2015-07-21 01:20 PM
I am running the stm32f407 at 1.85V and was wondering if it would be possible to get USB working at this operating voltage. I've pulled up the d+ line to Vbus but cannot get proper enumeration. I believe as long as the differential signal is 100-200mV on the receiving side it should still work. Even with a very short USB cable still no enumeration. Is some kind of level translator or usb signal repeater my only option? Thanks.
2015-07-21 01:33 PM
The manual for your part says 3.0V minimum VDD, and it can get down to 2.7V with degraded electrical characteristics.
I think these are requirements of the transceiver cell itself, so I don't think you're going to be able to fudge things externally.2015-07-21 01:56 PM
Thanks. I read that minimum voltage in the datasheet as well but they explicitly said 'OTG USB FS' so I thought there may still be a chance.