The LMR3650x is in active mode whenever the EN/UVLO pin is above V_EN-VOUT, V_IN is high enough to satisfy V_{IN_R}, and no other fault conditions are present. The simplest way to enable the operation is to connect the EN/UVLO pin to V_IN, which allows self start-up when the applied input voltage exceeds the minimum V_{IN_R}.

In active mode, depending on the load current, input voltage, and output voltage, the LMR3650x is in one of five modes:

• Continuous Conduction Mode (CCM) with fixed switching frequency when load current is above half of the inductor current ripple
• AUTO Mode - Light Load Operation: PFM when switching frequency is decreased at very light load
• FPWM Mode - Light Load Operation: Continuous Conduction Mode (CCM) when the load current is lower than half of the inductor current ripple
• Minimum on-time: At high input voltage and low output voltages, the switching frequency is reduced to maintain regulation.
• Dropout mode: When switching frequency is reduced to minimize voltage dropout.