®
RT7273
3-CH, 18V, Synchronous Step-Down Converter
General Description
The RT7273 features three synchronous wide input range
high efficiency Buck converters. The converters are
designed to simplify its application while giving the designer
the option to optimize their usage according to the target
application.
The converters can operate in 5V, 9V or 12V systems
and have integrated power transistors. The output voltage
can be set externally using a resistor divider to any value
between 0.8V and the input supply minus 1V. Each
converter features an enable pin that allows a delayed
start-up for sequencing purposes, a soft-start pin that
allows adjustable soft-start time by choosing the soft-
start capacitor, and a current limit pin (RLIMx) to adjust
current limit by selecting an external resistor. The COMP
pin allows optimizing transient versus dc accuracy
response with a simple RC compensation.
The switching frequency of the converters can either be
set with an external resistor connected to ROSC pin or
be synchronized to an external clock connected to SYNC
pin if needed. The switching converters are designed to
operate from 300kHz to 2.2MHz. The converters operate
with 180
°
phase between CH 1 and CH 2, CH 3 (CH 2 and
CH 3 ran in phase) to minimize the input filter requirements.
The RT7273 also features a low power mode enabled by
an external signal, which allows for a reduction on the
input power supplied to the system when the host
processor is in stand-by (low activity) mode.
Features
Wide Input Supply Voltage Range : 4.5V to 18V
Output Range : 0.8V to (VIN
−
1V)
Fully Integrated Triple-Buck
�½
Maximum Current 3.5A/2.5A/2.5A
�½
Continuous Operation 3A/2A/2A
High Efficiency
Switching Frequency
�½
300kHz to 2.2MHz Set by External Resistor
External Synchronization Pin for Oscillator
External Enable/Sequencing Pins
Adjustable Cycle-By-Cycle Current Limit Set by
External Resistor
Soft-Start
Current Mode Control with Simple Compensation
Circuit
Power Good Indicator
Discontinuous Operating Mode at Light Load when
LOWP = High
RoHS Compliant and Halogen Free
Simplified Application Circuit
V
IN
VINx
VINR
RT7273
LX1
FB1
LX2
FB2
LX3
GND
FB3
V
OUT3
V
OUT2
V
OUT1
ENx
SYNC
PGOOD
LOWP
SSx
RLIMx
ROSC
Copyright
©
2014 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7273-04
October 2014
www.richtek.com
1
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
