maximum ratings for LIN

[j_kleinen]

Hi,

we are using S912ZVML31F1WKF in a 80W BLDC application with LIN communication and I have a question about the LIN Interface.

What would happen if the Signal Level is higher than the supply voltage? We have an universal test equipment which provides the test LIN interface but this device is driven with 24V and our DUT is only powered with 8 to 16V (Voltage range for 12V car battery) Could this constellation lead into bus failure or even device damage?

Thank you for your help,

Jakob Kleinen

[j_kleinen]

Hi Daniel,

thanks for your help. So far we didn't experience any timing problems but we will change our equipment to prevent problems in the future.

Regards

Jakob

[danielmartynek]

Hi Jakob,

It should not damage the MCU, because the LIN standard specifies such a condition as loss of supply.
Under this condition, the input injection (or leakage) current in the recessive state needs to be very limited by the LIN PHY in order to not disturb the LIN communication for other modules on the bus.
Please see Table D-1, S12ZVM RM rev.2.13

However, there can be some issues.
Depending on the total resistive load on the bus, the MCU can detect overcurrent in the dominant state.

Also, the LIN PHY slew rate is a function of the supply voltage, e.g. the higher the supply, the faster the rate is in order to have a fixed timing for the slopes.
Although the bus voltage is higher, the LIN PHY operates at VLINSUP voltage and might not use so appropriate timing, the transmitter may reserve too much time for the slopes.

Regards,
Daniel