Application Note. Power Management Considerations with u-blox 5 designs. Application note. your position is our focus

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1 u-blox AG Zürcherstrasse Thalwil Switzerland Phone Fax Power Management Considerations with designs Application note Abstract This document describes the power management considerations for module or chipset designs. Low power modes are described with diagrams showing acquisition time vs. estimated power consumption. Where appropriate, differences in performance due to the selection of modes are illustrated. your position is our focus Application Note

2 Title Doc Type Doc Id Revision Index Power Management Considerations with designs Application note GPS.G5-CS B Date Name Status / Comments Initial version 15/05/2008 SV A 23/07/2008 SV Low Power Mode B 06/10/2008 TG CI, Power Values We reserve all rights to this document and the information contained therein. Reproduction, use or disclosure to third parties without express permission is strictly prohibited. For most recent documents, please visit Performance characteristics shown in this document are estimates only and do not constitute a warranty or guarantee of product performance. u-blox does not support any applications in connection with weapon systems. Since u-blox products are not designed for use in life-support and commercial aviation applications they shall not be used in such products. In devices or systems whereby malfunction of these products can be expected to result in personal injury and casualties, u-blox customers using or selling these products do so at their own risk and agree to keep u-blox harmless from any consequences. u-blox reserves the right to make changes to this product, including its circuits and software, in order to improve its design and/or performance, without prior notice. u-blox makes no warranties, neither expressed nor implied, regarding the information and specifications contained in this document. u-blox assumes no responsibility for any claims or damages arising from information contained in this document, or from the use of products and services detailed therein. This includes, but is not limited to, claims or damages based on the infringement of patents, copyrights, mask work and/or other intellectual property rights. Power Management Considerations with designs GPS.G5-CS B Application note

3 1 Power Management Options This application note describes ways of configuring GPS receivers to reduce power consumption while maintaining a high level of performance. These are important design goals for portable systems. offers various options for applications with different power requirements by means of its flexible configuration of supply voltage and power modes. 1.1 Hardware Options modules modules support three kinds of power supply models: 3V Module RF IN V Vcc Figure 1: modules with supply voltage of 3V nominal ( V) 1.8V Module RF IN V Vcc Figure 2: modules with supply voltage of 1.8V nominal ( V). Planned for Q RF IN 1.8V Module Ext. Supply DC/DC Converter V Vcc Figure 3: modules supplied by DC/DC converter. For more information, consult our manuals (see Related Documents) Power Management Considerations with designs Application note Power Management Options GPS.G5-CS B Page 3

4 1.1.2 ICs Depending on the application, ICs support different kinds of power supply models. Some examples are: V ICs RF Baseband RF IN TCXO ( V) or Crystal Figure 4: Single supply voltage from 2.5V to 3.6 V Ext. Supply DC/DC Converter V ICs RF Baseband RF IN TCXO ( V) or Crystal Figure 5: Single supply voltage of 1.8V nominal ( V) Ext. Supply DC/DC Converter DC/DC Converter V 1.4 V ICs RF Baseband RF IN TCXO (1.75-2V) or Crystal Figure 6: Separate supply of 1.8V nominal ( V) and 1.4V ( V) For more information, consult our manuals (see Related Documents) Power Management Considerations with designs Application note Power Management Options GPS.G5-CS B Page 4

5 1.2 Configurable Software Options Power modes technology offers power-optimized architecture with built-in autonomous power saving functions that minimize power consumption at any given time. can be operated in two different power modes: Maximum Performance and Eco Mode. In both cases, the receiver is operated in continuous mode. The difference lies in how the acquisition engine is used. The Maximum Performance mode freely uses the acquisition engine, resulting in the best possible TTFF, while Eco Mode optimizes the use of the acquisition engine to deliver lower current consumption. At medium to strong signals, there is almost no difference for acquisition and tracking performance in these modes Maximum Performance mode In Maximum Performance mode, receivers use the acquisition engine at full performance to search for all possible satellites until the Almanac is completely downloaded. As a consequence, tracking current consumption level will be achieved when: A valid GPS position is fixed Almanac is entirely downloaded Ephemeris for all satellites in view are valid Eco mode In Eco mode, receivers use the acquisition engine to search for new satellites only when needed for navigation: In cold starts, searches for enough satellites to navigate and optimizes use of the acquisition engine to download their ephemeris. In non-cold starts, focuses on searching for visible satellites whose orbits are known from the Almanac. In Eco mode, the acquisition engine limits use of its searching resources to minimize power consumption. As a consequence the time to find some satellites at weakest signal level might be slightly increased in comparison to the Max. performance mode. deactivates the acquisition engine as soon as a position is fixed and a sufficient number (at least 4) of satellites are being tracked. The tracking engine continues to search and track new satellites without orbit information. Power Management Considerations with designs Application note Power Management Options GPS.G5-CS B Page 5

6 1.2.2 Low Power Modes A new low power mode will be available with future firmware versions. The low power mode will allow shutting down the receiver and waking it up automatically at predefined intervals. The chapter below describes how one can control the power management of the receiver while the low power modes are not yet available Hardware approach receivers can be put into an idle state by use of an external power control. Connection of battery power to the battery backup pin will minimize the startup time (hot start). Software Power Control from the application RF IN Module V Vcc + V_BAT Figure 7: External power control When using an external power switch and battery backup to optimize consumption and navigation performance, it is recommended to control u-blox5 power from the application as shown in the following state diagram (Figure 8) Power Management Considerations with designs Application note Power Management Options GPS.G5-CS B Page 6

7 Power ON after x sec (typ. 120s) and try acquisition again Power OFF Power ON Power ON Power OFF, if no fix after x sec (min. 60s, typ. 120s) SLEEP If acquisition time < x sec (typ. 120s) and got 1st position valid (monitor "valid" status in NMEA-RMC or UBX-NAV-STATUS message) Get 1 st Fix With UBX protocol: Wait "Position within limits in UBX-NAV-STATUS Verify that Real Time Clock (RTC) is calibrated to minimize startup time (hot start). The UBX-MON-HW message allows monitoring RTC calibration. With NMEA protocol: Wait x sec (typ. 2s) for RTC calibration. Get Continuous Fix Getting sufficient fixes allows the acquisition of more satellites, which can improve position accuracy. Enough Fixes Figure 8: Simplified diagram to control power externally This approach allows any application to efficiently shut down the u-blox5 receiver periodically to reduce its power consumption and integrate the automatic power saving control on the application side Software approach If no external power switch can be implemented it may be possible to switch off the entire receiver by sending commands and to wake it up either by sending a command or by an interrupt on the EXTINT input. One of these commands is the Control GPS (UBX-CFG-RST) command, which can reduce current consumption to less than 10mA by switching off the u-blox5 RF part. For more information on software low power options please contact your u-blox support team. Power Management Considerations with designs Application note Power Management Options GPS.G5-CS B Page 7

8 2 Performance 2.1 Supply voltage datasheet and hardware integration manuals provide power supply specifications with module and IC designs. (see Related Documents). Good performance requires a clean and stable power supply with minimal ripple. Care needs to be exercised in selecting a strategy to achieve this. Placing a resistance at Vcc can negatively impact performance. For better performance, use an LDO to provide a clean supply at Vcc and consider the following: Wide power lines or even power planes are preferred. Place LDO near the module. Avoid resistive components in the power line (e.g. narrow power lines, coils, resistors, etc.). Placing a filter or other source of resistance at Vcc can create significantly longer acquisition times. Power Management Considerations with designs Application note Performance GPS.G5-CS B Page 8

9 2.2 Power modes Current consumption Current consumption drops much faster in Eco mode than in the Max. Performance mode. Current [ma] Max. Performance 40 Eco mode Time [Seconds] Figure 9: Average acquisition current consumption for FW 5.00 (Hot/Warm/Aided starts) 1 Max. Performance mode 2 Eco mode 2 with FW 5.00 Acquisition max (ma) Acquisition typical (ma) Tracking (ma) Table 1: Typical current consumption for standard modules in different power modes 1 With good sky visibility. 2 Using KickStart modules increase current consumption by about 1mA. Consults our datasheet for latest figures. Compare the module peak current consumption (150 ma) with the power supply specification. 3 Average current consumption over the first 5 seconds. Power Management Considerations with designs Application note Performance GPS.G5-CS B Page 9

10 Current [ma] Max. Performance 40 Eco mode Time [min] Figure 10: Average acquisition current consumption for FW 5.00 (Cold starts) 3 Max. Performance mode 4 Eco mode 5 with FW 5.00 Acquisition max (ma) Acquisition typical (ma) 70 / Tracking (ma) 55 (after 1 min. typical) 46 (after 12.5 min. typical) 41 (after 1 min.) Table 2: Typical current consumption for standard modules in different power modes (Cold start) 4 Using KickStart modules increase current consumption by about 1mA. Consults our datasheet for latest figures. Compare the module peak current consumption (150 ma) with the power supply specification. 5 Average current consumption over the first 5 seconds and first 30 seconds. 6 Average current consumption measured over 30 minutes. Power Management Considerations with designs Application note Performance GPS.G5-CS B Page 10

11 2.2.2 Acquisition time At strong signals, there is no difference in acquisition time between the two power modes. Differences are noticeable at signal strengths below 138 dbm. At weakest signals the Maximum Performance mode provides more predictable acquisition time performance. Acquisition Time [s] Kickstart + Max. Performance Kickstart + Eco Standard + Max Performance 20 Standard + Eco Signal strength [dbm] Figure 11: Average acquisition time versus GPS signal strength in hot start scenarios Tracking At weak signals, no noticeable differences in tracking should be expected between Max. Performance and Eco modes. Max. Performance might provide an advantage in reacquisition after long periods of signal outage. 2.3 DDC bus With firmware version 4.00, DDC port communication brings an expected increase in current consumption of up to 20mA. With firmware version 5.00, the extra current consumption required from DDC port is lower. Power Management Considerations with designs Application note Performance GPS.G5-CS B Page 11

12 3 Changing Configuration 3.1 Power modes offers the option of two power modes to choose from: Maximum Performance mode enables the full capability of positioning, while Eco mode can be selected for reduced current consumption. The default configuration can be changed on all modules Default Settings modules with Kickstart run in Maximum Performance mode by default. modules without the KickStart feature operate in Eco mode by default. Power Mode Default settings on Eco Mode Standard modules (LEA-5A, LEA-5M and NEO-5M) Maximum Performance Mode KickStart modules (LEA-5S, LEA-5H, LEA-5T, LEA-5Q, NEO-5Q and TIM-5H) Table 3: Default Power mode on modules Software settings modules with firmware V4.01 or later (e.g. LEA-5H, LEA-5T and TIM-5H) : products with firmware V4.01 or later feature a configuration message (UBX-CFG-RXM) that allows switching between the two modes (refer to the Protocol Specification [4]). Settings can be stored to Flash or Backup Battery RAM memory using a save command (UBX-CFG-CFG). modules with firmware V4.00 : Receivers with firmware V4.00 can be reconfigured by sending the appropriate UBX binary command below: To configure LEA-5S, LEA-5Q, LEA-5H modules to Eco Mode : B D0 07 E8 03 F4 01 B0 04 E F To configure LEA-5A and LEA-5M modules to Max. Performance : B F E A B0 04 E F9 10 It is strongly recommended to save the modified settings to BBR and/or Flash (using the UBX-CFG-CFG command): B D FF FF AF For more information on Power supply specifications and power modes, check the latest LEA-5 Data Sheet [1], TIM-5 Data Sheet [2] or NEO-5 Datasheet [3]. ICs with firmware V4.01 or later: products with firmware V4.01 or later feature a configuration message (UBX-CFG-RXM) that allows switching between the two modes (refer to the Protocol Specification [4]). Settings can be stored to Flash or Backup Battery RAM memory using a save command (UBX-CFG-CFG). ICs with firmware V4.00 : For information regarding the software configuration of ICs with firmware version 4.00, contact u-blox support. Power Management Considerations with designs Application note Changing Configuration GPS.G5-CS B Page 12

13 3.1.3 Hardware settings ICs, LEA-5Q and NEO-5Q modules include a CFG_GPS0 pin, which enables the boot-time configuration of the power mode. These settings are described in Table 3. CFG_GPS0 Power Mode 0 Eco Mode 1 Maximum Performance Mode Table 4: Supported CFG_GPS0 settings (LEA-5Q) The CFG_GPS0 pin is shared with the SPI Clock pin. When using Eco Mode and SPI, pull CFG_GPS0 low during startup and then release it.. Power Management Considerations with designs Application note Changing Configuration GPS.G5-CS B Page 13

14 Related Documents [1] LEA-5 Data Sheet, Docu. No GPS.G5-MS [2] TIM-5 Data Sheet, Docu. No GPS.G5-MS [3] NEO-5 Data Sheet, Docu. No GPS.G5-MS [4] U-blox 5 ICs Data Sheet, Docu No GPS.G5-X-06063D [5] Protocol Specification, Docu. No GPS.G5-X All these documents are available on our homepage ( For regular updates to u-blox documentation and to receive product change notifications please register on our homepage. Power Management Considerations with designs Application note Related Documents GPS.G5-CS B Page 14

15 Contact For further info, please contact us: Headquarters u-blox AG Zuercherstrasse 68 CH-8800 Thalwil Switzerland Phone: Fax: Offices North, Central and South America u-blox America, Inc Campus Commons Drive Suite 310 Reston, VA USA Phone: +1 (703) Fax: +1 (703) Regional Office West Coast: Phone: +1 (703) Fax: +1 (703) Technical Support: Phone: +1 (703) Europe, Middle East, Africa u-blox AG Zuercherstrasse 68 CH-8800 Thalwil Switzerland Phone: Fax: Technical Support: Phone: Asia, Australia, Pacific u-blox Singapore Pte. Ltd. 435 Orchard Road #17-01, Wisma Atria, Singapore Phone: Fax: Support: Regional Office China: Room No. 65 Fuxing Road Beijing, , China Phone: Fax: Support: Regional Office Japan: 6F Akasaka Yoko Building, 4-8-6, Akasaka Minato-ku Tokyo Japan Phone: Fax: info_jp@u-blox.com Support: support_jp@u-blox.com Regional Office Korea: Room 501, Gyeong Hui Building , Samseong-Dong, GangNam-Gu, Seoul, Korea Phone: Fax: info_kr@u-blox.com Support: support_kr@u-blox.com Regional Office Taiwan: Room 305 3F, #181, ZouTze Street Neihu Dis. Taipei, Taiwan Phone: Fax: info_tw@u-blox.com Support: support_tw@u-blox.com Power Management Considerations with designs Application note Contact GPS.G5-CS B Page 15