B GA 7 2 8 L 7 Bro a d b a n d L o w No i s e A m p l i fi e r f o r FM R a d i o Ap p l i c a ti o n s u s i n g B GA 7 2 8 L 7 In c l u d i n g a c o n f i g u r a ti o n fo r mi n i mu m NF a n d o n e fo r b e s t i n p u t ma tc h i n g i n a 5 0 Oh m s ys te m Ap p l i c a ti o n N o te A N 2 3 1 Revision: Rev. 1.0 2010-08-02 RF a n d P r o te c ti o n D e vi c e s Edition 2010-08-02 Published by Infineon Technologies AG 81726 Munich, Germany © 2010 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. BGA728L7 BGA728L7 as a LNA for FM Radio Application Note AN231 Revision History: 2010-08-02 Previous Revision: prev. Rev. x.x Page Subjects (major changes since last revision) Trademarks of Infineon Technologies AG A-GOLD™, BlueMoon™, COMNEON™, CONVERGATE™, COSIC™, C166™, CROSSAVE™, CanPAK™, CIPOS™, CoolMOS™, CoolSET™, CONVERPATH™, CORECONTROL™, DAVE™, DUALFALC™, DUSLIC™, EasyPIM™, EconoBRIDGE™, EconoDUAL™, EconoPACK™, EconoPIM™, E-GOLD™, EiceDRIVER™, EUPEC™, ELIC™, EPIC™, FALC™, FCOS™, FLEXISLIC™, GEMINAX™, GOLDMOS™, HITFET™, HybridPACK™, INCA™, ISAC™, ISOFACE™, IsoPACK™, IWORX™, M-GOLD™, MIPAQ™, ModSTACK™, MUSLIC™, my-d™, NovalithIC™, OCTALFALC™, OCTAT™, OmniTune™, OmniVia™, OptiMOS™, OPTIVERSE™, ORIGA™, PROFET™, PRO-SIL™, PrimePACK™, QUADFALC™, RASIC™, ReverSave™, SatRIC™, SCEPTRE™, SCOUT™, S-GOLD™, SensoNor™, SEROCCO™, SICOFI™, SIEGET™, SINDRION™, SLIC™, SMARTi™, SmartLEWIS™, SMINT™, SOCRATES™, TEMPFET™, thinQ!™, TrueNTRY™, TriCore™, TRENCHSTOP™, VINAX™, VINETIC™, VIONTIC™, WildPass™, X-GOLD™, XMM™, X-PMU™, XPOSYS™, XWAY™. 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Last Trademarks Update 2009-10-19 Application Note AN231, Rev. 1.0 3 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio List of Content, Figures and Tables Table of Contents List of Figures ........................................................................................................................................................ 4 1 Introduction ........................................................................................................................................ 6 2 Overview ............................................................................................................................................. 7 3 3.1 3.2 3.3 Circuit optimized for Noise Figure ................................................................................................... 8 Summary of Measurement Results ...................................................................................................... 8 Schematic Diagram .............................................................................................................................. 9 Measured Graphs............................................................................................................................... 10 4 4.1 4.2 4.3 Circuit optimized for input matching ............................................................................................. 16 Summary of Measurement Results .................................................................................................... 16 Schematic Diagram ............................................................................................................................ 17 Measured Graphs............................................................................................................................... 18 5 Evaluation Board .............................................................................................................................. 24 Appendix 1: ESD protection circuit for system level ESD robustness .......................................................... 25 Authors 27 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 Figure 20 Figure 21 Figure 22 Figure 23 Figure 24 Figure 25 Figure 26 Figure 27 Figure 28 Figure 29 Figure 30 FM Radio RF front-end block diagram ................................................................................................. 6 Schematic diagram for minimum NF. ................................................................................................... 9 Insertion power gain at minimum NF. ................................................................................................ 10 Noise figure at minimum NF............................................................................................................... 10 Out-of-band Gain at minimum NF ...................................................................................................... 11 Input matching at minimum NF. ......................................................................................................... 11 Output matching of at minimum NF. .................................................................................................. 12 Reverse isolation at minimum NF. ..................................................................................................... 12 Input P1dB compression point at minimum NF.................................................................................. 13 Stability factor K at minimum NF. ....................................................................................................... 13 Stability factor µ1 and µ2 at minimum NF. ......................................................................................... 14 rd Output 3 order intermodulation distortion at minimum NF. .............................................................. 14 Input and Output impedance at minimum NF. ................................................................................... 15 Schematic diagram for best input matching. ...................................................................................... 17 Insertion Power Gain with best input matching .................................................................................. 18 Noise figure with best input matching ................................................................................................ 18 Out-of-Band attenuation with best input matching ............................................................................. 19 Input matching with best input matching ............................................................................................ 19 Output Matching with best input matching ......................................................................................... 20 Reverse Isolation with best input matching ........................................................................................ 20 Input 1dB ompression point with best input matching........................................................................ 21 Stability factor K with best input matching. ........................................................................................ 21 Stability factor µ1 and µ2 of with best input matching ........................................................................ 22 rd Output 3 order intermodulation distortion with best input matching ................................................. 22 Input and Output impedance with best input matching. ..................................................................... 23 Picture of Evaluation Board ................................................................................................................ 24 PCB Layer Information ....................................................................................................................... 24 ESD test pulse according to system level specification IEC61000-4-2 – Contact Discharge 15kV .. 25 Smart 2-step ESD protection approach based on external and internal ESD protection structure ... 26 Standard ESD protection topology with optional ESD resistor, blocking capacitor and a serial inductor ............................................................................................................................................... 26 Application Note AN231, Rev. 1.0 4 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio List of Content, Figures and Tables List of Tables Table 1 Table 2 Table 3 Table 4 Table 5 Comparison of the two circuits. ............................................................................................................ 7 Performance with min. NF at Vcc=Von=2.8 V, Vgs=0V ....................................................................... 8 Bill-of-Materials for minimum NF .......................................................................................................... 9 Performance with best input matching at Vcc=Von=2.8 V, Vgs=0V .................................................. 16 Bill-of-Materials for best input matching ............................................................................................. 17 Application Note AN231, Rev. 1.0 5 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Introduction 1 Introduction FM Radio has a long history to its credit starting from its development in 1933. Today, FM radio is an integral part of almost all mobile phones, including the ultra low cost phones. FM Radio broadcast today is not just used to listento songs and news, but also used for RDS (Radio Data System) to receive various services including TMC (Traffic Message Channel) which gives traffic information for navigation purposes. In addition, some handsets are being equipped with FM Radio transimission capability to send voice signals to car audio systems or Hi-Fi systems. Therefore, FM system design in a phone is getting more and more complex. Till recently, the headset served as the antenna for FM Radio reception, wherein the antenna size is a bit relaxed and the antenna performance is satisfactory. A new trend has emerged to be able to use FM radio also without the headset, wherein the antenna embedded into the phone. But in this case, the space constraint poses a challenge on the antenna design. Shrinking the size of the antenna reduces antenna gain and bandwidth, which introduces a high loss into the system which deteriorates the receiver performance, namely the receiver sensitivity. This application note presents Infineon solution to the aforementioned challenges leading to the design of a high performance RF front end with the lowest power consumption. A general topology for the RF front-end of FM Radio is as shown in Figure 1. Variations of the given application schematic are possible based on the complete system design and concept. These may include systems with only external headset antenna, only internal embedded antenna or both antennas co-existing. Infineon offers the complete chain of RF front-end parts between the antenna and the receiver IC for FM Radio, which include ESD protection devices, RF switches and LNAs. The focus of this application note is Low Noise Amplifier for FMR. Figure 1 FM Radio RF front-end block diagram An ESD protection circuit is needed at the antenna to protect the front-end system from ESD strikes, as the antenna is susceptible to ESD events. For more information please see Appendix 1. A Single Pole Double Throw or SPDT RF switch is used to toggle between the headset and embedded antenna. The switch being in front of the LNA and in the vicinity of strong cellular signals should introduce minimal loss to the system and offer high linearity. To know more about Infineon solutions for RF Switches, please refer to application note AN175. A Low Noise Amplifier or LNA follows the switch, which significantly reduces the noise figure of the whole receiver chain, thereby improving the receiver sensitivity. However, there are a few challenges in the design of the LNA for this purpose. Using it in a hand held device demands low current consumption and high linearity due to the coexistence of cellular bands. In a system with internal antenna, due to the very small size, the antenna impedance is very high and thus the LNA has to be matched to this high impedance and in addition offer a low noise figure. Application Note AN231, Rev. 1.0 6 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Overview 2 Overview This application note shows the performance of Infineon’s BGA728L7 as an LNA for FM radio. BGA728L7 is a broadband MMIC originally targeted at mobile TV applications but may also being used for FM radio applications. It offers high integration including biasing, on/off switch and a low gain mode. The application note is divided in two parts. The first part shows the MMIC in a configuration that is optimized for low noise figure, in the other part the LNA is optimized for a good matching to 50 Ohms. Comparison of the two circuits.Table 1 gives a quick overview of the performance difference of the two circuits. Test conditions are the same for both configurations Table 1 Comparison of the two circuits. Optimized for Parameter Noise Figure Input matching Noise figure / dB 1.3 1.65 Gain / dB 14.3 16.4 Input return loss / dB 7.3 12.2 Output return loss / dB 9.7 9.6 Input 1dB compression point / dBm -9 -6.5 Application Note AN231, Rev. 1.0 7 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Circuit optimized for Noise Figure 3 Circuit optimized for Noise Figure 3.1 Summary of Measurement Results Table 2 Performance with min. NF at Vcc=Von=2.8 V, Vgs=0V Parameter Symbol Value Unit Frequency Range Freq 78-108 MHz DC Voltage Vcc 2.8 V DC Current Icc 5.7 mA Gain G 14.3 dB Pin=-30dBm Noise Figure NF 1.3 dB SMA and PCB loss of 0.1 dB included RLin 7.3 dB Pin=-30dBm RLout 9.7 dB Pin=-30dBm IRev 28.8 dB Pin=-30dBm Input P1dB IP1dB -9.3 Output P1dB OP1dB 4 dBm Input IP3 IIP3 -7.2 dBm Output IP3 OIP3 7.1 dBm k >1 -- Input Return Loss Output Return Loss Reverse Isolation Stability Application Note AN231, Rev. 1.0 Note/Test Condition dBm Measured @ 100MHz In-band, f1=100MHz, f2=101MHz, Pin=-30dBm Unconditionally stable from DC to 10GHz 8 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Circuit optimized for Noise Figure 3.2 Schematic Diagram C4 1µF Von, 2.8V C1 270pF In 1 VCC, 2.8V 6 7 L2 150nH C6 9pF Out 2 BGA728L7 5 L1 470nH 3 TSLP-7-6 4 Top View VCC, 2.8V C5 10nF Figure 2 Table 3 Schematic diagram for minimum NF. Bill-of-Materials for minimum NF Symbol Value Unit Size Manufacturer C1 270 pF 0402 Various Input matching C4 1 uF 0402 Various HF to ground C5 10 nF 0402 Various HF to ground C6 9 pF 0402 Various Output matching L1 470 nH 0603 Tayio Yuden LK DC Feed/ Input matching L2 150 nH 0402 Murata LQG15A Output matching N1 BGA728L7 TSLP-7-1 Infineon Technologies Application Note AN231, Rev. 1.0 9 / 28 Comment SiGe:C LNA MMIC 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Circuit optimized for Noise Figure 3.3 Measured Graphs Insertion Power Gain InBand 20 15 10 5 78 MHz 14.89 dB 0 110 MHz 14.3 dB -5 -10 -15 -20 0 Figure 3 100 200 300 Frequency (MHz) 400 500 Insertion power gain at minimum NF. Noise figure 2 NF(dB) 1.8 78 MHz 1.249 dB 1.6 110 MHz 1.309 dB 1.4 1.2 1 78 Figure 4 86 94 Frequency (MHz) 102 110 Noise figure at minimum NF. Application Note AN231, Rev. 1.0 10 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Circuit optimized for Noise Figure Out of band attenuation 20 15 10 1575 MHz -19.45 dB 5 900 MHz -22.12 dB 0 2400 MHz -33.9 dB -5 5000 MHz -27.16 dB -10 -15 -20 -25 -30 -35 -40 0 Figure 5 1000 2000 3000 4000 5000 6000 Frequency (MHz) 7000 8000 700 800 9000 10000 Out-of-band Gain at minimum NF Input Matching 0 78 MHz -7.289 dB -5 110 MHz -7.395 dB -10 -15 -20 -25 0 Figure 6 100 200 300 400 500 600 Frequency (MHz) 900 1000 Input matching at minimum NF. Application Note AN231, Rev. 1.0 11 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Circuit optimized for Noise Figure Output Matching 0 -5 110 MHz -9.717 dB -10 -15 -20 78 MHz -14.99 dB -25 -30 0 Figure 7 100 200 300 Frequency (MHz) 400 500 400 500 Output matching of at minimum NF. Reverse Isolation 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 78 MHz 28.82 110 MHz 29.18 0 Figure 8 100 200 300 Frequency (MHz) Reverse isolation at minimum NF. Application Note AN231, Rev. 1.0 12 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Circuit optimized for Noise Figure Compression point at 1dB 20 -27 dBm 14.69 dB -9.693 dBm 13.69 dB Gain(dB) 15 10 5 0 -27 Figure 9 -22 -17 -12 Pin (dBm) -7 -2 0 Input P1dB compression point at minimum NF. Stability K Factor 10 9 8 7 6 5 4 34.975 MHz 1.894 3 2 1 0 0 Figure 10 2000 4000 6000 Frequency (MHz) 8000 10000 Stability factor K at minimum NF. Application Note AN231, Rev. 1.0 13 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Circuit optimized for Noise Figure Stability Mu factor Mu2 factor 5 Mu1 factor 4 3 2 1 0 0 2000 4000 6000 Frequency (MHz) Figure 11 Stability factor µ1 and µ2 at minimum NF. Figure 12 Output 3 order intermodulation distortion at minimum NF. 8000 10000 rd Application Note AN231, Rev. 1.0 14 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Circuit optimized for Noise Figure 0.8 1.0 Z Parameters Input output matching 2. 0 6 0. Z11 Swp Max 110MHz 0. 4 Z22 3. 0 0 4. 10.0 5.0 4.0 3.0 2.0 1.0 0.8 0.6 0.4 0.2 0 78 MHz r 1.0849 x -0.367454 78 MHz r 2.50056 10.0 x 0.209126 110 MHz r 2.24402 x -0.672187 -10.0 0.2 2 -5. 0 -0. 5.0 110 MHz r 1.87693 x 0.357998 -4 .0 .0 Figure 13 - 0 2. -1.0 -0.8 -0 .6 .4 -3 -0 Swp Min 78MHz Input and Output impedance at minimum NF. Application Note AN231, Rev. 1.0 15 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Circuit optimized for input matching 4 Circuit optimized for input matching 4.1 Summary of Measurement Results Table 4 Performance with best input matching at Vcc=Von=2.8 V, Vgs=0V Parameter Symbol Value Unit Frequency Range Freq 78…110 MHz DC Voltage Vcc 2.8 V DC Current Icc 5.8 mA Gain G 14.6 dB Pin=-30dBm Noise Figure NF 1.65 dB SMA and PCB loss of 0.10 dB included RLin 12.2 dB Pin=-30dBm RLout 9.6 dB Pin=-30dBm IRev 28.8 dB Pin=-30dBm Input P1dB IP1dB -10.4 Output P1dB OP1dB 3.7 dBm Input IP3 IIP3 -6.4 dBm Output IP3 OIP3 8.2 dBm k >1 -- Input Return Loss Output Return Loss Reverse Isolation Stability Application Note AN231, Rev. 1.0 Note/Test Condition dBm Measured @ 100MHz In-band, f1=100MHz, f2=101MHz, Pin=-30dBm Unconditionally stable from DC to 10GHz 16 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Circuit optimized for input matching 4.2 Schematic Diagram Von, 2.8V C1 39pF In 1 C4 1µF VCC, 2.8V 6 7 L2 150nH C6 9pF Out 2 BGA728L7 5 L1 180nH 3 TSLP-7-6 4 Top View VCC, 2.8V C5 10nF Figure 14 Table 5 Schematic diagram for best input matching. Bill-of-Materials for best input matching Symbol Value Unit C1 39 pF 0402 Various Input matching/DC block C4 1 uF 0402 Various HF to ground C5 10 nF 0402 Various HF to ground C6 9 pF 0402 Various Output matching L1 180 nH 0402 Murata LQG15A DC Feed/ Input matching L2 150 nH 0402 Murata LQG15A Output matching N1 BGA728L7 TSLP-76 Infineon Technologies Application Note AN231, Rev. 1.0 Size Manufacturer 17 / 28 Comment SiGe:C MMIC LNA 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Circuit optimized for input matching 4.3 Measured Graphs Insertion Power Gain InBand 20 15 10 78 MHz 15.26 dB 5 110 MHz 14.6 dB 0 -5 -10 -15 -20 0 Figure 15 100 200 300 Frequency (MHz) 400 500 Insertion Power Gain with best input matching Noise figure 2 NF(dB) 1.8 78 MHz 1.654 dB 110 MHz 1.471 dB 1.6 1.4 1.2 1 78 Figure 16 86 94 Frequency (MHz) 102 110 Noise figure with best input matching Application Note AN231, Rev. 1.0 18 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Circuit optimized for input matching Out of band attenuation 20 15 10 900 MHz -23.41 dB 5 2400 MHz -32.97 dB 0 -5 1575 MHz -19.12 dB -10 5000 MHz -24.85 dB -15 -20 -25 -30 -35 -40 0 Figure 17 1000 2000 3000 4000 5000 6000 Frequency (MHz) 7000 8000 700 800 9000 10000 Out-of-Band attenuation with best input matching Input Matching 0 -5 110 MHz -12.21 dB -10 -15 -20 78 MHz -30.82 dB -25 -30 -35 0 Figure 18 100 200 300 400 500 600 Frequency (MHz) 900 1000 Input matching with best input matching Application Note AN231, Rev. 1.0 19 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Circuit optimized for input matching Output Matching 0 -5 110 MHz -9.599 dB -10 -15 78 MHz -15.49 dB -20 -25 -30 0 Figure 19 100 200 300 Frequency (MHz) 400 500 400 500 Output Matching with best input matching Reverse Isolation 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 78 MHz 28.79 110 MHz 29.18 0 Figure 20 100 200 300 Frequency (MHz) Reverse Isolation with best input matching Application Note AN231, Rev. 1.0 20 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Circuit optimized for input matching Compression point at 1dB 20 -27 dBm 15.09 dB -10.36 dBm 14.09 dB Gain(dB) 15 10 5 0 -27 Figure 21 -22 -17 -12 Pin (dBm) -7 -2 0 Input 1dB ompression point with best input matching Stability K Factor 10 9 8 7 6 5 4 92.73 MHz 2.353 3 2 1 0 0 Figure 22 2000 4000 6000 Frequency (MHz) 8000 10000 Stability factor K with best input matching. Application Note AN231, Rev. 1.0 21 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Circuit optimized for input matching Stability Mu factor Mu2 factor 5 Mu1 factor 4 3 2 1 0 0 2000 4000 6000 Frequency (MHz) 8000 Figure 23 Stability factor µ1 and µ2 of with best input matching Figure 24 Output 3 order intermodulation distortion with best input matching 10000 rd Application Note AN231, Rev. 1.0 22 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Circuit optimized for input matching 0.8 1.0 Z Parameters Input output matching Swp Max 110MHz 2. 0 6 0. Z11 0. 0 0 4. 5.0 10.0 5.0 4.0 3.0 2.0 10.0 1.0 0.8 0.4 0.2 3. 110 MHz r 1.64196 x 0.088891 -10.0 0.6 78 MHz r 0.941334 x -0.010687 0.2 78 MHz r 0.924681 x -0.320277 2 -0. 0 0 110 MHz r 1.77503 x 0.523561 -5. 4 Z22 -4 .0 .0 Figure 25 - 0 2. -1.0 -0.8 -0 .6 .4 -3 -0 Swp Min 78MHz Input and Output impedance with best input matching. Application Note AN231, Rev. 1.0 23 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Evaluation Board 5 Evaluation Board Figure 26 Picture of Evaluation Board Figure 27 PCB Layer Information Application Note AN231, Rev. 1.0 24 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Evaluation Board Appendix 1: ESD protection circuit for system level ESD robustness Introduction With the advancement in miniaturization of semiconductor structures, ESD handling capability of the devices is becoming a concern. Increasing ESD handling capability of the I/O ports costs additional chip size and affects the I/O capacitance significantly. This is very important for high frequency devices, especially when high linearity is required. Therefore, tailored and cost effective ESD protection devices can be used to build up an ESD protection circuit. To handle ESD events during assembly, devices normally have on-chip ESD protection according to the device level standards e.g. “Human Body Model” JEDEC 22-A-115. To fulfill the much more stringent system level ESD requirements according to IEC61000-4-2 as shown in Figure 28, the external ESD protection circuit has to handle the majority of the ESD strike. The best external ESD protection is achieved using a TVS diode assisted by additional passive components. m6 ESD_current, A 60 Reference Pulse 15kV contact discharge according IEC61000-4-2 m6 time=1.507nsec ESD_current=57.68 A m7 time=30.01nsec ESD_current=29.43 A 40 m7 m8 20 m8 time=60.01nsec ESD_current=15.18 A 0 0 20 40 60 80 100 120 140 160 180 200 time, nsec Figure 28 ESD test pulse according to system level specification IEC61000-4-2 – Contact Discharge 15kV Some examples of RF applications addressed by the Infineon ESD protection proposal are given below: • FM Radio (76 MHz -110 MHz) • WLAN 802.11b/g/n (2.4 GHz, Tx ~ +20 dBm) • Bluetooth (2.4 GHz, Tx ~ +20 dBm) • Automatic Meter Reading, AMR (900 MHz, TX ~ +20 dBm) • Remote Keyless Entry, RKE (315 MHz - 434 MHz - 868 MHz - 915 MHz, Tx~13 dBm) • GPS (1575 MHz, Rx only but can be affected by RF interferer) For an ESD protection device tailored for medium power RF signals (=< +20 dBm), following requirements are essential: 1. RF requirements a) Bidirectional characteristic to handle DC free signals without clipping / signal distortion b) A highly symmetrical behavior of the ESD device for positive and negative voltage swings is mandatory to keep the power level of even Harmonics low c) Breakdown voltage of 5 V-10V, to avoid signal distortion at high RF voltage swing applied at the TVS diode, located close to the antenna d) High linearity e) Low leakage current and stable diode capacitance vs. RF voltage swing f) Ultra low diode capacitance is mandatory Application Note AN231, Rev. 1.0 25 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Evaluation Board 2. ESD requirements a) Lowest dynamic resistance Rdyn to offer best protection for the RFIC; Rdyn is characterized by Transmission Line Pulse (TLP) measurement b) Very fast switch-on time (<<1nsec) to ground the initial peak of an ESD strike according to IEC61000-4-2 c) No performance degradation over a large number of ESD zaps (>1000) Two-step ESD Protection approach General structure for a 2-step ESD approach according to Figure 29 enables to split the entire ESD current between the internal and external ESD protection device. The external device is much more robust and handles the majority of the ESD current. To avoid any impact on the RF behavior of the system and to minimize non linearity effects, the TVS diode should possess an ultra low device capacitance. Therefore the bi-directional (symmetrical) Infineon TVS Diode ESD0P2RF is well suited, which provides a diode capacitance as low as 0.2 pF and a Rdyn of only 1 Ohm. ESD robustness can be improved one step more by adding a small serial resistor between the external TVS diode and the RF amplifier input. A resistor of ~2.2 Ohm is a good compromise between additional ESD performance and insertion loss. The TVS diode ESD0P2RF in combination with the 2.2 Ohm ESD resistor would incur less than 0.23dB insertion loss up to 3 GHz. Figure 29 Smart 2-step ESD protection approach based on external and internal ESD protection structure For further ESD improvement it is highly recommend to add a serial capacitor (C1). The capacitor cuts off most of the high energy created by the ESD strike. For better ESD robustness, C1 should be as small as possible, but has to match to the intended application frequency as well. For a broadband ESD protection (80MHz…3GHz) C1 should be about 100pF…150pF. Optional matching can be implemented with a serial inductor L1 for a dedicated frequency. In combination with L1, C1 can be reduced significantly which improves the ESD performance. + Vcc OUT LNA/ Switch/ Filter Internal ESD Protection RX antenna RF IC input C1 optional L1 ESD_ resistor ESD_protection_2.vsd Figure 30 Standard ESD protection topology with optional ESD resistor, blocking capacitor and a serial inductor Application Note AN231, Rev. 1.0 26 / 28 2010-08-02 BGA728L7 BGA728L7 as a LNA for FM Radio Authors Authors Anthony Thomas, Application Engineer of “RF and Protection Devices” Dr. Lin Chih-I, Senior Staff Engineer of “RF and Protection Devices” Dietmar Stolz, Staff Engineer of Business Unit “RF and Protection Devices” Application Note AN231, Rev. 1.0 27 / 28 2010-08-02 w w w . i n f i n e o n . c o m Published by Infineon Technologies AG AN231