u-blox LEA-4R System Integration Manual And Reference Design

Contents

u-blox LEA-4R System Integration Manual And Reference Design Manual pdf 11 page image

your position is our focusSchematic Leave the RESET_N pin open if not used. Don’t drive it high! Leave BOOT_INT pin open if not used for firmware update. Plan use of 2nd interface for firmware updates or as a service connector.2.2 TIM-4R/LEA-4R DesignLEA-4RTIM-4ROdometerOptionalDirectionTurn Rate SensorFiler, opto-couplersFiler, opto-couplers3V levels3V levelsSPEEDFWDSPIRATELow-Passfilter(MOSI) leave openDigitalTempSensorADGNDRF_INCoaxialconnectorRF_IN VANTV_ANTAADET_NVCC_REFV_BATVCC (3V)GNDGNDVDD18_OUTTxD1 / TxD2RxD1 / RxD2USBUSBTIMEPULSERESET_NOptionalOptional(BOOT_INT) leave openOpen circuitdetection(optional)GyroBackupSupplyFigure 5: Block Schematic of a complete LEA-4R / TIM-4R Design2.2.1 Forward / Backward IndicationUse of the forward / backward indication signal FWD is optional but strongly recommended for good deadreckoning performance. Connect to VDD18_OUT (1.8V) if not used.You need to check the voltage levels and the quality of the vehicle signals. They may be of different voltagelevels, for example 12V nominal with a certain degree of variation. Use of optocouplers or other approved EMIprotection and filtering is strongly recommended.2.2.2 Odometer / SpeedpulsesDR receivers use signals from sensors in the car to establish the velocity and distance traveled. These sensors arereferred to as the odometer and the signals can be designated odometer pulses, speedpulses, speed ticks, wheelpulses or wheel ticks. These terms are often used interchangeably which can sometimes lead to confusion. Forthe sake of consistency, in this document we will be referring to these signals as speedpulses.2.2.3 Power Supply for Gyroscope, Temperature Sensor and A/D ConverterThe Gyro and the A/D-Converter are especially sensitive to voltage drop and ripple. Therefore a clean powersupply must be designed, which is, for example, not affected from current spikes produced by the GPS module.LEA-4R / TIM-4R - System Integration Manual / Reference Design Design-InGPS.G4-MS4-05043 Page 11