SNOSDE8A July 2023 – September 2023 LM74912-Q1
PRODUCTION DATA
Table 9-1 summarizes the design parameters that must be known for designing an automotive reverse battery protection circuit with overvoltage cut-off. During power up, inrush current through MOSFET Q2 needs to be limited so that the MOSFET operates well within its SOA. Maximum load current, maximum ambient temperature and thermal properties of the PCB determine the RDSON of the MOSFET Q2 and maximum operating voltage determines the voltage rating of the MOSFET Q2. Selection of MOSFET Q2 is determined mainly by the maximum operating load current, maximum ambient temperature, maximum frequency of AC super imposed voltage ripple and ISO 7637-2 pulse 1 requirements. overvoltage threshold is decided based on the rating of downstream DC/DC converter or other components after the reverse battery protection circuit. A single bi-directional TVS or two back-back uni-directional TVS are required to clamp input transients to a safe operating level for the MOSFETs Q1, Q2 and LM74912-Q1.