Hi,
I'm trying to use zener diodes to protect the inputs to an IO driver chip (Microchip MCP23017)
The IO chip runs off 3.3V and cannot accept any inputs higher than this; however, all of my inputs are at 5V.
Attached is a schematic for my protection circuit arrangement. Pins 1-8 on CONN1 are where 5V inputs will be introduced and I1-I8 is the connection to the IO driver chip. As can be seen, each input has a 3.3V zener diode and 10K resistor placed in parallel with it.
My problem is that this arrangement does not seem to work! The IO driver chip still gets 5V at its inputs (I1-I8)
Does anyone have any ideas as to what I'm doing wrong?
Thanks
The datasheet for the 3.3V zeners I'm using is located here:
---docs-europe.origin.electrocomponents.com/webdocs/0dad/0900766b80dad746.pdf---
I'm trying to use zener diodes to protect the inputs to an IO driver chip (Microchip MCP23017)
The IO chip runs off 3.3V and cannot accept any inputs higher than this; however, all of my inputs are at 5V.
Attached is a schematic for my protection circuit arrangement. Pins 1-8 on CONN1 are where 5V inputs will be introduced and I1-I8 is the connection to the IO driver chip. As can be seen, each input has a 3.3V zener diode and 10K resistor placed in parallel with it.
My problem is that this arrangement does not seem to work! The IO driver chip still gets 5V at its inputs (I1-I8)
Does anyone have any ideas as to what I'm doing wrong?
Thanks
The datasheet for the 3.3V zeners I'm using is located here:
---docs-europe.origin.electrocomponents.com/webdocs/0dad/0900766b80dad746.pdf---