®
RT7277
3A, 18V, 700kHz ACOT
TM
Synchronous Step-Down Converter
General Description
The RT7277 is a synchronous step-down DC/DC converter
with Advanced Constant On-Time (ACOT
TM
) mode control.
It achieves high power density to deliver up to 3A output
current from a 4.5V to 18V input supply. The proprietary
ACOT
TM
mode offers an optimal transient response over a
wide range of loads and all kinds of ceramic capacitors,
which allows the device to adopt very low ESR output
capacitors for ensuring performance stabilization. In
addition, RT7277 keeps an excellent constant switching
frequency under line and load variation and the integrated
synchronous power switches with the ACOT
TM
mode
operation provides high efficiency in whole output current
load range. Cycle-by-cycle current limit provides an
accurate protection by a valley detection of low side
MOSFET and external soft-start setting eliminates input
current surge during startup. Protection functions also
include output under voltage protection, output over voltage
protection, and thermal shutdown.
Features
ACOT
TM
Mode Enables Fast Transient Response
4.5V to 18V Input Voltage Range
3A Output Current
60mΩ Internal Low Site N-MOSFET
Ω
Advanced Constant On-Time Control
Support All Ceramic Capacitors
Up to 95% Efficiency
700kHz Switching Frequency
Adjustable Output Voltage from 0.765V to 8V
Adjustable Soft-Start
Cycle-by-Cycle Current Limit
Input Under Voltage Lockout
Thermal Shutdown
RoHS Compliant and Halogen Free
Applications
Industrial and Commercial Low Power Systems
Computer Peripherals
LCD Monitors and TVs
Green Electronics/Appliances
Point of Load Regulation for High-Performance DSPs,
FPGAs, and ASICs
Marking Information
RT7277GSP : Product Number
RT7277
GSPYMDNN
YMDNN : Date Code
Simplified Application Circuit
V
IN
C1
Chip Enable
C2
RT7277
VIN
SW
BOOT
EN
SS
C5
GND
FB
PVCC
L1
V
OUT
C6
C3
R1
C7
V
PVCC
C4
R2
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7277-00
October 2012
www.richtek.com
1
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
