Is it good idea to connect my microcontroller to LIN bus with logic level shifter (5 <=> 12 V) instead of factory LIN transceiver (MCP2003, TJA1020, etc.)?
As I understand, LIN transceiver just converts logic level UART signal to 12V LIN bus and vise versa. The same thing is possible to do with logic level shifter or voltage divider on resistors. Are there any gaps in these approaches?
Best Answer
A LIN bus tranceiver is basically at its core nothing more than just a level shifter. But let's explore the gaps then.
LIN tranceiver chip is specifically made according to LIN bus specifications. These specifications include specific voltage thresholds for interpreting logic levels, specific capasitive and resistive load, specific signal rise/fall times, specific overvoltage and undervoltage protection, short-circuit and overcurrent protection, ESD protection etc, just to make sure at all devices work properly within the agreed limits for the whole bus and each tranceiver.
If you just take a random logic level shifter, it won't have those features. If you connect it to a LIN bus in your car, and if it gets damaged due to the harsh electrical environment, it could do serious damage to other devices on the bus too.
So no, it definitely is not a good idea to connect to a LIN bus without a LIN tranceiver.