Looking for the simple way to protect output pin of microcontroller with VCC 1.8V - 3.3V, from VPP 6.5V that will be applied sometimes, only during high state (1.8V - 3.3V) on pin output. Easiest way will be to put few kohm resistor between, but this is not possible because of high speed on PIO (6 MHz). Driving current on micro pin is few mA. I guess that isolation can be done with some fast low drop diode like MBR0450.
All things that I can find by google are related to ESD, and 3.3V / 5V glue logic.
Just for further clarification. This is only output pin / signal, and 6.5 V is applied to line by FET under same micro control. Changing 1.8V / 3.3V to 6.5V must be continuous (logic hi) without glitches. Only solution that I know (lower frequency) is...
but instead of 1G is direct pin connection. However, micro is connected over flat / ribbon cables to other side and with 150R and 1 meter cable length with 6 MHz signal is working just fine. Don't want to be forced to reduce cable length because of VCC/VPP interface, so looking for some better diode than LL103A, or some other design, whatever. Maybe somebody know why on picture 2k7 is used, and not for example 10k. On other side signal is grounded over 50k resistor.