The LM6x4xx is in active mode when the following occurs:

• The EN pin is above V_EN.
• V_IN is above V_EN.
• V_IN is high enough to satisfy the V_IN minimum operating input voltage.
• No other fault conditions are present.

See Section 8.3 for protection features. The simplest way to enable the operation is to connect EN to VIN, allowing self-start-up when the applied input voltage exceeds the minimum V_{IN_OPERATE}.

In active mode, depending on the load current, input voltage, and output voltage, the LM6x4xx is in one of six sub-modes:

• Continuous conduction mode (CCM) with fixed switching frequency and peak current mode operation
• Discontinuous conduction mode (DCM) while in auto mode when the load current is lower than half of the inductor current ripple. If current continues to reduce, the device enters Pulse Frequency Modulation (PFM), which reduces the switch frequency to maintain regulation while reducing switching losses to achieve higher efficiency at light load.
• Minimum on-time operation while the on time of the device needed for full-frequency operation at the requested low-duty cycle is not supported by T_{ON_MIN}
• Forced pulse width modulation (FPWM) similar to CCM with fixed-switching frequency, but extends the fixed frequency range of operation from full to no load
• Dropout mode when switching frequency is reduced to minimize dropout
• Recovery from dropout similar to other modes of operation except the output voltage setpoint is gradually moved up until the programmed setpoint is reached.