LM3674_15 Datasheet, PDF (9/26 Pages) Texas Instruments – LM3674 2-MHz, 600-mA Step-Down DC-DC Converter in SOT-23

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7 Detailed Description
LM3674
SNVS405G – DECEMBER 2005 – REVISED APRIL 2015
7.1 Overview
The LM3674, a high-efficiency, step-down, DC-DC switching buck converter, delivers a constant voltage from a
single Li-Ion battery and input voltage rails from 2.7 V to 5.5 V to portable devices such as cell phones and
PDAs. Using a voltage mode architecture with synchronous rectification, the LM3674 has the ability to deliver up
to 600 mA depending on the input voltage, output voltage, ambient temperature, and the inductor chosen.
Additional features include soft-start, undervoltage protection, current overload protection, and thermal overload
protection. As shown in Typical Application Circuit, only three external power components, C_IN, C_OUT, and L₁, are
required for implementation.
The part uses an internal reference voltage of 0.5 V. It is recommended to keep the part in shutdown mode until
the input voltage is 2.7 V or higher.
7.2 Functional Block Diagram
EN
V_IN
SW
Undervoltage
Ramp
Soft
Lockout
Generator
Start
Thermal
Shutdown
Bandgap
2 MHz
Oscillator
Current Limit
Comparator
Ref1
Error
Amp
PWM Comparator
+
-
V_REF
0.5V ⁺
-
+ ^Vcomp
- ^1.0V
Frequency
Compensation
Adjustable Version
Fixed Version
FB
Control Logic
Driver
GND
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