I need to protection data lines of a PIC32 micro-controller (SPI and parallel) running at ~10 MHz, from shorting to ground/Vcc or mis-wiring.
I usually (in low speeds) use series resistors to limit current and it worked well, but of course this does not work now because of the speed.
I am thinking to use line buffer/inverter (something like 74LVC04) this will save the MCU but the buffer will get damaged.
I searched many logic families (ACT , HCT , LVC etc..), but none provide short circuit protection.
I there a better solution?
Edit After Comments: This is a development board for testing and validation, due to coding mistakes pins can be configured incorrectly . or mis-wired , connecting MCU output to target output instead of input.
Edit #2: A PTC (0603L004) might be a solution however it is slow !
Best Answer
CMOS drivers have an inherent current limit set by the drain-source ‘on’ resistance of the output driver FETs, Rds(on). You can infer this from the datasheet based on Vo(h) and Vo(l) for a given output current.
As an example, the PIC32 datasheet list Vo(l) as 0.36V at 6mA, which corresponds to an Rds(on) 60 ohms. That's kind of a weak driver. Shorting it to 3.3V would give 55mA, which is more than the datasheet allows (16mA), a pretty tight limit. That said, a short on one pin won't necessarily damage the part.
The bigger problem often is ESD damage. Stuff that goes off board can benefit from additional TVS diodes to increase the ESD robustness.