®
RT2657
2.25MHz 600mA Synchronous Step-Down Converter
General Description
The RT2657 is a high efficiency Pulse-Width-Modulated
(PWM) step-down DC/DC converter, capable of delivering
600mA output current over a wide input voltage range from
2.7V to 5.5V. The RT2657 is ideally suited for portable
electronic devices that are powered from 1-cell Li-ion
battery or from other power sources such as cellular
phones, PDAs, hand-held devices, game console and
related accessories.
The internal synchronous rectifier with low R
DS(ON)
dramatically reduces conduction loss at PWM mode.
No external Schottky diode is required in practical
applications. The RT2657 enters Low Dropout Mode when
normal Pulse -Width Mode cannot provide regulated output
voltage by continuously turning on the upper P-MOSFET.
The RT2657 enters shut-down mode and consumes less
than 5μA when the EN pin is pulled low. The switching
ripple is easily smoothed-out by small package filtering
elements due to a fixed operating frequency of 2.25MHz.
The RT2657 is available in the small WDFN-6SL 2x2
package.
Features
V
IN
Range 2.7V to 5.5V
V
OUT
Range 0.6V to 5.5V (100% Duty Ratio Operation)
V
REF
= 0.6V
I
SD
≤
5μA (V
EN
= 0V)
μ
Current Mode Control, Internal Compensation
Fixed F
SW
2.25MHz
R
DS(ON)
230mΩ HS/250mΩ LS (P-MOSFET/
Ω
Ω
N-MOSFET)
Enable (V
IH
= 1V, V
IL
= 0.4V); Int. Soft-Start (0.3ms)
Up to 600mA Output Current
Up to 90% Efficiency
Peak I
LIMIT
(1.5A Typical / 0.8A Min); UVLO; UVP;
V
IN
and V
OUT
OVP; and OTP (150°C)
°
No Schottky Diode Required
Internal Compensation to Reduce External
Components
RoHS Compliant and Halogen Free
Applications
Marking Information
1W : Product Code
1WW
W : Date Code
Portable Instruments
Game Console and Accessories
Microprocessors and DSP Core Supplies
Cellular Phones
Wireless and DSL Modems
PC Cards
Automotive InfoTainMent
Simplified Application Circuit
RT2657
V
IN
C
IN
EN
GND
FB
R2
VIN
LX
C1
R1
L1
V
OUT
C
OUT
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS2657-00
November 2013
www.richtek.com
1
RT2657
Ordering Information
RT2657
(2)
Taping Type ( Pin1 at Q2)
Package Type
QW : WDFN-6SL 2x2 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Note :
Richtek products are :
½
Pin Configurations
(TOP VIEW)
GND
LX
NC
FB
1
2
3
6
5
4
GND
VIN
EN
7
WDFN-6SL 2x2
RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
½
Function Pin Description
Pin No.
1
2
3
4
5
Pin Name
LX
NC
FB
EN
VIN
Pin Function
Switch Node. Connect to the external inductor.
No Internal Connection. Connect to GND.
Feedback Voltage Input. Connect to the external resistor divider.
Enable Control Input (Active High).
Power Input. Connect to the input capacitor.
Power GND. The Exposed Pad must be soldered to a large PCB and connected
to GND for maximum power dissipation.
6,
GND
7 (Exposed Pad)
Function Block Diagram
EN
VIN
OSC &
Shutdown
Control
Slope
Compensation
Current
Sense
Error
Amplifier
PWM
Comparator
R
S1
Current
Limit
Detector
FB
Control
Logic
Driver
LX
R
C
COMP
R
S2
UVLO &
Power Good
Detector
GND
V
REF
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS2657-00
November 2013
RT2657
Operation
The RT2657 is a synchronous low voltage Buck Converter
that can support the input voltage range from 2.7V to 5.5V
and the output current can be up to 0.6A. The RT2657
uses a constant frequency, current mode architecture. In
normal operation, the high-side P-MOSFET is turned on
when the Switch Controller is set by the oscillator (OSC)
and is turned off when the current comparator resets the
Switch Controller.
The high-side MOSFET peak current is measured by
internal R
SENSE
. The current signal is where Slope
Compensator works together with sensing voltage of
R
SENSE
. The error amplifier EA adjusts COMP voltage by
comparing the feedback signal (V
FB
) from the output
voltage with the internal 0.6V reference. When the load
current increases, it causes a drop in the feedback voltage
relative to the reference. The COMP voltage then rises to
allow higher inductor current to match the load current.
Enable Comparator
The EN pin can be connected to VIN through a 100kΩ
resistor for automatic startup.
Soft-Start (SS)
An internal current source (25nA) charges an internal
capacitor (15pF) to build the soft-start ramp voltage (V
SS
).
The V
FB
voltage will track the internal ramp voltage during
soft-start interval. The typical soft-start time is 300μs.
UV Comparator
If the feedback voltage (V
FB
) is lower than threshold voltage
0.2V, the UV Comparator's output will go high and the
Switch Controller will turn off the high-side MOSFET.
Oscillator (OSC)
The internal oscillator runs at 2.25MHz.
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS2657-00
November 2013
www.richtek.com
3
RT2657
Absolute Maximum Ratings
(Note 1)
−0.3V
to 6.5V
−0.3V
to (V
IN
+ 0.3V)
−0.3V
to 6V
0.833W
120°C/W
Supply Input Voltage, V
IN
-----------------------------------------------------------------------------------------
Switch Voltage, LX -------------------------------------------------------------------------------------------------
All Other Pins -------------------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
WDFN-6SL 2x2 -----------------------------------------------------------------------------------------------------
Package Thermal Resistance (Note 2)
WDFN-6SL 2x2,
θ
JA
------------------------------------------------------------------------------------------------
WDFN-6SL 2x2,
θ
JC
----------------------------------------------------------------------------------------------- 12°C/W
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------ 260°C
Junction Temperature ---------------------------------------------------------------------------------------------- 150°C
Storage Temperature Range -------------------------------------------------------------------------------------
−65°C
to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Model) --------------------------------------------------------------------------------------- 2kV
(Note 4)
Recommended Operating Conditions
Supply Input Voltage, V
IN
----------------------------------------------------------------------------------------- 2.7V to 5.5V
Junction Temperature Range -------------------------------------------------------------------------------------
−40°C
to 125°C
Ambient Temperature Range -------------------------------------------------------------------------------------
−40°C
to 85°C
Electrical Characteristics
(V
IN
= 3.6V, T
A
=
−40°C
to 85°C unless otherwise specified)
Parameter
Output Current
Quiescent Current
Feedback Voltage
Symbol
I
OUT
I
Q
V
FB
Test Conditions
V
IN
= 2.7V to 5.5V
V
EN
= 1V, V
FB
= 0.5V
V
IN
= 2.7V to 5.5V @ T
A
= 25C
V
IN
= 2.7V to 5.5V
V
IN
Rising
Hysteresis
V
EN
= 0V
Min
--
--
588
585
1.85
--
--
--
Typ
--
300
600
600
2.2
0.2
--
2.25
--
--
150
230
250
1.5
1
Max
0.6
--
612
615
2.55
--
5
--
V
IN
0.4
--
--
--
--
--
Unit
A
A
mV
V
V
A
MHz
V
V
°C
m
m
A
%
Under-Voltage Lockout Threshold V
UVLO
Shutdown Current
Switching Frequency
EN Input Voltage
Logic-High
Logic-Low
Thermal Shutdown Temperature
Switch
On-Resistance
Peak Current Limit
Output Voltage Load Regulation
High-Side
Low-Side
V
IH
V
IL
T
SD
I
SHDN
1
--
--
--
--
0.8
0mA < I
OUT
< 0.6A
--
R
DS(ON)_H
I
SW
= 0.2A
R
DS(ON)_L
I
SW
= 0.2A
I
LIM
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS2657-00
November 2013
RT2657
Note 1.
Stresses beyond those listed
“Absolute
Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in
the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may
affect device reliability.
Note 2.
θ
JA
is measured at T
A
= 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7.
Note 3.
Devices are ESD sensitive. Handling precaution is recommended.
Note 4.
The device is not guaranteed to function outside its operating conditions.
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS2657-00
November 2013
www.richtek.com
5
嵌入式系统
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
