LM3674_15 Datasheet, PDF (11/26 Pages) Texas Instruments – LM3674 2-MHz, 600-mA Step-Down DC-DC Converter in SOT-23

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LM3674
SNVS405G – DECEMBER 2005 – REVISED APRIL 2015
Feature Description (continued)
7.3.2.1 Internal Synchronous Rectification
While in PWM mode, the LM3674 uses an internal NFET as a synchronous rectifier to reduce rectifier forward
voltage drop and associated power loss. Synchronous rectification provides a significant improvement in
efficiency whenever the output voltage is relatively low compared to the voltage drop across an ordinary rectifier
diode.
7.3.2.2 Current Limiting
A current limit feature allows the LM3674 to protect itself and external components during overload conditions.
PWM mode implements current limiting using an internal comparator that trips at 1020 mA (typical). If the output
is shorted to ground, then the device enters a timed current-limit mode where the NFET is turned on for a longer
duration until the inductor current falls below a low threshold, ensuring inductor current has more time to decay,
and thereby preventing runaway.
7.4 Device Functional Modes
There are two modes of operation depending on the current required: Pulse Width Modulation (PWM) and
shutdown. The device operates in PWM mode throughout the I_OUT range. Shutdown mode turns off the device,
offering the lowest current consumption (I_SHUTDOWN = 0.01 µA, typical). Additional features include soft-start,
undervoltage protection, and current overload protection.
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