The following layout example shows how the FPC402 can be placed underneath a stacked SFP cage, on the opposite side of the PCB. In this example, the FPC402 is being used to control four ports: two SFP ports and two QSFP ports. In addition, the FPC402 is using two of its GPIO pins to control a TPS2556 power distribution switch which is placed beneath the QSFP cage. Note that there are multiple ways to route the low-speed control signals and I2C signal between the cages and the FPC402. This example uses two inner layers to accomplish this routing.

Figure 11-1 Layout Example