u-blox TOBY-L4 Series System Integration Manual

Contents

TOBY-L4 series - System Integration ManualUBX-16024839 - R04 Design-inPage 100 of 1432.6.6 RGMII interfaceThe RGMII interface is not supported by the "50" product version.2.6.6.1 Guidelines for RGMII circuit designTOBY-L4 series modules include an Ethernet Media Access Control (MAC) block supporting up to 1 Gbit/s datarate via a Reduced Gigabit Media-Independent Interface compliant with the RGMII Version 1.3 specification [7]and the RMII Revision 1.2 specification [8].The module represents an Ethernet MAC controller, which can be connected to a compatible external Ethernetphysical transceiver (PHY) chip to provide communication over Ethernet as illustrated in Figure 59.Recommended compatible Ethernet PHY chips are: Marvell 88E1510 Marvell 88E1512TOBY-L4 seriesEthernetMACRGMII ConnectorEthernetPHYUnshielded Twisted PairFigure 59: RGMII interface application circuit block diagramThe ESD sensitivity rating of RGMII interface pins is 1 kV (HMB according to JESD22-A114). A higherprotection level could be required if the lines are externally accessible and it can be achieved by mountinga very low capacitance ESD protection (e.g. Tyco Electronics PESD0402-140 ESD) close to the accessiblepoints.If the RGMII interface pins are not used, they can be left unconnected on the application board.2.6.6.2 Guidelines for RGMII layout designThe RGMII / RMII interface requires the same considerations regarding electro-magnetic interference as any otherhigh speed digital interface.Keep the traces short, avoid stubs and avoid coupling with RF lines / parts or sensitive analog inputs, since thesignals can cause the radiation of some harmonics of the digital data frequency.Consider the usage of low value series damping resistors to avoid reflections and other losses in signal integrity,which may create ringing and loss of a square wave shape.