XS1-U8A with VSUP = 3.3 V
Posted: Tue Aug 26, 2014 11:17 pm
Hi all - just a few quick questions when operating the XS1-U8A with the VSUP supply held at 3.3 V and not 5.0 V:
1) Are there any requirements when operating the device with VSUP held at 3.3 V (configuration pin as on some FPGAs, etc.), or is tying VSUP to a 3.3 V supply simply enough?
2) Page 23 of the data sheet states that all supplies most be brought up monotonically. Does this mean I cannot tie the VSUP and VDDIO supplies together from the same supply when operating in 3.3-V mode? Do they need to be sequenced in any special fashion? Can I not simply relax this requirement and tie the two together?
3) The data sheet implies that running VSUP at 3.3 V reduces efficiency - has this been quantified in any fashion?
4) In 3.3-V mode, no 5-volt supply is present. The data sheet states the USB_VBUS pin must be connected, but this seems like an ESD diode forward-bias hazard. Can the USB_VBUS pin tolerate VBUS-level voltages, or must there be a divider between the raw VBUS supply and the USB_VBUS pin?
Thanks in advance.
1) Are there any requirements when operating the device with VSUP held at 3.3 V (configuration pin as on some FPGAs, etc.), or is tying VSUP to a 3.3 V supply simply enough?
2) Page 23 of the data sheet states that all supplies most be brought up monotonically. Does this mean I cannot tie the VSUP and VDDIO supplies together from the same supply when operating in 3.3-V mode? Do they need to be sequenced in any special fashion? Can I not simply relax this requirement and tie the two together?
3) The data sheet implies that running VSUP at 3.3 V reduces efficiency - has this been quantified in any fashion?
4) In 3.3-V mode, no 5-volt supply is present. The data sheet states the USB_VBUS pin must be connected, but this seems like an ESD diode forward-bias hazard. Can the USB_VBUS pin tolerate VBUS-level voltages, or must there be a divider between the raw VBUS supply and the USB_VBUS pin?
Thanks in advance.