u-blox TOBY-L4 Series System Integration Manual

Contents

TOBY-L4 series - System Integration ManualUBX-16024839 - R04 Design-inPage 101 of 1432.7 eMMC interfaceThe eMMC interface is not supported by the "50" product version.2.7.1.1 Guidelines for eMMC circuit designTOBY-L4 series modules include a 4-bit embedded Multi-Media Card interface compliant with JESD84-B451Embedded Multimedia Card (eMMC) Electrical Standard 4.51 [9], which can be handled by means of the uCPUAPI.The eMMC interface can be connected to an external eMMC / SD memory as defined by the standard.Pull-up resistors can be added on MMC_D0, MMC_D1, MMC_D2 and MMC_D3 data lines, the MMC_CLKclock line and the MMC_CMD command line, to increase the rise time on the signals so as to compensate forany capacitance on the board, even if not strictly required.The ESD sensitivity rating of eMMC 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 eMMC interface pins are not used, they can be left unconnected on the application board.2.7.1.2 Guidelines for eMMC layout designThe eMMC interface requires the same considerations regarding electro-magnetic interference as any other highspeed 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.