SNVSBJ0A December 2019 – June 2020 LM5170
The LM5170 includes a circuit to detect a MOSFET switch short-circuit failure during start-up. If a MOSFET drain and source are found shorted, the LM5170 pulls down the nFAULT pin to flag the fault, and the controller remains in an OFF state. This feature prevents the LM5170 from starting with a short-circuit-failed MOSFET, thereby preventing catastrophic failures.
The LM5170 also integrates a control circuit to control the circuit breaker. As shown in Figure 33, the circuit breaker consists of a pair of back-to-back MOSFETs. When the breaker is off, the current path between the HV-Port and LV-Port is cut-off so as to prevent possible catastrophic failures.
The failure detection function must be deactivated if the circuit breaker is not present, or if the circuit breaker FETs are not controlled by the LM5170.