The LMR544xx is in active mode when both
VEN and VIN are above their respective operating
threshold. The simplest way to enable the LMR544xx is to connect the EN pin to VIN
pin. This allows self-start-up when the input voltage is in the operating range of
4.0 V to 36 V. See Section 7.3.3 for details on setting these operating levels.
In active mode, depending on the load current, the
LMR544xx is in one of four modes:
- Continuous conduction mode (CCM)
with fixed switching frequency when load current is greater than half of the
peak-to-peak inductor current ripple (for both PFM and FPWM
versions)
- Discontinuous conduction mode
(DCM) with fixed switching frequency when load current is less than half of the
peak-to-peak inductor current ripple(only for PFM version)
- Pulse frequency modulation mode
(PFM) when switching frequency is decreased at very light load (only for PFM
version)
- Forced pulse width modulation mode (FPWM) with
fixed switching frequency even at light load (only for FPWM version)