power supply for PSoC4

[WCH]

hello，I‘m user of  CY8C4014LQI-421_16-QFN. I have two questions about it .

• about the power supply mode.

"There are two distinct modes of operation. In Mode 1, the supply voltage range is 1.8 V to 5.5 V (unregulated externally; internal regulator operational). In Mode 2, the supply range is1.8 V ±5% (externally regulated; 1.71 to 1.89, internal regulator bypassed)."

I want to know that which mode has stronger robustness?If I use the mode 2,what  the pitfalls might it has?

• about the I2C 

If I power the VDD=3.3V .what the high threshold and low threshold are?

3.3V*0.7and3.3V*0.3?

OR  1.8V*0.7and1.8V*0.3?

thanks!

[Len_CONSULTRON · Accepted solution]

WCH,

The external voltage you need to supply is going to be highly dependent on the voltage requirements of the external peripherals you are going to interface to.   For example you mentioned I2C.  Most I2C external peripherals require 5V or 3.3V.  Some allow for 2.7V and 1.8V but you have to check the I2C peripheral datasheet.

When you are interfacing to other peripheral circuits, the  power supply you use to power VDD, will basically determine VDDIO which is the highest voltage used to signal to the external peripherals. 

Note: If you are planning to use a PSoC6, the maximum voltage to VDD is 3.3V.