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ES D1 8V U 1B and E SD 110 -B 1 TV S Diod es in TSL P a nd T S SL P BDTIC Tailor ed E SD P rot ec tion f or th e N FC Fron ten d Nea r Fi el d C o m mu nic atio n - Tec hnic al o ve r vie w - Fr ont en d E S D p ro tec tio n Applic atio n N ote A N 244 Revision: Rev. 1.2 2014-05-15 RF and P r otecti on D evic es www.BDTIC.com/infineon BDTIC Edition 2014-05-15 Published by Infineon Technologies AG 81726 Munich, Germany © 2014 Infineon Technologies AG All Rights Reserved. Legal Disclaimer The information given in this document shall in no event be regarded as a guarantee of conditions or characteristics. With respect to any examples or hints given herein, any typical values stated herein and/or any information regarding the application of the device, Infineon Technologies hereby disclaims any and all warranties and liabilities of any kind, including without limitation, warranties of non-infringement of intellectual property rights of any third party. Information For further information on technology, delivery terms and conditions and prices, please contact the nearest Infineon Technologies Office (www.infineon.com). Warnings Due to technical requirements, components may contain dangerous substances. For information on the types in question, please contact the nearest Infineon Technologies Office. Infineon Technologies components may be used in life-support devices or systems only with the express written approval of Infineon Technologies, if a failure of such components can reasonably be expected to cause the failure of that life-support device or system or to affect the safety or effectiveness of that device or system. Life support devices or systems are intended to be implanted in the human body or to support and/or maintain and sustain and/or protect human life. If they fail, it is reasonable to assume that the health of the user or other persons may be endangered. www.BDTIC.com/infineon ESD18VU1B and ESD110-B1 TVS Diodes in TSLP and TSSLP ESD Protection of the NFC Frontend Application Note AN244 Revision History: 2014-05-15 Previous Revision: prev. Rev. 1.1 Page Subjects (major changes since last revision) Adding ESD110-B1 BDTIC Trademarks of Infineon Technologies AG AURIX™, C166™, CanPAK™, CIPOS™, CIPURSE™, EconoPACK™, CoolMOS™, CoolSET™, CORECONTROL™, CROSSAVE™, DAVE™, EasyPIM™, EconoBRIDGE™, EconoDUAL™, EconoPIM™, EiceDRIVER™, eupec™, FCOS™, HITFET™, HybridPACK™, I²RF™, ISOFACE™, IsoPACK™, MIPAQ™, ModSTACK™, my-d™, NovalithIC™, OptiMOS™, ORIGA™, PRIMARION™, PrimePACK™, PrimeSTACK™, PRO-SIL™, PROFET™, RASIC™, ReverSave™, SatRIC™, SIEGET™, SINDRION™, SIPMOS™, SmartLEWIS™, SOLID FLASH™, TEMPFET™, thinQ!™, TRENCHSTOP™, TriCore™. Other Trademarks Advance Design System™ (ADS) of Agilent Technologies, AMBA™, ARM™, MULTI-ICE™, KEIL™, PRIMECELL™, REALVIEW™, THUMB™, µVision™ of ARM Limited, UK. AUTOSAR™ is licensed by AUTOSAR development partnership. Bluetooth™ of Bluetooth SIG Inc. CAT-iq™ of DECT Forum. COLOSSUS™, FirstGPS™ of Trimble Navigation Ltd. EMV™ of EMVCo, LLC (Visa Holdings Inc.). EPCOS™ of Epcos AG. FLEXGO™ of Microsoft Corporation. FlexRay™ is licensed by FlexRay Consortium. HYPERTERMINAL™ of Hilgraeve Incorporated. IEC™ of Commission Electrotechnique Internationale. IrDA™ of Infrared Data Association Corporation. ISO™ of INTERNATIONAL ORGANIZATION FOR STANDARDIZATION. MATLAB™ of MathWorks, Inc. MAXIM™ of Maxim Integrated Products, Inc. MICROTEC™, NUCLEUS™ of Mentor Graphics Corporation. Mifare™ of NXP. MIPI™ of MIPI Alliance, Inc. MIPS™ of MIPS Technologies, Inc., USA. muRata™ of MURATA MANUFACTURING CO., MICROWAVE OFFICE™ (MWO) of Applied Wave Research Inc., OmniVision™ of OmniVision Technologies, Inc. Openwave™ Openwave Systems Inc. RED HAT™ Red Hat, Inc. RFMD™ RF Micro Devices, Inc. SIRIUS™ of Sirius Satellite Radio Inc. SOLARIS™ of Sun Microsystems, Inc. SPANSION™ of Spansion LLC Ltd. Symbian™ of Symbian Software Limited. TAIYO YUDEN™ of Taiyo Yuden Co. TEAKLITE™ of CEVA, Inc. TEKTRONIX™ of Tektronix Inc. TOKO™ of TOKO KABUSHIKI KAISHA TA. UNIX™ of X/Open Company Limited. VERILOG™, PALLADIUM™ of Cadence Design Systems, Inc. VLYNQ™ of Texas Instruments Incorporated. VXWORKS™, WIND RIVER™ of WIND RIVER SYSTEMS, INC. ZETEX™ of Diodes Zetex Limited. Last Trademarks Update 2011-02-24 www.BDTIC.com/infineon Application Note AN244, Rev. 1.2 3 / 19 2014-05-15 ESD18VU1B and ESD110-B1 TVS Diodes in TSLP and TSSLP ESD Protection of the NFC Frontend List of Content, Figures and Tables Table of Content 1 Near Field communication - Overview ............................................................................................. 5 2 Current and future applications for NFC devices ........................................................................... 7 3 NFC implementation in the mobile phone ....................................................................................... 8 4 Requirements for proper NFC frontend ESD protection .............................................................. 10 5 Summary ........................................................................................................................................... 13 6 Appendix: TVS diode measurement results in real application .................................................. 14 7 Authors .............................................................................................................................................. 18 BDTIC List of Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 NFC Modules acting as tag/target (passive mode) or acting as initiator/reader (active mode). .......... 5 Time domain RF simulation of the NFC principle. ............................................................................... 6 RF envelope (13.56MHz) @ the primarty res., toggling the secondary res. lossless/lossy. ............... 6 NFC Modules both in active mode (e.g. in a P2P network) ................................................................. 7 Implementation of a NFC module in the mobile phone. ....................................................................... 8 Single ended NFC antenna frontend used in a mobile phone. ............................................................ 9 Differential NFC antenna frontend used in a mobile phone (lower EMI radiation). ............................. 9 Single ended and differential driven transforming EMI filter to reduce the harmonics and to increase the voltage swing across the resonant antenna circuit. .................................................................... 10 Correct application for a uni-directional TVS diode. ........................................................................... 10 Correct application for a Bi-directional TVS diode. ............................................................................ 11 TLP characteristic of an NFC TVS. .................................................................................................... 12 TLP measurement setup. ................................................................................................................... 13 Breakdown voltage and leakage current characterisation of ESD18VU1B and ESD110-B1 according to their data sheets. ........................................................................................................... 14 Breakdown voltage and leakage current characterisation of ESD18VU1B or ESD110-B1. Measurement condition: applied voltage is controlled, leakage current is measured. ...................... 14 Circuit structure of application related measurement setup for ESD18VU1B / ESD110-B1. ............ 15 Measurement setup according NFC FE for the ESD18VU1B / ESD110-B1. .................................... 15 Fundamental power H1 and harmonics power H2, H3 for various RF voltage @ TVS diode. .......... 16 Signal waveform direct at the TVS diode for various antenna voltage PART#1 Antenna voltage (Ch1), TVS diode current Ch2 (voltage @ 10 Ohm res) .................................................................... 16 Signal waveform direct at the TVS diode for various antenna voltage PART#2 Antenna voltage (Ch1), TVS diode current Ch2 (voltage @ 10 Ohm res) .................................................................... 17 www.BDTIC.com/infineon Application Note AN244, Rev. 1.2 4 / 19 2014-05-15 ESD18VU1B and ESD110-B1 TVS Diodes in TSLP and TSSLP ESD Protection of the NFC Frontend Near Field communication - Overview 1 Near Field communication - Overview Near Field Communication or NFC, is a short-range high frequency wireless communication technology which enables the exchange of data between devices over about a 10…20 centimeter distance. The technology is a simple extension of the ISO/IEC 14443 proximity-card standard (proximity card, RFID) that combines the interface of a smartcard and a reader into a single device. An NFC device can communicate with both existing ISO/IEC 14443 smartcards and readers, as well as with other NFC devices, and is thereby compatible with existing contactless infrastructure already in use for public transportation and payment. NFC is primarily aimed for usage in mobile phones. NFC communicates via magnetic field induction, where two loop antennas are located within each other's near field, forming an air-core transformer (figure 1, figure 2 and figure 4). It operates within the globally available and unlicensed radio frequency ISM band (Industrial, Scientific and Medical) of 13.56 MHz. BDTIC Working distance with compact standard antennas: up to 20 cm. Supported data rates: 106, 212, 424 kbit/s. Manchester coding with 10% ASK (Amplitude Shift Keying) modulation rate. Modified Miller coding with 100% ASK modulation rate. NFC device can work in passive mode (battery off) and in active mode: o card emulation: the NFC device behaves like an existing contactless card or RFID tag. The NFC device is passive and is triggered by an active initiator NO continous application, only active for a short time frame. o reader mode: the NFC device (initiator) is active and read a passive RFID tag, for example for interactive advertising. o P2P mode: two NFC devices are communicating together and exchanging information. Both NFC devices has to be in the active mode. Initiator/Reader Target/Tag L_sec secondary resonator 13.56MHz Reverse magnetic coupling bandpass Data from target/tag Forward magnetic coupling L_prim C_prim matched EMI filter primary resonator 13.56MHz C_sec amplifier ASK demodulator Figure 1 NFC Modules acting as tag/target (passive mode) or acting as initiator/reader (active mode). www.BDTIC.com/infineon Application Note AN244, Rev. 1.2 5 / 19 2014-05-15 ESD18VU1B and ESD110-B1 TVS Diodes in TSLP and TSSLP ESD Protection of the NFC Frontend Near Field communication - Overview 1.1 Passive Communication Mode The initiator device provides a magnetic carrier field and the NFC device (target) answers by modulating the existing magnetic field. In this mode, the target device creates its operating power from the initiator provided electromagnetic field, thus making the Target device a transponder. This mode is similar to the RFID (Radio Frequency Identification Device) working mode. The basic principle of this passive mode is the magnetic air coupling between Initiator´s (reader) primary coil L_prim and the the target coil L_sec on secondary side. Energy is transmitted from L_prim to L_sec and picked up on the secondary side (target) (forward response). On one hand the received magnetic energy is used to power the tag, on the other the received magnetic field is modulated. The tag is responding by modulating the Q-factor of the secondary resonance circuit L_sec/C_sec by switching on and off a shunt resistor according to the data sequence. This periodic attenuation of the secondary resonance circuit is visible on primary side (reverse response) and can be detected. The reverse response is reduced by reducing the coupling factor k, as a result of increasing the distance between the initiator (primary) and the target (secondary). BDTIC Figure 2 Time domain RF simulation of the NFC principle. RF Envelope @ primary side: Lossless secondary resonator Lossy secondary resonator Initiator / reader are very close here Coupling factor k=0.1 Figure 3 RF envelope (13.56MHz) @ the primarty res., toggling the secondary res. lossless/lossy. www.BDTIC.com/infineon Application Note AN244, Rev. 1.2 6 / 19 2014-05-15 ESD18VU1B and ESD110-B1 TVS Diodes in TSLP and TSSLP ESD Protection of the NFC Frontend Current and future applications for NFC devices 1.2 Active Communication Mode Running this mode the NFC device can act as an initiator (active reader) to get contact with a passive target. Two NFC devices can act as initiator and target device and communicate by alternately generating their own modulated field. A device deactivates its RF field while it is waiting for data. In this mode, both devices typically need to have a power supply. Initiator/Reader #1 Initiator/Reader #2 L_sec matched EMI filter primary resonator 13.56MHz C_sec Forward magnetic coupling L_prim C_prim matched EMI filter primary resonator 13.56MHz BDTIC Modulation input bandpass Data from #2 Reverse magnetic coupling Modulation input bandpass Data from #1 amplifier amplifier ASK demodulator ASK demodulator Figure 4 NFC Modules both in active mode (e.g. in a P2P network) 2 Current and future applications for NFC devices Plenty of applications are present in the market yet, or will enter the market soon. Mobile Commerce: o Mobile ticketing – for airplanes, for public transport, for concerts/events. o Mobile payment — the device acts as a debit/ credit payment card. o Electronic money – like a stored value card. Proof of Identity o Access control for buildings, or IT equipment. o Electronic keys - car keys, house/office keys, hotel room keys, etc. NFC can be used to configure and initiate other wireless network connections such as Bluetooth, Wi-Fi. The time consuming configuration procedure for identification to a Bluetooth or WiFi system is reduced by a ―one touch‖ of two mobiles equipped with NFC devices To provide the required security level for all these applications, the NFC modem is combined with a secure controller (NFC module). In a mobile phone the NFC module is also linked to the SIM card. www.BDTIC.com/infineon Application Note AN244, Rev. 1.2 7 / 19 2014-05-15 ESD18VU1B and ESD110-B1 TVS Diodes in TSLP and TSSLP ESD Protection of the NFC Frontend NFC implementation in the mobile phone 3 NFC implementation in the mobile phone To provide a highly secure environment especially for mobile commerce, the entire NFC communication has to be controlled by several security authorities. Therefore the NFC modem is linked to the SIM card and to the secure controller. Baseband ISO 7816 SIM Application Processor BDTIC SWP (ETSI) UART/I2C .… Secure Controller Figure 5 Phone in Reader Mode Active Card Emulation Passive – Battery Off NFC Modem Service Discovery P2P Implementation of a NFC module in the mobile phone. The signal generation and signal extraction is done completely in the NFC modem for the active mode as well as for the passive mode. The front-end of the NFC modem includes the mandatory transforming EMI filter and the magnetic loop antenna. This loop antenna inductor in combination with a capacitance provides the resonance circuit, tuned to 13.56 MHz. The resonance circuit on primary side (initiator/reader) is coupled to the resonance circuit of secondary side (NFC modem in passive mode, target/tag). Coupling factor ―k‖ is quite small and depends on the distance between reader and target. The inductors L_prim and L_sec on primary and secondary sides work as an air-coupled transformer with k<<1. The distance between primary and secondary side is within the nearfield of the magnetic field. There is no conversion from magnetic energy to electrical and back (farfield behavior). Because of the very small antenna in relation to the wavelength at 13.56 MHZ, the conversion from magnetic near field distribution in an electromagnetic far field distribution is very weak. This limits the range of an NFC system significant to < 20cm, even for special equipment to < 10m. For passive mode (battery off mode) of the NFC module the NFC module is powered by the magnetic field of the initiator/reader and modulates this information data by switching his 13.56 MHZ resonance circuit between lossless and lossy mode. The loss of energy in the secondary resonance circuit causes a feedback return to the primary resonance circuit and drops down the voltage slightly across the primary resonance circuit (figure 2, figure 3). This can be detected by an ASK demodulator and a logarithmic amplifier. For the active mode the NFC modem can work as a (initiator/reader) and collects data from a passive target/tag. To transmit data from one NFC module to another NFC module in a kind of peer to peer configuration, both NFC modules has to be in active mode and act as data transmitter and data receiver. In this case the TX signal is directly ASK modulated. www.BDTIC.com/infineon Application Note AN244, Rev. 1.2 8 / 19 2014-05-15 ESD18VU1B and ESD110-B1 TVS Diodes in TSLP and TSSLP ESD Protection of the NFC Frontend NFC implementation in the mobile phone In a mobile phone the NFC frontend is often separated into the TX driver with the EMC filter and RX signal decoupling and the high impedance 13.56 MHz resonator. The 13.56 MHz resonator includes the loop antenna (resonator´s inductance) and a parallel capacitor (resonator´s capacitance). Because of the loop antenna size, the 13.56 MHZ resonance circuit is located often in the bottom shell of the mobile, which can be removed by the user. An interface is generated inside the NFC frontend which then becomes ESD critical. A proper ESD protection becomes mandatory to protect the EMI filter and the driver of the NFC frontend, located on main mobile phone PCB. single ended antenna Main PCB / Top shell Interconnection top/bottom shell “external pads”? Bottom shell BDTIC RF=13.56MHz Vsignal vs. GND<+-18Vp Figure 6 loop GND EMI-LP filter Antenna matching RX I_res TX+ GND TVS diode bi-directional U_br ~18…19V Low cap.type!!! Linearity! Loopantenna ~1µH NFC Module TX/RX section TX+ Caps should be high voltage type to be save regards the residual ESD peak Single ended NFC antenna frontend used in a mobile phone. differential antenna Main PCB / Top shell Interconnection top/bottom shell “external pads”? RF=13.56MHz Vsignal vs. GND<+-18Vp +Vsignal vs. -Vsignal <36V!!! GND RX EMI-LP filter Antenna matching GND loopTVS diode bi-directional U_br ~18…19V Low cap.type!!! Linearity! I_res loop+ TX- Loopantenna ~1µH NFC Module TX/RX section TX+ Figure 7 Bottom shell Caps should be high voltage type to be save regards the residual ESD peak Differential NFC antenna frontend used in a mobile phone (lower EMI radiation). www.BDTIC.com/infineon Application Note AN244, Rev. 1.2 9 / 19 2014-05-15 ESD18VU1B and ESD110-B1 TVS Diodes in TSLP and TSSLP ESD Protection of the NFC Frontend Requirements for proper NFC frontend ESD protection Transforming EMI-LP-filter for single ended antenna matching TX+ Transforming EMI-LP-filter for differential antenna matching loop+ TX+ loop+ TXGND GND RX Figure 8 GND GND RX loop- Single ended and differential driven transforming EMI filter to reduce the harmonics and to increase the voltage swing across the resonant antenna circuit. BDTIC Besides the high impedance resonant loop antenna other antenna structures are possible. They might have different requirements for ESD protection. Please contact the local Infineon sales office for assistance. 4 Requirements for proper NFC frontend ESD protection In single ended and in differential driven antenna frontends, the RF signal (13.56 MHz) @ the resonator can be up to about +-18Vp vs. GND. Therefore the TVS diode has to be a so called bi-directional type, to be suitable for a wanted voltage swing of about +18Vp and for -18Vp. A uni-directional TVS diode would clip on negative voltage swings. In a single ended antenna frontend, the usable antenna voltage is defined at ―loop+‖ vs. ―GND‖ (e.g. +-18Vp). In a differential driven frontend, wanted antenna voltage at ―loop+‖ vs. ―loop-― can be e.g. +-36Vpp. Therefore the wanted antenna voltage in differential driven antenna frontends can be 2 times the antenna voltage of a single ended system. Furthermore the EMI radiation in a diff. Driven frontend is significant lower. 4.1 Uni-directional TVS diode vs. bi-directional TVS diode Uni-directional TVS diode: A uni-directional TVS diode is designed for a wanted signal between ~0V and ―maximum working voltage‖. The ESD protection capability is granted for a uni-directional diode for positive AND negative ESD strikes in the same way. Wanted signal positive voltage swing!! Vp < V_maximal working voltage shunts positive and negative ESD strike ~0V Blocks positive wanted signal < V_maximal working voltage Uni-directional TVS diode Figure 9 for negative wanted signal: signal is clipped Correct application for a uni-directional TVS diode. www.BDTIC.com/infineon Application Note AN244, Rev. 1.2 10 / 19 2014-05-15 ESD18VU1B and ESD110-B1 TVS Diodes in TSLP and TSSLP ESD Protection of the NFC Frontend Requirements for proper NFC frontend ESD protection Bi-directional TVS diode: A bi-directional TVS diode is designed for a wanted signal between ―negative maximum working voltage‖ and ―positive maximum working voltage‖. The ESD protection capability is granted for a bi-directional diode for positive AND negative ESD strikes in the same way. Wanted signal positive voltage swing!! +Vp < +V_maximal working voltage shunts positive and negative ESD strike ~0V Blocks negative wanted signal < - V_maximal working voltage BDTIC -Vp < -V_maximal working voltage Bi-directional TVS diode Blocks positive wanted signal < + V_maximal working voltage Figure 10 Correct application for a Bi-directional TVS diode. 4.2 Principles of the transforming EMI filter In the NFC system, the TX driver (low output impedance of some 10 Ohm) generates a differential 13.56 MHZ signal between 0V and may be 3V (~3V for a mobile phone application). The shape of this signal locks like a square wave. This 0V/3V signal is fed to a transforming EMC filter (figure 7). One job of the transforming EMC filter is to eliminate all harmonics to avoid interference with the GSM masterclock close to 27.12 MHZ. The other function is to shift up the NFC driver signal to a higher amplitude and impedance level. Impedance level is moving to about 1k Ohm or more and signal amplitude could become more than 10Vp or even higher at the resonant 13.56 MHZ antenna. 1) the transformation relation and 2) loss in the transforming EMI filter and in the 13.56 MHZ resonance circuit. But a strong impedance transformation ratio (to a high voltage swing at the antenna) makes the resonance circuit very narrowband and very sensitive to parasitic effects or capacitive hand-effect caused by the user. 4.3 ESD requirements Therefore ―maximum working voltage‖ of the TVS diode has to fit with the maximum peak voltage @ the 13.56 MHZ resonator. Below the ―maximum working voltage‖ / ―trigger voltage‖ the TVS diode is nearly a perfect ―open circuit‖ and is NOT clipping the signal. The leakage current is below the maximum leakage current specified for the TVS device. For optimized system ESD protection, the TVS diode´s breakdown voltage should fit to the maximal wanted signal in the circuit. Increasing the ―maximum working voltage‖ and inherently the ―minimal breakdown voltage‖ will cause a higher clamping voltage in case of an ESD event. This higher clamping voltage means a higher ESD stress for the EMC filter/NFC modem. So it is always a trade off between actual required ―maximum working voltage‖ and the desired ESD performance. Because the ―maximum working voltage‖ is fixed by application, ESD performance optimization is possible only by minimizing the dynamic resistance (R_dyn) of the TVS diode. The R_dyn is the switch on resistance of a TVS diode in case of an ESD event. R_dyn should be as small as possible to keep the residual clamping voltage as small as possible. Optimizing R_dyn requires wide experience in TVS diode development and semiconductor technique (figure 11). www.BDTIC.com/infineon Application Note AN244, Rev. 1.2 11 / 19 2014-05-15 ESD18VU1B and ESD110-B1 TVS Diodes in TSLP and TSSLP ESD Protection of the NFC Frontend Requirements for proper NFC frontend ESD protection 4.4 ESD protection in point of RF performance The ESD protection circuit should not create harmonic distortion to the 13.56 MHZ RF signal. Therefore the TVS diode has to be linear as much as possible. The TVS diode´s ―Maximum working voltage‖ has to be high enough to withstand the maximum peak voltage @ the 13.56 MHZ resonator without signal clipping. The bi-directional TVS diodes ESD18VU1B and ESD110-B1 with a trigger voltage of 20V (min. value) fit excellent into this application. In point of TVS diode capacitance, both ESD18VU1B and ESD110-B1 show outstanding 0.3pF (typical capacitance at 1MHz). 4.5 ESD performance in point of residual ESD stress The residual ESD voltage in case of an ESD strike depends on the TVS diode´s breakdown voltage and on the diodes´ ―switch on‖ resistance (R_dyn). The dynamic resistance (R_dyn) can be characterised by the TLP (Transmission Line Pulse), where we feed a short, well defind current pulse through the diode and measure the clamping voltage across the TVS diode. This clamping voltage is visible to the subsequent circuit and can still cause a residual ESD stress for the device. The R_dyn for both ESD18VU1B and ESD110-B1 is about 600 mOhm, which is state of the art in this application. BDTIC 30 NFC-TVS_TLP responce TLP Current 25 R_dyn: (U1-U2)/(I1-I2) 20 U1,I1 15 U_breakdown 10 Maximum working voltage 5 vvvoltagevolatge_brea kdown 0 0 Figure 11 5 10 15 U2,I2 20 25 TLP Voltage 30 35 40 TLP characteristic of an NFC TVS. www.BDTIC.com/infineon Application Note AN244, Rev. 1.2 12 / 19 2014-05-15 ESD18VU1B and ESD110-B1 TVS Diodes in TSLP and TSSLP ESD Protection of the NFC Frontend Summary 4.6 Attachment: TLP measurement overview Measuring TLP voltage accross the DUT V V(t) High Voltage Pulse Generator BDTIC t Measuring TLP current into the DUT 50 Ohm I(t) I I_TLP DUT V_TLP 50 Ohm TLP system TLP Current (A) t TLP pulse length can be from 30nsec to 500nsec (100nsec typ.) TLP pulse rise time can be adjusted from 100psec to 10nsec (300psec typ.) Sweeping the TLP current to get the high current I/V TVS diode characteristic I I , V V TLP Voltage (V) Figure 12 TLP measurement setup. 5 Summary ESD protection in the NFC frontend is easy to realize with application tailored TVS diodes. Numerous of basic conditions have to be addressed. The Infineon ESD18VU1B and ESD110-B1 are specifically developed for this application. ESD18VU1B and ESD110-B1 provide the right breakdown voltage in combination with a very low diode capacitance, which keeps the non-linear distortions very low. Package wise the ESD18VU1B and ESD110-B1 are available in leadless package, correlating to SMD (EIA) size 0402 (TSLP) and to SMD (EIA) size 0201 (TSSLP).The electrical parameters of these two diodes in data sheet are identical. www.BDTIC.com/infineon Application Note AN244, Rev. 1.2 13 / 19 2014-05-15 ESD18VU1B and ESD110-B1 TVS Diodes in TSLP and TSSLP ESD Protection of the NFC Frontend Appendix: TVS diode measurement results in real application 6 Appendix: TVS diode measurement results in real application 6.1 Breakdown voltage and leakage current characterisation of NFC TVS Diodes BDTIC Figure 13 Breakdown voltage and leakage current characterisation of ESD18VU1B and ESD110-B1 according to their data sheets. Current (A) NFC ESD18VU1B-02LS 1,00E+00 1,00E-01 1,00E-02 1,00E-03 1,00E-04 1,00E-05 1,00E-06 1,00E-07 1,00E-08 1,00E-09 1,00E-10 1,00E-11 1,00E-12 1,00E-13 1,00E-14 DC DCcharacteristic characteristicofofESD18VU1B NFC diode device device used usedfor for DC DCand andRF RFtests tests “trigger voltage” @ 1mA maximum reverse working voltage @ 30nA 0 1 2 3 4 5 6 7 8 V-Forced 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Voltage (V) Figure 14 Breakdown voltage and leakage current characterisation of ESD18VU1B or ESD110-B1. Measurement condition: applied voltage is controlled, leakage current is measured. According to the measurement shown above, the ESD18VU1B / ESD110-B1 diode remains in isolating mode till ~23.5V is reached. Breakdown voltage and trigger voltage are nearly the same (~23.5V) because of very steep skirt in I/V diagram. NFC communication is not a continuous working application. Data transmission in the NFC application is realized in a short timeframe, independently from the NFC module that is working in active mode (self powered by own battery) or in passive mode (external powered by the reader). www.BDTIC.com/infineon Application Note AN244, Rev. 1.2 14 / 19 2014-05-15 ESD18VU1B and ESD110-B1 TVS Diodes in TSLP and TSSLP ESD Protection of the NFC Frontend Appendix: TVS diode measurement results in real application 6.2 AC characteristic of the TVS diodes under NFC application conditions 50 Ohm RF Gen. Figure 15 resonant loop antenna Transforming EMI filter Z_load Circuit structure of application related measurement setup for ESD18VU1B / ESD110-B1. BDTIC ESD18VU1B or ESD110-B1 located in resonant NFC frontend antenna circuit, adjusted to 13.56 MHZ. Resonant NFC frontend antenna circuit driven by 50 Ohm signal generator and transforming EMI filter Antenna impedance about 1k Ohm RF Generator 50 Ohm Impedance transfoming low-pass filter + loop antenna Voltage divider 1:195 Z_load TVS Diode ESD18VU1B Spectrum analyzer 50 Ohm 4700 47 50 => 1k 10 Ch1 Oscilloscope Ch2 Figure 16 Measurement setup according NFC FE for the ESD18VU1B / ESD110-B1. To evaluate the AC (RF) characteristic of the ESD18VU1B / ESD110-B1, the TVS diode was characterized in the NFC like frontend. Breakdown / trigger voltage can be detected by measuring the nonlinearity products (harmonics) generated by the TVS diode. By exceeding the breakdown voltage of the TVS diode, the TVS diode starts to become conducting. This results in a kind of ―voltage depending‖ signal amplitude limitation. Signal peak is affected only, so the signal shape is changing (time domain). The RF voltage (~13.56MHz) across the TVS diode (and across the resonant antenna) is controlled by the power level of the 50 Ohm generator. All passive devices including the antenna inductance have to work in linear mode. In frequency domain the change of the sine-wave shape is visible by an increase of the harmonics, especially H3 (3 times the fundamental frequency) and H5 (5 times the fundamental frequency). We run the RF characterisation of ESD18VU1B / ESD110-B1 in: Frequency-Domain via spectrum analyser (SA). Time Domain via oscilloscope. www.BDTIC.com/infineon Application Note AN244, Rev. 1.2 15 / 19 2014-05-15 ESD18VU1B and ESD110-B1 TVS Diodes in TSLP and TSSLP ESD Protection of the NFC Frontend Appendix: TVS diode measurement results in real application 6.2.1 Frequency domain characterisation via spectrumanalyser (SA) RF measurements in frequency and time domain with TVS diode WITH TVS: Generator power P(H1) @ 13.56MHz P(H1_gen) = 23dBm generator (+-24.6Vp at antenna) P(H1_SA)= -8.0dBm P(H2_SA)= -69dBm P(H3_SA)= -50dBm P(H1_gen) = 22dBm generator (+-24.4Vp at antenna) P(H1_SA)= -8.1dBm P(H2_SA)= -77dBm P(H3_SA)= -55dBm P(H1_gen) = 21dBm generator (+-24.0Vp at antenna) P(H1_SA)= -8.2dBm P(H2_SA)= -77dBm P(H3_SA)= -72dBm P(H1_SA) = 20dBm generator (+-21.3Vp at antenna) P(H1_SA)= -9.2dBm P(H2_SA)= -80dBm P(H3_SA)= -83dBm BDTIC ―0.1dB‖ compression point @ ~+24.2Vp / -24.2Vp @ 21.4dBm gen. „Hard limiter― @ ~+-25Vp Figure 17 Fundamental power H1 and harmonics power H2, H3 for various RF voltage @ TVS diode. 6.2.2 Time domain characterisation via oscilloscope Linear RF Linear RF Ch1 Ch1 Ch2 Ch2 P_generator: 20dBm P_generator: 21.3dBm NON linearities starts NON linearities grows Ch1 Ch1 Ch2 Ch2 P_generator: 21.4dBm Figure 18 P_generator: 22dBm Signal waveform direct at the TVS diode for various antenna voltage Antenna voltage (Ch1), TVS diode current Ch2 (voltage @ 10 Ohm res) www.BDTIC.com/infineon Application Note AN244, Rev. 1.2 16 / 19 PART#1 2014-05-15 ESD18VU1B and ESD110-B1 TVS Diodes in TSLP and TSSLP ESD Protection of the NFC Frontend Appendix: TVS diode measurement results in real application NON linearities grows fast NON linearities become steady state Ch1 Ch1 Ch2 Ch2 P_generator: 23dBm P_generator: 24dBm BDTIC NON linearities become steady state Ch1 Ch2 P_generator: 25dBm Figure 19 Signal waveform direct at the TVS diode for various antenna voltage Antenna voltage (Ch1), TVS diode current Ch2 (voltage @ 10 Ohm res) PART#2 6.2.3 Comparing measurement in frequency- and time domain with DC results DC (leakage current and breakdown / trigger voltage characteristic) fits exactly with the RF characteristic of breakdown / trigger voltage evaluated by measuring harmonics and the signal shape. Harmonics starts to grow up, exceeding the breakdown- / trigger voltage. For RF (13.56MHz) fully linear characteristic up to ~+24Vp / -24Vp was measured. Exceeding the so called ―0.1dB‖ compression point @ ~ +24.2Vp / -24.2Vp the diode acts as a very smooth signal limiter. Breakdown voltage DC of ~ 23.5V, is very similar to the RF ―0.1dB‖ compression point @ ~ +24.2Vp / 24.2Vp. www.BDTIC.com/infineon Application Note AN244, Rev. 1.2 17 / 19 2014-05-15 ESD18VU1B and ESD110-B1 TVS Diodes in TSLP and TSSLP ESD Protection of the NFC Frontend Authors 7 Authors Alexander Glas Infineon Principal Engineer ―RF and Protection Devices‖. 8. References Infineon AG - Application Note AN210: « Effective ESD Protection Design at System Level using VF-TLP Characterization Methodology » BDTIC For data sheets and further documents please visit www.infineon.com/ESDprotection www.BDTIC.com/infineon Application Note AN244, Rev. 1.2 18 / 19 2014-05-15 BDTIC w w w . i n f i n e o n . c o m www.BDTIC.com/infineon Published by Infineon Technologies AG AN244