National Semiconductor Application Note 2014 Gerrit de Wagt and Jaimy de Koning May 4, 2010 General Description tercept only, reducing calibration effort significantly. The device operates with a single supply from 2.7V to 5V. The LMH2110 has an RF power detection range from -40 dBm to 5 dBm and is ideally suited for use in combination with a directional coupler. Alternatively a resistive divider can be used as well. The device is active for EN = High, otherwise it is in a low power consumption shutdown mode. To save power and prevent discharge of an external filter capacitance, the output (OUT) is high-impedance during shutdown. The LMH2110 power detector is offered in a tiny 6-bump microSMD package. Figure 1 shows the LMH2110 Evaluation Board. The evaluation board is designed to help the evaluation of the LMH2110, which is a 45 dB Logarithmic RMS power detector particularly suited for accurate power measurement of modulated RF signals that exhibit large peak-to-average ratios, i.e. large variations of the signal envelope. Such signals are encountered in W-CDMA and LTE cell phones. The RMS measurement topology inherently ensures a modulation insensitive measurement. The device has an RF frequency range from 50 MHz to 8 GHz. It provides an accurate, temperature and supply insensitive, output voltage that relates linearly to the RF input power in dBm. The LMH2110's excellent conformance to a logarithmic response enables an easy integration by using slope and in- LMH2110 Evaluation Board LMH2110 Evaluation Board 30109716 FIGURE 1. LMH2110 Evaluation Board Basic Operation The circuit operates with a single supply form 2.7V to 5V and has an RF power detection range from −40 dBm to 5 dBm. The board consist of a single LMH2110 along with external components soldered on a printed circuit board. External sup- ply voltages and input signals can be applied to the on-board connectors. The supply voltage is applied with connectors P21 (VDD) and P22 (GND). The RF input signal is applied by SMA connector P1. This RF signal is applied through an RF generator and is connected with a 50Ω SMA cable. The detector output can be measured via BNC connector P3. AN-2014 © 2010 National Semiconductor Corporation 301097 www.national.com AN-2014 To guarantee a correct operation a voltage divider formed by R2 and R3 is present on the evaluation board. The absolute maximum ratings are also exceeded when the enable (EN) is switched to HIGH (from shutdown to active mode) while the supply voltage is switched off. This situation should be prevented at all times. A solution to protect the device is the resistor R1 of 1 kΩ in series with the enable input to limit the current. An overview of the various jumper positions on the board is given in Figure 2. The settings of these jumpers and their functions are listed in Table 1. Configuration The LMH2110 evaluation board can be configured via jumper settings. The device is active when EN = High. This can be accomplished by setting the jumper J4 to VDD or by using external control on P4 by setting the jumper J4 to EN. Since the device has an internal operating voltage of 2.5V, the voltage level on the enable should not be higher than 3V to prevent damage to the device. Also enable voltage levels lower than 400 mV below GND should be prevented. In both cases the ESD devices start to conduct when the enable voltage range is exceeded and excessive current will be drawn. 30109710 FIGURE 2. Jumper Positions TABLE 1. Jumper and Header Overview Bold face jumper settings refer to the factory default configuration. Jumper J4 www.national.com Function Enable Jumper Position Description 1–2 Active, Connects Enable Pin to VDD 3–4 External Control, Connects Enable Pin to Enable P4 5-6 Shutdown, Connects Enable Pin to GND 2 AN-2014 Measurement Setup The performance of the LMH2110 can be measured with the setup shown in Figure 3. 30109712 FIGURE 3. Measurement Setup An external power supply provides a voltage of 2.7V to 5V to the evaluation board. An accurate and stable RF Signal Generator is used to produce the test signal. It is recommended to use low loss cables to ensure reliable measurement data. The detected output voltage can be measured with a Digital Voltage Meter (DVM). Figure 4 depicts the output voltage versus frequency for various power levels on RFIN. The frequency range is from 10 MHz to 10 GHz. Figure 5 depicts the output voltage versus RF input power for various frequencies. 30109709 FIGURE 5. Output Voltage vs. RF Input Power 30109708 FIGURE 4. Output Voltage vs. Freqency 3 www.national.com AN-2014 Schematic 30109705 FIGURE 6. Evaluation Board Schematic Bill of Material TP1 Test Point GND The Bill of Material (BOM) of the evaluation board is given in Table 2. U1 µSMD LMH2110TM Board Layout TABLE 2. Bill of Material Designator Description Comment C1, C2 0603 Capacitor 10 nF C3, C4, C6 0603 Capacitor 10 pF C5 0603 Capacitor 1 pF C7 0603 Capacitor 10 µF J4 Header 2x3 P1 Connector SMA P21, P22 Connector Banana P3 Connector BNC P4 Connector BNC R1 0603 Resisitor 1 kΩ R2, R3 0603 Resistor 100 kΩ R4 0603 Resisitor 0Ω www.national.com As with any other RF device, careful attention must me paid to the board layout. If the board layout isn’t properly designed, performance might be less than can be expected for the application. The LMH2110 is designed to be used in RF applications, having a characteristic impedance of 50Ω. To achieve this impedance, the input of the LMH2110 needs to be connected via a 50Ω transmission line. Transmission lines can be created on PCBs using microstrip or (grounded) coplanar waveguide (GCPW) configurations. In order to minimize injection of RF interference into the LMH2110 through the supply lines, the PCB traces for VDD and GND should be minimized for RF signals. This can be done by placing a small decoupling capacitor between the VDD and GND. It should be placed as close as possible to the VDD and GND pins of the LMH2110. Figure 7 shows the component locations of the LMH2110 evaluation board and Figure 8 shows the board layout of the LMH2110 evaluation board. 4 AN-2014 LMH2110 Evaluation Board 30109711 FIGURE 7. Component Locations of Evaluation Board 30109715 FIGURE 8. Board Layout of Evaluation Board 5 www.national.com LMH2110 Evaluation Board Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Design Support Amplifiers www.national.com/amplifiers WEBENCH® Tools www.national.com/webench Audio www.national.com/audio App Notes www.national.com/appnotes Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns Data Converters www.national.com/adc Samples www.national.com/samples Interface www.national.com/interface Eval Boards www.national.com/evalboards LVDS www.national.com/lvds Packaging www.national.com/packaging Power Management www.national.com/power Green Compliance www.national.com/quality/green Switching Regulators www.national.com/switchers Distributors www.national.com/contacts LDOs www.national.com/ldo Quality and Reliability www.national.com/quality LED Lighting www.national.com/led Feedback/Support www.national.com/feedback Voltage References www.national.com/vref Design Made Easy www.national.com/easy www.national.com/powerwise Applications & Markets www.national.com/solutions Mil/Aero www.national.com/milaero PowerWise® Solutions Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors SolarMagic™ www.national.com/solarmagic PLL/VCO www.national.com/wireless www.national.com/training PowerWise® Design University THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. NATIONAL MAKES NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY OR COMPLETENESS OF THE CONTENTS OF THIS PUBLICATION AND RESERVES THE RIGHT TO MAKE CHANGES TO SPECIFICATIONS AND PRODUCT DESCRIPTIONS AT ANY TIME WITHOUT NOTICE. NO LICENSE, WHETHER EXPRESS, IMPLIED, ARISING BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL PROPERTY RIGHTS IS GRANTED BY THIS DOCUMENT. TESTING AND OTHER QUALITY CONTROLS ARE USED TO THE EXTENT NATIONAL DEEMS NECESSARY TO SUPPORT NATIONAL’S PRODUCT WARRANTY. EXCEPT WHERE MANDATED BY GOVERNMENT REQUIREMENTS, TESTING OF ALL PARAMETERS OF EACH PRODUCT IS NOT NECESSARILY PERFORMED. NATIONAL ASSUMES NO LIABILITY FOR APPLICATIONS ASSISTANCE OR BUYER PRODUCT DESIGN. BUYERS ARE RESPONSIBLE FOR THEIR PRODUCTS AND APPLICATIONS USING NATIONAL COMPONENTS. PRIOR TO USING OR DISTRIBUTING ANY PRODUCTS THAT INCLUDE NATIONAL COMPONENTS, BUYERS SHOULD PROVIDE ADEQUATE DESIGN, TESTING AND OPERATING SAFEGUARDS. EXCEPT AS PROVIDED IN NATIONAL’S TERMS AND CONDITIONS OF SALE FOR SUCH PRODUCTS, NATIONAL ASSUMES NO LIABILITY WHATSOEVER, AND NATIONAL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY RELATING TO THE SALE AND/OR USE OF NATIONAL PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR PURPOSE, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY RIGHT. LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS PRIOR WRITTEN APPROVAL OF THE CHIEF EXECUTIVE OFFICER AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: Life support devices or systems are devices which (a) are intended for surgical implant into the body, or (b) support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in a significant injury to the user. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness. National Semiconductor and the National Semiconductor logo are registered trademarks of National Semiconductor Corporation. All other brand or product names may be trademarks or registered trademarks of their respective holders. AN-2014 Copyright© 2010 National Semiconductor Corporation For the most current product information visit us at www.national.com National Semiconductor Americas Technical Support Center Email: [email protected] Tel: 1-800-272-9959 www.national.com National Semiconductor Europe Technical Support Center Email: [email protected] National Semiconductor Asia Pacific Technical Support Center Email: [email protected] National Semiconductor Japan Technical Support Center Email: [email protected]