Minimum VDD for USB device

[jh0]

What is minimum voltage for MKL27Z64VLH4 (or similar M0+) to work as USB device? Is it possible to use it as 1.8V like on attached picture?

If I understood right, during working as crystalless USB device, internal precise 48 MHz clock can be used also as source for master (or for other peripherals) clock. 

I found FlexIO AN for UART, I2C, SPI, PWM. Is there any FlexIO SWD (master) open source example?

[bobpaddock]

If communicating via USB the minimum voltage per the standard is 4.2V for VBus.

http://www.usb.org/developers/docs/whitepapers/power_delivery_motherboards.pdf

I know you said Device, understating the Host end is important as well.

http://www.usb.org/developers/compliance/electrical_tests/USB_2_0_Electrical_Compliance_Specificatio...

See http://www.usb.org for others.

[miduo]

Hi,

yes, the internal USB regulator powers the USB transceiver or the MCU itself (depending on the application). 
in this case the supply voltage for chip could be 1.8V.