PROTECT line is powered by signal inputs
Input signals are protected by two protection diodes. This is okay! However, the upper protection diode is clamped to the I/O over-voltage protection bias circuit build around a zener diode which is fed by 12 V. This means that the 12V line is indirectly powered by the input signals when the 12V is absent which typically is the case at power-up. The above issue causes trouble when the DIO is plugged onto a board that has a power converter with under voltage lockout protection (UVLO) since these converters reset their UVLO fault latch when the input voltage dropped under the UVLO threshold.
- Plug the DIO but do not connect DIO input signals.
- Power the system
- Plug input signals into DIO.