The LMR36503E-Q1 is in active mode whenever the EN pin is above VEN-VOUT, VIN is high enough to satisfy VIN_R, and no other fault conditions are present. The simplest way to enable the operation is to connect the EN pin to VIN, which allows self start-up when the applied input voltage exceeds the minimum VIN_R.
In active mode, depending on the load current, input voltage, and output voltage, the LMR36503E-Q1 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: Discontinuous conduction mode (DCM) 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