1FEATURES

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 pre•

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 highside

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.