I'm building a USB 2.0 bus-powered STM32F429-based audio device that is able to run in a stand-alone mode from a phone charger, or running as a USB device when connected to a computer. To comply with the USB spec, the device should not consume more than 2.5mA when in suspend mode.

I want to be able disconnect power to the led driver (25 mA idle), a SDRAM chip (also 25 mA) and a oscillator using MIC94070 high side switches, as well as disabling the boost-regulator that powers the analog part. This will leave me running only with the MCU and USB PHY.

Are there any ceveats to this approach? I can think about avoiding back-powering the chips by pulling the gpio's low first before disabling the switches, but that's about it :)

To help conserve power, I've already optimised the number and values of pull-down resistors and chosen low-Iq regulators.

  • 2
    \$\begingroup\$ Are you storing any data in the SDRAM that needs to survive through sleep? \$\endgroup\$ Jun 20, 2019 at 20:38
  • \$\begingroup\$ No the SDRAM isn't used in device mode, so no worries there. \$\endgroup\$ Jun 20, 2019 at 20:42


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