2.2.2.3 PCIe x1 Device-Down Schematic Example
Device-Down means that the PCIe device is soldered directly to the carrier board. The decoupling
capacitors for the RX lanes (TX from the device) need to be placed on the carrier board. As the
capacitors for the TX lanes are located on the Apalis module, no additional capacitors should be
place on the TX lines. The reference clock lines do not need decoupling capacitors.
Figure 10: PCIe Device-Down block diagram
The schematic diagram shown below is an example of a device-down design of a gigabit Ethernet
controller. Please be aware that the TX lane from the module needs to be connected to the RX
input of the controller. The RX lane from the module needs to be connected to the TX output of the
controller. Check your device carefully to determine whether it needs this crossing or not.
Figure 11: PCIe Device-Down example schematic
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