u-blox LEA-5 Series Hardware Manual

Contents

u-blox LEA-5 Series Hardware Manual Manual pdf 10 page image

LEA-5, NEO-5, TIM-5H - Hardware Integration ManualGPS.G5-MS5-09027-A2 Released Hardware descriptionPage 10 of 68specification) for a short time. In order to define a battery capacity for specific applications the sustained powerfigure shall be used.When switching from backup mode to normal operation u-blox 5 modules must charge the internalcapacitors in the core domain. This can result in certain situations result in a significant current draw. Forlow power applications using Power Save and backup modes it is important that the power supply orlow ESR capacitors at the module input can deliver this current/charge.1.3.1.2 V_BCKP - –ackup batteryIn case of a power failure on pin VCC, the real-time clock and backup RAM are supplied through pin V_BCKP.This enables the u-blox 5 receiver to recover from a power failure with either a Hotstart or a Warmstart(depending on the duration of VCC outage) and to maintain the configuration settings. If no backup battery isconnected, the receiver performs a Coldstart at power up.If no backup battery available connect the V_BCKP pin to GND (or VCC).As long as VCC is supplied to the u-blox 5 receiver, the backup battery is disconnected from the RTC and thebackup RAM in order to avoid unnecessary battery drain (see Figure 2). Power to RTC and BBR is supplied fromVCC in this case.VCCV_BCKPVoltageSupervisorModule Voltage SupplyRTC and Battery Backup RAM (BBR)J1Figure 2: Backup Battery and Voltage1.3.1.3 VDD_USB - –SB interface power supply (LEA-5, NEO-5)VDD_USB supplies the I/Os of the USB interface. If the USB interface is not used, the VDD_USB pin must beconnected to GND. For more information regarding the correct handling of VDD_USB see section 1.5.2.11.3.2 Operating modesu-blox 5 modules with FW 6.00 have 2 continuous operating modes (Maximum Performance and Eco) and 1intermittent operating mode (Power Save mode). Maximum Performance mode freely uses the acquisitionengine, resulting in the best possible TTFF, while Eco mode optimizes the use of the acquisition engine to deliverlower current consumption. At medium to strong signals, there is almost no difference for acquisition andtracking performance in these modes.1.3.2.1 Maximum Performance modeIn Maximum Performance mode, u-blox 5 receivers use the acquisition engine at full performance to search forall possible satellites until the Almanac is completely downloaded.As a consequence, tracking current consumption level will be achieved when:A valid GPS position is fixedAlmanac is entirely downloadedEphemeris for all satellites in view are valid