19

LMR23630

www.ti.com

SNVSAH2C – DECEMBER 2015 – REVISED JUNE 2017

Product Folder Links: LMR23630

Submit Documentation Feedback

Copyright © 2015–2017, Texas Instruments Incorporated

8.4 Device Functional Modes

8.4.1 Shutdown Mode

is below their respective UVLO level, the regulator is turned off.

8.4.2 Active Mode

respective UVLO level. The simplest way to enable the LMR23630 is to connect the EN pin to VIN pin. This

allows self startup when the input voltage is in the operating range 4.5 V (HSOIC) and 4 V (WSON) to 36 V. See

to VCC, UVLO and Enable/Sync for details on setting these operating levels.

In active mode, depending on the load current, the LMR23625 is in one of four modes:

1. Continuous conduction mode (CCM) with fixed switching frequency when load current is above half of the

peak-to-peak inductor current ripple (for both PFM and FPWM options).

2. Discontinuous conduction mode (DCM) with fixed switching frequency when load current is lower than half of

the peak-to-peak inductor current ripple in CCM operation (only for PFM option).

3. Pulse frequency modulation mode (PFM) when switching frequency is decreased at very light load (only for

PFM option).

4. Forced pulse width modulation mode (FPWM) with fixed switching frequency even at light load (only for

FPWM option).

8.4.3 CCM Mode

CCM operation is employed in the LMR23630 when the load current is higher than half of the peak-to-peak

inductor current. In CCM operation, the frequency of operation is fixed, output voltage ripple is at a minimum in

this mode, and the maximum output current of 3 A can be supplied by the LMR23630.

8.4.4 Light Load Operation (PFM Version)

For PFM version, when the load current is lower than half of the peak-to-peak inductor current in CCM, the

LMR23630 operates in DCM, also known as diode emulation mode (DEM). In DCM, the LS switch is turned off

reduced in DCM, compared to forced PWM operation at light load.

At even lighter current loads, PFM is activated to maintain high efficiency operation. When either the minimum

switching frequency decreases to maintain regulation. In PFM, switching frequency is decreased by the control

loop when load current reduces to maintain output voltage regulation. Switching loss is further reduced in PFM

operation due to less frequent switching actions. The external clock synchronizing is not valid when the

LMR23630 device enters into PFM mode.

8.4.5 Light Load Operation (FPWM Version)

For FPWM version, LMR23630 is locked in PWM mode at full load range. This operation is maintained, even at

no-load, by allowing the inductor current to reverse its normal direction. This mode trades off reduced light load

efficiency for low output voltage ripple, tight output voltage regulation, and constant switching frequency. In this

FPWM mode the converter synchronizes to any valid clock signal on the EN/SYNC input.