u-blox TOBY-L4 Series System Integration Manual

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TOBY-L4 series - System Integration ManualUBX-16024839 - R04 Design-inPage 107 of 1432.8.1.2 Guidelines for analog audio downlink path circuit designGuidelines for connecting an external low-power receiver / speakerFigure 63 and Table 47 show an application circuit connecting the downlink path of the analog audio interfaceof TOBY-L4 series modules to a low-power receiver / speaker: A 16  receiver / speaker is connected to the analog audio downlink path of the moduleAs in the example circuit in Figure 63 and Table 47, the following general guidelines are recommended for thedesign of an analog audio circuit connecting a low-power receiver / speaker: Connect the SPK_P and SPK_N analog downlink outputs directly to the receiver / speaker (which resistancerating must be greater than 14 ). Provide suitable parts on each line connected to the receiver / speaker as noise and EMI improvements, tominimize RF coupling, according to EMC requirements of the custom application.o Mount a 27 pF bypass capacitor (e.g. Murata GRM1555C1H270J) from each speaker line to the solidground plane (C1 and C2 capacitors in Figure 63). Provide additional ESD protection (e.g. Bourns CG0402MLE-18G varistor) if the analog audio lines will beexternally accessible on the application device, according to the EMC/ESD requirements of the customapplication. Mount the protection close to an accessible point of the line (D1 and D2 in Figure 63).TOBY-L4 seriesSPK_PSPK_ND1C1 C2SPKSpeakerConnectorJ1D2Figure 63: Application circuit connecting the analog audio interface to a low-power speakerReference Description Part Number – ManufacturerC1, C2 27 pF Capacitor Ceramic C0G 0402 5% 25 V GRM1555C1H270JA01 – MurataD1, D2, Low Capacitance ESD Protection CG0402MLE-18G - BournsJ1 Speaker Connector Various ManufacturersSPK 16  Speaker Various ManufacturersTable 47: Example of components for connecting the analog audio interface to a low-power speaker