RT7275 Datasheet, PDF (1/24 Pages) Richtek Technology Corporation – 3A, 18V, 700kHz ACOTTM Synchronous Step-Down Converter

®
RT7275/76
3A, 18V, 700kHz ACOT^TM Synchronous Step-Down Converter
General Description
The RT7275/76 are high-performance 700kHz 3A step-
down regulators with internal power switches and
synchronous rectifiers. They feature quick transient
response using their Advanced Constant On-Time
(ACOT^TM) control architecture that provides stable
operation with small ceramic output capacitors and without
complicated external compensation, among other benefits.
The input voltage range is from 4.5V to 18V and the output
is adjustable from 0.765V to 8V.
The proprietary ACOT^TM control improves upon other fast-
response constant on-time architectures, achieving nearly
constant switching frequency over line, load, and output
voltage ranges. Since there is no internal clock, response
to transients is nearly instantaneous and inductor current
can ramp quickly to maintain output regulation without
large bulk output capacitance. The RT7275/76 are stable
with and optimized for ceramic output capacitors.
With internal 90mΩ switches and 60mΩ synchronous
rectifiers, the RT7275/76 display excellent efficiency and
good behavior across a range of applications, especially
for low output voltages and low duty cycles. Cycle-by-
cycle current limit, input under-voltage lock-out,
externally-adjustable soft-start, output under- and over-
voltage protection, and thermal shutdown provide safe and
smooth operation in all operating conditions.
The RT7275 and RT7276 are each available in WDFN-10L
3x3 and PTSSOP-14 packages, with exposed thermal
pads.
Simplified Application Circuit
V_IN
Input Signal
Power Good
RT7275/76
VIN
SW
VINR
EN
BOOT
FB
PGOOD
PVCC
VOUT
SS
PGND GND
V_OUT
Features
z Fast Transient Response
z Steady 700kHz Switching Frequency
` At all Load Currents (RT7275)
` Discontinuous Operating Mode at Light Load
(RT7276)
z 3A Output Current
z Advanced Constant On-Time (ACOT^TM) Control
z Optimized for Ceramic Output Capacitors
z 4.5V to 18V Input Voltage Range
z Internal 90mΩ Switch and 60mΩ Synchronous
Rectifier
z 0.765V to 8V Adjustable Output Voltage
z Externally-adjustable, Pre-biased Compatible Soft-
Start
z Cycle-by-Cycle Current Limit
z Optional Output Discharge Function (PTSSOP-14
Only)
z Output Over- and Under-voltage Shut-down
Applications
z Industrial and Commercial Low Power Systems
z Computer Peripherals
z LCD Monitors and TVs
z Green Electronics/Appliances
z Point of Load Regulation for High-Performance DSPs,
FPGAs, and ASICs
z Not Recommended for Sink/Source Applications
Fast-Transient Response
RT7275
VOUT
(20mV/Div)
IOUT
(2A/Div)
VOUT = 12V, VOUT = 1.05V, IOUT = 0 to 3A
Time (100μs/Div)
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS7275/76-00 January 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
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