Embedded Systems Design Europe - August/September 2008 - (Page 29)

psu design rents reaching maximum peaks of 3A and a maximum average of approximately 1A. To reduce the current peaks and the associated radio problems, you should make use of the techniques described in two papers by Jose Ignacio Garate and others. A capacitor of high value and low ESR is highly recommended. Measurement results (Tables 2 and 3) don’t include losses in the common-mode input ﬁlter or the protection circuitry. Table 2 gives values for the power supply’s input and output variables for different input voltages under no-load conditions. The minimum current draw achieved is 5 mA. You can reduce that to 3 mA, but the low-value resistor necessary to achieve 3 mA causes the control loop to become unstable. To prevent self oscillation and to accommodate component tolerances, a security margin is introduced by setting the current draw slightly higher than 5 mA. As shown in Table 3, the optimum efﬁciency is reached at normal conditions with a nominal load. Figure 5 shows the efﬁciency for different output currents. For commercially available, isolated power supplies with similar characteristics, we found that the lowest noload current draw is around 20 mA. By designing a circuit with off-the-shelf components that obtains a quiescent current of 5 mA, we have surpassed our goal of 12 mA. 4, 5 2. 3. 4. 5. Standard Clariﬁes Future of WLAN,” Texas Instruments Inc., 2002. PDF available on http://focus.ti.com/docs/ solution/folders/print/47.html. Haroun, Ibrahim, Ioannis Lambadaris, and Roshdy Hafez. “RF System Issues in Wireless Sensor Networks,” Microwave Engineering Europe, Nov. 2005, pp. 31–35. PDF available on www.mwee.com/ mag_archive/mwee1105.html. Application Note 664, “Feedback Isolation Augments Power-Supply Safety and Performance,” Maxim Integrated Products, Jan 22, 2001 (see www.maximic.com/an664). Also see June 19, 1997 issue of EDN (www.edn.com/archives/ 1997/061997/13df_04.htm). Garate, Jose Ignacio, Jose Miguel de Diego, and Maite Sierra. “Consequences of Discontinuous Current Consumption on Battery Powered Wireless Terminals,” [ISIE06, Paris, France, Oct. 2006]. IEEE Explore: http://ieeexplore.ieee.org/xpl/ freeabs_all.jsp?arnumber=4153462 Garate, Jose Ignacio and Jose Miguel de Diego. “Improvements of Power Supply Systems in Machine to Machine Modules and Fixed Cellular Terminals with Discontinuous Current Consumption,” (Digests 9th ICIT06, Mumbai, India, Dec. 2006.) cy, Low IQ, Step-Up DC-DC Controller,” 2002, Maxim Integrated Products, Datasheet 190263; Rev 2; 3/02. www.maxim-ic.com/quick _view2.cfm/qv_pk/1030 Jose Miguel de Diego (jm.dediego@ehu. es) has a BS in electrical engineering from the E.T.S.I.I. of Navarra University, San Sebastián, and a doctorate in industrial engineering from the High School of Engineering of Bilbao, Spain. His research areas are power-supply systems and renewable energies, and he has worked in R&D at industrial electronics companies, including Ericsson Radio S.A., Spain. Jose Ignacio Garate (joseignacio. garate@ehu.es) has a BS and an MS degrees from the High School of Engineering of Bilbao, Spain, both in telecommunication engineering. He is working on his doctorate on discontinuous current consumption in battery-powered wireless terminals and output power control for radio-frequency power ampliﬁers. He worked in the R&D departments of Ericsson Radio S.A., Spain, and Ericsson ABB, Lund and Gable, Sweden. Javier Monsalve Kägi (javier.monsalve@ maxim-ic.com) graduated with a BSEE and MSEE from Worcester Polytechnic Institute, Massachusetts. He is a ﬁeld applications engineer at Maxim Integrated Products, Inc., and previously worked for Spanish companies doing analog and digital electronic design in avionics and designing an IC for temperature measurement and voice synthesis (thermometer for the visual impaired). FURTHER READING: “MAX1649/MAX1651, 5V/3.3V or Adjustable, High-Efﬁciency, Low-Dropout, Stepdown DC-DC Controllers,” Maxim Integrated Products, Datasheet 10-0305, Rev 2; 9/95. www. maxim -ic.com/quick_view2.cfm/qv_pk/1028 “MAX1771, 12V or Adjustable, High-Efﬁcien- ENDNOTES: 1. Carney, William. “IEEE 902.11g: New Draft 024-025-026-027-028-029_ESDE.indd 29 28/08/08 13:52:18 http://focus.ti.com/docs/solution/folders/print/47.html http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1030 http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1030 http://www.mwee.com/mag_archive/mwee1105.html http://www.mwee.com/mag_archive/mwee1105.html http://www.maxim-ic.com/an664 http://www.maxim-ic.com/an664 http://www.edn.com/archives/1997/061997/13df_04.htm http://www.edn.com/archives/1997/061997/13df_04.htm http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=4153462 http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=4153462 http://www.mazim-ic.com/quick_view2.cfm/qv_pk/1028 http://www.mazim-ic.com/quick_view2.cfm/qv_pk/1028 http://www.mazim-ic.com/quick_view2.cfm/qv_pk/1028 http://www.syslogic.com http://www.syslogic.com

Table of Contents Feed for the Digital Edition of Embedded Systems Design Europe - August/September 2008

Embedded Systems Design Europe - August/September 2008 Contents TI Overhauls DSP Lineup, Adds 15 Processors QNX Publishes Source Code for File System Congatec to Take on Proprietary Market Swiss Multicore Project Wins Microsoft Grant OpenCores Bundles Development Tool ARM Compiler Boosts Freescale i.MX31 LabVIEW Updated for Multicore and Wireless Cover Feature: Interactive Tool Supports Multiprocessor SoC Design Wanted: Benchmaking for Embedded VMM Hypervisors Graphical Design Empowers Spider Robots Building a Power Supply for Discontinuous Transmission Wireless Networks RTOS Selection & Best Practices Achieving Cache Coherence in a MIPS32 Multicore Design New Products Advertising Contacts

Embedded Systems Design Europe - August/September 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.