Integration Manual

Table Of Contents
TOBY-L3 series - System Integration Manual
TSD-19090601 - R13 System Integration Manual Page 112 of 143
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.
2.7 eMMC interface
The eMMC interface is not supported by the "0x" product feature versions.
2.7.1 Guidelines for eMMC circuit design
TOBY-L3 series modules include a 4-bit embedded Multi-Media Card interface compliant with JESD84-B451
Embedded Multimedia Card (eMMC) Electrical Standard 4.51 [9], which can be handled by means of the
open CPU API.
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_CLK
clock line and the MMC_CMD command line, to increase the rise time on the signals so as to compensate
for any capacitance on the board, even if not strictly required.
Do not apply loads which might exceed the limit for the maximum available current from V_MMC
supply (see TOBY-L3 series Data Sheet [1]) as this can cause malfunctions in the internal circuitry.
The ESD sensitivity rating of eMMC interface pins is 1 kV (HMB according to JESD22-A114). A higher
protection level could be required if the lines are externally accessible and it can be achieved by
mounting a very low capacitance ESD protection (e.g. Tyco Electronics PESD0402-140 ESD) close to the
accessible points.
If the eMMC interface pins are not used, they can be left unconnected on the application board.
2.7.2 Guidelines for eMMC layout design
The eMMC interface requires the same considerations regarding electro-magnetic interference as any other
high speed digital interface.
Keep the traces short, avoid stubs and avoid coupling with RF lines / parts or sensitive analog inputs, since
the signals 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.