excellent 100 Ω signal path that matches the impedance of traces on the PCB. In addition, this design virtually eliminates the need for inductance in series with the protection diode, thereby minimizing package-induced voltage spikes at the onset of an ESD event.
electromagnetic interference(EMI)Filtering: single-ended and common mode filters(CMF)
ON Semiconductor offers two types of EMI filters, single-ended filters and common mode filters. Single-ended filters are fabricated in different array configurations for parallel interfaces. These filters include general-purpose resistor-capacitor (RC) filters for low-speed signals such as audio, and Inductor-capacitor (LC) filters for higher-speed and power-sensitive interfaces. Low-pass filters provide cutoff frequencies ranging from 700 MHz to up to 6 GHz. The cutoff frequency is shown in the S21 diagram shown in FIG. 8 . Single-ended filters cannot meet the needs of high-speed differential interfaces.Differential interfaces have inherent noise immunity, but they are not completely immune to possibleAtThe effects of common-mode noise from external sources also do not prevent interface signals from radiating to other components of the system.
picture3: Single-ended low-pass filter characteristics
Common-mode filters (CMFs) can be used in these applications to remove unwanted common-mode noise and prevent high-speed signals from radiating unwanted common-mode noise signals to other system components. At the same time, the CMF also allows the desired high-speed data to pass virtually unaffected. A typical CMF characteristic is shown in Figure 4, which shows that common mode noise is eliminated while allowing differential mode signals to pass through without loss.
Figure 4: Common mode filter characteristics
Examples of circuit protection and filtering applications in portable and consumer products such as smartphones
1) USB 2.0Interface filtering and protection
ON Semiconductor provides low-capacitance ESD protection solutions suitable for 1 pair of high-speed lines and VCC for USB 2.0 interfaces (such as NUP4114UPX, NUP4114UCL, NUP4114H, ESD7L5.0 and ESD9L5.0), and also provides a common mode suitable for 1 pair of high-speed lines and VCC Filter and ESD protection solution (EMI2121) for USB 2.0 interfaces in portable/wireless products such as smartphones and digital cameras.
2) USB 3.0interfaceESDProtect
Portable/wireless devices such as smart phones and tablet computers have more and more functions, stronger performance, and larger storage capacity, and the demand for data communication with the outside world is also increasing. The USB standards-setting body announced that USB 3.0 ports, which are ten times faster than USB 2.0, are expected to support smartphone and tablet devices in 2012 or early 2013.
ON Semiconductor offers a range of solutions for USB 3.0 interfaces to provide low capacitance ESD protection for 2 pairs of SuperSpeed lines, 1 pair of High Speed lines and VCC. These solutions include ESD7008 (protect 8 lines, 0.12 pF capacitor, 5.5 x 1.5 mm UDFN-18 package), ESD7104 (protect 4 lines, 0.3 pF capacitor, 2.5 x 1.0 mm UDFN-10 package), ESD7004 (protect 4 lines line, 0.4 pF capacitor, 2.5 x 1.0 mm UDFN-10 package) and ESD7L (protects 2 lines, 0.5 pF capacitor, 1.2 x 1.2 mm SOT-723 package).
3) Camera and Display parallel interface and serial interface protection
ON Semiconductor provides protection solutions for parallel and serial interfaces of cameras and displays. Among them, low-pass filters and ESD protection solutions suitable for 4 to 12 line parallel interfaces include EMI720x series, EMI940x series, CM1693 series and CM1457 series; common mode filters and ESD protection solutions suitable for 3 to 5 pairs of high-speed serial channels Including EMI4182 and EMI4183, etc. These products can be used in applications such as smartphones and digital cameras.
4) Portable ProductsHDMIPort filtering and protection
Some smartphone and tablet designs have begun to support HDMI ports to meet the needs of users to transmit audio and video data at higher rates. ON Semiconductor provides low-impedance common mode filters (CMFs) suitable for filtering and protecting HDMI ports in portable products, suitable for low-capacitance ESD protection and common mode filtering for 4 pairs of high-speed lines and up to 6 additional interface lines.
5) consumer productsHDMIand Display port protection
ON Semiconductor provides different types of filtering and protection solutions for consumer HDMI and display ports, including low capacitance ESD protection for 4 pairs of high-speed lines, up to 6 additional lines, and common mode filtering solutions (EMI4182) for 4 pairs High-speed lines, low-capacitance ESD protection scheme for up to 6 additional lines (ESD7004, MG2040), and ESD protection PicoGuard® XS for 4 pairs of high-speed lines, up to 6 additional lines, internal impedance matching.
6) Audio filtering and protection for applications such as smartphones
ON Semiconductor provides corresponding EMI filters and ESD protection solutions for speakers/headphones, differential microphones, dual microphones and other applications, including NUF2441FC and NUF2450MU for speaker/headphone filtering and protection, as well as differential/dual microphone filtering and protection. CM6200 and CM6205 etc.
Summarize:
Designers need to select suitable circuit protection and filtering solutions for portable and wireless, consumer applications such as smartphones, tablets, and digital cameras. As the premier supplier of high-performance silicon solutions for energy-efficient electronics, ON Semiconductor is committed to providing protection and filtering solutions with the best technical and economic value for target applications. This paper analyzes the technical trend of circuit protection and the comparison of EMI filtering technology, and introduces the corresponding products of ON Semiconductor combined with specific application examples to help designers choose appropriate circuit protection and filtering solutions.
References:
1. ON Semiconductor’s circuit protection application webpage, www.onsemi.cn/PowerSolutions/content.do?id=16007
2. “Circuit Protection Scheme” brochure, www.onsemi.cn/pub/Collateral/BRD8080CN.rev1.pdf
3. “Circuit Protection Solutions Brochure”, www.onsemi.cn/pub/Collateral/BRD8080-D.PDF
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