®
RT8077
2A, 2MHz, Synchronous Step-Down Converter
General Description
The RT8077 is a high efficiency synchronous, step-down
DC/DC converter. Its input voltage range is from 2.6V to
5.5V and provides an adjustable regulated output voltage
from 0.8V to 5V, while delivering up to 2A of output current.
The internal synchronous low on-resistance power
switches increase efficiency and eliminate the need for
an external Schottky diode. The switching frequency is
set by an external resistor or can be synchronized to an
external clock. The 100% duty cycle provides low dropout
operation extending battery life in portable systems.
Current mode operation with external compensation
allows the transient response to be optimized over a wide
range of loads and output capacitors.
The 100% duty cycle in Low Dropout Operation further
maximize battery life.
The RT8077 is available in the WDFN-8L 2x2 package.
Features
High Efficiency : Up to 95%
Low R
DS(ON)
Internal Switches : 90mΩ
Ω
Programmable Frequency : 300kHz to 2MHz
No Schottky Diode Required
0.8V Reference Allows for Low Output Voltage
Low Dropout Operation : 100% Duty Cycle
2.6V to 5.5V Input Voltage Range
V
OUT
Range from 0.8V to 5V
Up to 2A Output Current
Thermal Shutdown
RoHS Compliant and Halogen Free
Applications
Portable Instruments
Battery-Powered Equipment
Notebook Computers
Distributed Power Systems
IP Phones
Digital Cameras
Dynamic Supply Bias for GSM/EDGE PAs and 3G/4G
PAs
Simplified Application Circuit
V
IN
PVDD
COMP
RT8077
FB
RT
PGND
LX
GND
EN
EN
C
OUT
L1
V
OUT
R
COMP
C
COMP
R2
C
F
R1
C
IN
R
OSC
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8077-01
September 2013
www.richtek.com
1
RT8077
Ordering Information
RT8077
Package Type
QW : WDFN-8L 2x2 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Note :
Richtek products are :
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.
Marking Information
0B : Product Code
0BW
W : Date Code
Pin Configurations
(TOP VIEW)
RT
GND
LX
PGND
1
2
3
4
8
7
6
5
9
COMP
FB
EN
PVDD
WDFN-8L 2x2
Functional Pin Description
Pin No.
1
Pin Name
RT
Pin Function
Switching Frequency Setting. Connecting a resistor to ground from this pin sets
the switching frequency.
Signal Ground. All small-signal components and compensation components
should be connected to this ground, which in turn connects to PGND at one point.
Switch Node. Connect this pin to the inductor.
Power Ground. Connect this pin close to the negative terminal of C
IN
and C
OUT
.
Power Input. Decouple this pin to PGND with a capacitor.
Enable Control Input. A logic-high (1.2V < EN < 5.5V) enables the converter;
logic-low forces the IC into shutdown mode.
Feedback Voltage Input. This pin receives the feedback voltage from a resistive
divider connected across the output.
Compensation Node. The current comparator threshold increases with this control
voltage. Connect external compensation elements to this pin to stabilize the
control loop.
2,
GND
9 (Exposed Pad)
3
4
5
6
7
LX
PGND
PVDD
EN
FB
8
COMP
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS8077-01
GND
September 2013
RT8077
Function Block Diagram
EN
RT
SD
OSC
COMP
V
REF
FB
EA
Output
Clamp
Slope
Comp.
ISEN
PVDD
OC
Limit
Internal
Soft- Start
Controller
Logic
0.2V
Driver
LX
NISEN
POR
PVDD
OTP
N-MOSFET I
LIM
PGND
GND
Operation
The RT8077 is a synchronous low voltage Buck converter
that can support the input voltage range from 2.6V to 5.5V
and the output current can be up to 2A. The RT8077 uses
a constant frequency, current mode architecture. In normal
operation, the high-side P-MOSFET is turned on when
the logic controller is set by the oscillator (OSC) and is
turned off when the current comparator resets the logic
controller.
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 0.8V 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. 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 the programmable frequency
range : 300kHz to 2MHz
Enable Comparator
The EN pin can be connected to VIN through a 100kΩ
external resistor for automatic startup.
Soft-Start (SS)
An internal current source charges an internal capacitor
to build the soft-start ramp voltage. The V
FB
voltage will
track the internal ramp voltage during soft-start interval.
The typical soft-start time is 1ms.
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8077-01
September 2013
www.richtek.com
3
RT8077
Absolute Maximum Ratings
(Note 1)
−0.3V
to 6.5V
0.833W
120°C/W
150°C
260°C
Supply Input Voltage, PVDD ---------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
WDFN-8L 2x2 ---------------------------------------------------------------------------------------------------------------
Package Thermal Resistance (Note 2)
WDFN-8L 2x2,
θ
JA
----------------------------------------------------------------------------------------------------------
Junction Temperature ------------------------------------------------------------------------------------------------------
Lead Temperature (Soldering, 10 sec.) --------------------------------------------------------------------------------
Storage Temperature Range ---------------------------------------------------------------------------------------------
−65°C
to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Model) ----------------------------------------------------------------------------------------------- 2kV
Recommended Operating Conditions
(Note 4)
Supply Input Voltage, PVDD --------------------------------------------------------------------------------------------- 2.6V to 5.5V
Junction Temperature Range ---------------------------------------------------------------------------------------------
−40°C
to 125°C
Ambient Temperature Range ---------------------------------------------------------------------------------------------
−40°C
to 85°C
Electrical Characteristics
(V
IN
= 3.3V, T
A
= 25°C, unless otherwise specified)
Parameter
Feedback Reference Voltage
EN Input Voltage
Logic-High
Logic-Low
Symbol
V
REF
V
EN_H
V
EN_L
I
FB
Test Conditions
Min
0.788
1.2
--
Typ
0.8
--
--
0.1
270
--
0.1
0.4
400
0.2
1.8
--
90
90
--
2.4
2.2
150
20
Max
0.812
5.5
0.4
0.4
--
1
--
--
--
--
2.16
2
130
130
--
--
--
--
--
Unit
V
V
μA
μA
%/V
%
μA/V
Ω
MHz
Feedback Leakage Current
Quiescent Current
Output Voltage Line Regulation
Output Voltage Load Regulation
V
FB
= 3.3V
V
FB
= 0.85V
Shutdown, V
EN
= 0V
V
IN
= 2.6V to 5.5V
V
IN
= 5V, V
OUT
= 3.3V,
I
OUT
= 0A to 2A
--
--
--
--
--
--
--
ΔV
LINE
ΔV
LOAD
Error Amplifier Transconductance gm
Current Sense Transresistance
Switching Frequency
Switch
On-Resistance
High-Side
Low-Side
R
S
R
OSC
= 180kΩ
Adjustable Switching
Frequency Range
R
DS(ON)_P
I
SW
= 0.3A, PVDD = 3.6V
R
DS(ON)_N
I
SW
= 0.3A, PVDD = 3.6V
I
LIM
V
DD
Rising
V
DD
Falling
T
SD
ΔT
SD
Rising
1.44
0.3
--
--
3
--
--
--
--
mΩ
A
V
Peak Current Limit
Under-Voltage Lockout Threshold
(Note 5)
Over Temperature Protection
Thermal Shutdown
Thermal Shutdown Hysteresis
°C
°C
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS8077-01
September 2013
RT8077
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.
Note 5.
Guaranteed by design.
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8077-01
September 2013
www.richtek.com
5
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