LM43602PWPR datasheet(21/51 Pages) TI2

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LM43602

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SNVSA36C – APRIL 2014 – REVISED OCTOBER 2017

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Device Functional Modes (continued)

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;

3. Pulse Frequency Modulation (PFM) when switching frequency is decreased at very light load;

4. Fold-back mode when switching frequency is decreased to maintain output regulation at lower supply voltage

VIN.

7.4.4 CCM Mode

Constant Current Mode (CCM) operation is employed in the LM43602 when the load current is higher than half

of the peak-to-peak inductor current. In CCM peration, the frequency of operation is fixed unless the the

minimum HS switch ON-time (TON_MIN) or OFF-time (TOFF_MIN) is exceeded. Output voltage ripple will be at a

minimum in this mode and the maximum output current of 2 A can be supplied by the LM43602.

7.4.5 Light Load Operation

When the load current is lower than half of the peak-to-peak inductor current in CCM, the LM43602 will operate

in Discontinuous Conduction Mode (DCM), also known as Diode Emulation Mode (DEM). In DCM operation, the

LS FET is turned off when the inductor current drops to 0 A to improve efficiency. Both switching losses and

conduction losses are reduced in DCM, comparing to forced PWM operation at light load.

At even lighter current loads, Pulse Frequency Mode (PFM) is activated to maintain high efficiency operation.

When the HS switch ON-time reduces to TON_MIN or peak inductor current reduces to its minimum IPEAK-MIN, the

switching frequency will reduce to maintain proper regulation. Efficiency is greatly improved by reducing

switching and gate drive losses.

Figure 35. VOUT = 5 V Fs = 500 kHz

Pulse Frequency Mode Operation

7.4.6 Self-Bias Mode

For highest efficiency of operation, it is recommended that the BIAS pin be connected directly to VOUT when VOUT

≥ 3.3 V. In this Self-Bias Mode of operation, the difference between the input and output voltages of the internal

LDO are reduced and therefore the total efficiency of the LM43602 is improved. These efficiency gains are more

evident during light load operation. During this mode of operation, the LM43602 operates with a minimum

quiescent current of 27 µA (typical). Please refer to VCC, UVLO and BIAS for more details.

LM43602PWPR Datasheet(PDF) 21 Page - Texas Instruments

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