L9613B: K-line voltage limits and protection with VS powered off
We are designing a 12V BMW diagnostic adapter using L9613B013TR.
VS is supplied from a reverse-protected, overvoltage-disconnected battery rail. VCC is switched 5V. K connects to OBD pin 7 through a 10-ohm pulse-rated resistor, with ESD2CAN24DBZRQ1 protection at the connector. A switched 510-ohm pull-up and optional pin 7-8 PhotoMOS bridge are on the bus side. No supply-rail steering clamp is used.
The September 2013 Rev 3 absolute-maximum table bounds K by VS, while the functional description discusses beyond-VS operation and high impedance when VS is missing. Please clarify:
1. What positive and negative K voltages, continuous and transient, are permitted with VS=0, VS open, or VS=9-16V, with VCC either 0 or 5V? Include permissible injection/clamp currents and temperature limits.
2. What external protection network do you recommend for these conditions?
3. Can you provide guaranteed propagation-delay asymmetry/pulse-width distortion and load limits supporting 115200 baud? The 13us switching maxima alone do not establish the required receive timing margin.
Datasheet: https://www.st.com/resource/en/datasheet/l9613.pdf
An optional SMF20A secondary clamp is DNP and is not part of the fitted circuit. It has not been accepted for sustained negative-line faults.