I'm doing a layout for someone who has asked for a USB interface on a micro that is running at 2.5V. As far as I can tell after researching this, you can't run USB down to 2.5V. So, I did a bit of digging aorund for a level shifter and found this:
On first glance it looks like just what I need. I can run the high voltage side from a 3V3 reg off the USB 5V and the processor side can run off 2V5.
However, the data sheet says:
The TXS0202 is a 2-bit voltage level translator optimised for use in Interchip USB (IC-USB) applications.
It has a diagram of it interfacing between a micro and an HD SIM card.
So, my questions are:
- Is it right the USB will not work correcty running the micro at 2.5V?
- Will the TXS0202 work if it's connected to a cabled interface on the high voltage side?
- If point 2 is no, can I actually do what I need to? Are there simple devices that will level shift for cabled interfaces?
I would have throught there must be devices to do this, there must be scores of examples of micros running at less then 3V3 that have a USB interface. I cannot find anything other than three devices that all say they are for "inter chip" interfaces. I appreciate inter chip doesn't specifically say on the same board, but the typcial application diagrams seem to imply that - or at least that's what I'm inferring.