u-blox LEA-5 Series Hardware Manual

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u-blox LEA-5 Series Hardware Manual Manual pdf 47 page image

LEA-5, NEO-5, TIM-5H - Hardware Integration ManualGPS.G5-MS5-09027-A2 Released Design-inPage 47 of 68Small passive antennas (<2 dBicand performance critical)Passive antennas (>2 dBic orperformance sufficient)Active AntennasARF_INGPSReceiverLNA BLRF_INGPSReceiver CDRF_INGPSReceiverLNA with appropriate ESD ratingFigure 38: ESD PrecautionsProtection measure A is preferred due to performance and protection level considerations.2.7.4 Electrical Overstress (EOS)Electrical Overstress (EOS) usually describes situations when the maximum input power exceeds the maximumspecified ratings. EOS failure can happen if RF emitters are close to a GPS receiver or its antenna. EOS causesdamage to the chip structures.If the RF_IN is damaged by EOS, it‖s hard to determine whether the chip structures have been damaged by ESDor EOS.2.7.5 EOS protection measuresEOS protection measures as shown in Figure 39 are recommended for any designs combining wirelesscommunication transceivers (e.g. GSM, GPRS) and GPS in the same design or in close proximity.Small passive antennas(<2 dBic and performancecritical)Passive antennas (>2 dBic orperformance sufficient)Active Antennas (without internal filterwhich need the module antenna supervisorcircuits)DRF_INGPSReceiverLNAGPSBandpassFiltler ERF_INGPSReceiverLGPSBandpassFiltler FRF_INGPSReceiverLGPSBandpassFiltlerC CL LLNA with appropriate ESDrating and maximum inputpowerGPS Bandpass Filter: SAW orCeramic with low insertion lossand appropriate ESD ratingFigure 39: EOS and ESD Precautions2.7.6 Electromagnetic interference (EMI)Electromagnetic interference (EMI) is the addition or coupling of energy released from any RF emitting device.This can cause a spontaneous reset of the GPS receiver or result in unstable performance. Any unshielded line or