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Take a look at this schematic, especially on the USB OTG part of it.

It uses a SY6280 "5.5V, 2A Low Loss Power Distribution Switch" as a means to control the 5V USB-bus power.

I was wondering if it would be a good idea to implement this sort of thing on all my peripherals, in order to enable them or disable them according to my power requirements e.g SD card, sensors, relays etc.

My design features a 18650 battery to power the device when AC mains is out, like a UPS. Would you consider this approach effective as a means of power management during lost AC mains, in order to power only the necessary blocks of my design?

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Cutting power to peripherals when they are not needed can definitely save power. But there are some things to be aware of.

First, if you have pins connecting from the main processor to the peripheral, all those pins have to be forced low or undriven when the peripheral is de-powered. If the lines have pullups, the pullups have to be connected to the same VCC that you are switching off. For this reason, it may not be practical to de-power peripherals which use I2C, for example, unless you are de-powering ALL of the I2C peripherals at the same time.

On boards with a VCC plane, using switched power can complicate component placement and routing.

Some peripherals require configuration or initialization after they power up. And the driver code on the host processor may not realize that the peripheral has lost its configuration. So there can be some software complication involved in re-configuring a peripheral each time power is cut and then restored.

None of this is intended to talk you out of it. These are just things to keep in mind.

I have done this before, but usually I don't use a dedicated load switch IC. I just use one or two MOSFET's, depending on details.

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  • \$\begingroup\$ Thanks for the reply and the recommendations, looks like I have a lot to think about. \$\endgroup\$
    – geocheats2
    Commented Feb 27, 2021 at 10:49
  • \$\begingroup\$ @geocheats2 Also, some peripherals can be put in standby/deep sleep, without having to power them off. These peripherals would typically consume a few µA in this state, or even less. This may be low enough for your application, and using this rather than implementing multiple power domains typically makes for a simpler design. So you may consider this. Check the datasheets of your peripherals, check their total consumption in sleep mode, and check the uptime you need for your application. \$\endgroup\$
    – dim
    Commented May 4, 2021 at 12:10

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