STM32L072RBT6 minimum voltage for USB device

josh novi · ‎2017-09-11

Posted on September 11, 2017 at 21:20

Can it work as USB device on 1.8V (VDD), with separate regulator for 3.3V on VDD_USB?

How pulling of D+ over 1.5k to 3.3V is done (internaly maybe)?

If there is other performance limitation regarding working on low voltage (1.8V)?

If USB internal clock generator (crystalless) can be used as USB device 32 MHz CPU/buss precise clock source?

Tesla DeLorean · ‎2017-09-12

Posted on September 12, 2017 at 11:21

Sure the data sheet or reference manual talk about voltage vs speed and flash wait states, etc.

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josh novi · ‎2017-09-18

Posted on September 18, 2017 at 13:39

There is no problem with flash wait states, because function can be copied to RAM and executed there.

And what is this (from datasheet)?

'Note: VDD_USB value does not dependent on VDD and VDDA. However, VDD_USB must be the last

supply to be delivered to the device and the first to be switched off. When the three power

supplies are shut down, if VDD_USB remains active for a short period of time and VDDA/VDDIO

fall below the functional range, the device is not be damaged.

The device is still functional when VDD_USB is switched off.'

Why user/designer need to handle this, why this is not resolved by chip itself.

What is the problem with VDD / VDD_USB power on / off order? How long is 'a short period of time'?