LM2747_15 Datasheet, PDF (1/38 Pages) Texas Instruments – Synchronous Buck Controller with Pre-Bias Startup, and Optional Clock Synchronization

LM2747
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SNVS370B – MARCH 2006 – REVISED MARCH 2013
LM2747 Synchronous Buck Controller with Pre-Bias Startup, and Optional Clock
Synchronization
Check for Samples: LM2747
FEATURES
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•2 ±1% Feedback Voltage Accuracy Over
Temperature
• Switching Frequency from 50 kHz to 1 MHz
• Switching Frequency Synchronize Range 250
kHz to 1 MHz
• Startup with a Pre-Biased Output Load
• Power Stage Input Voltage from 1V to 14V
• Control Stage Input Voltage from 3V to 6V
• Output Voltage Adjustable Down to 0.6V
• Power Good Flag and Shutdown
• Output Overvoltage and Undervoltage
Detection
• Low-Side Adjustable Current Sensing
• Adjustable Soft-Start
• Tracking and Sequencing with Shutdown and
Soft Start Pins
• 14-Pin TSSOP Package
APPLICATIONS
• Down Conversion from 3.3V
• Cable Modem, DSL and ADSL
• Laser Jet and Ink Jet Printers
• Low Voltage Power Modules
• DSP, ASIC, Core and I/O
DESCRIPTION
The LM2747 is a high-speed synchronous buck
regulator controller with a feedback voltage accuracy
of ±1%. It can provide simple down conversion to
output voltages as low as 0.6V. Though the control
section of the IC is rated for 3 to 6V, the driver
section is designed to accept input supply rails as
high as 14V. The use of adaptive non-overlapping
MOSFET gate drivers helps avoid potential shoot-
through problems while maintaining high efficiency.
The IC is designed for the more cost-effective option
of driving only N-channel MOSFETs in both the high-
side and low-side positions. It senses the low-side
switch voltage drop for providing a simple, adjustable
current limit.
The LM2747 features a fixed-frequency voltage-mode
PWM control architecture which is adjustable from 50
kHz to 1 MHz with one external resistor. In addition,
the LM2747 also allows the switching frequency to be
synchronized to an external clock signal over the
range of 250 kHz to 1 MHz. This wide range of
switching frequency gives the power supply designer
the flexibility to make better tradeoffs between
component size, cost and efficiency.
Features include the ability to startup with a pre-
biased load on the output, soft-start, input
undervoltage lockout (UVLO) and Power Good
(based on both undervoltage and overvoltage
detection). In addition, the shutdown pin of the IC can
be used for providing startup delay, and the soft-start
pin can be used for implementing precise tracking, for
the purpose of sequencing with respect to an external
rail.
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2
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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