straightforward approaches and stretches to the complicated and expensive ones. This is not a
complete list. There exist other solutions that are not discussed here. Some backfeeding
countermeasures are specific to an interface. Therefore, following the reference schematics is
advised.
3.7.5.1 Avoid Multiple Power Domains
The best solution for preventing backfeeding is trying to avoid having different power domains. Try
to use the same voltage for the IO rail and the peripheral devices. For some Colibri modules, the
IO rail is identical to the module's main power supply (VCC). For such modules, it is advised to use
the same power source also for the peripherals.
Figure 40: Keep the peripherals on the same Domain
3.7.5.2 Avoid Driving Outputs High
Backfeeding can be prevented by ensuring the output pin is not driven high while the IO rail of the
input side is powered off. This is a standard solution for preventing backfeeding from the module
to peripheral devices. Before disabling the peripherals' power rails (for example, when going into
sleep mode), the software makes sure that the output signals are either driven low or set into a
high-Z mode. Some SoC pins have internal pull-up resistors. It is also important to switch off the
pull-up resistors and optionally enable the pull-down resistor.
Figure 41: Make sure outputs are not driven high
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