I'm designing an isolation circuit for SPI communication (CLK, MOSI, CS and MISO) thus I'm using an ADuM6401 (isoPower insulator with 3ch out and 1ch in).
I want use it with Vdd1=5V and Viso=3.3V. The SPI signals (on both sides) will work with 0-3.3V logic.
What are the logic high input threshold? The datasheet rev.A on table 13 says, for the logic high: "0.7 × VISO or 0.7 × VDD1".
- This means that I must consider the lower value between 0.7*VISO=0.7*5=3.5V and 0.7*VDD1=0.7*3.3=2.31V, that is 2.31V?
- Or I must consider that the threshold are 0.7*VISO for the "left side signals" and 0.7*VDD1 for the "right side signals"
Thank you all!