®
RT8065
3A, 2MHz, Synchronous Step-Down Converter
General Description
The RT8065 is a high efficiency synchronous, step-down
DC/DC converter. Its input voltage range is from 2.7V to
5.5V and provides an adjustable regulated output voltage
from 0.8V to 5V while delivering up to 3A of output current.
The internal synchronous low on-resistance power
switches increase efficiency and eliminate the need for
an external Schottky diode. The default switching
frequency is set at 2MHz, if the RT pin is left open. It can
also be varied from 200kHz to 2MHz by adding an external
resistor. Current mode operation with external
compensation allows the transient response to be
optimized over a wide range of loads and output capacitors.
Features
High Efficiency : Up to 95%
Adjustable Frequency : 200kHz to 2MHz
No Schottky Diode Required
0.8V Reference Allows Low Output Voltage
Low Dropout Operation : 100% Duty Cycle
Enable Function
External Soft-Start
Power Good Function
RoHS Compliant and Halogen Free
Applications
LCD TV and Monitor
Notebook Computers
Distributed Power Systems
IP Phones
Digital Cameras
Ordering Information
RT8065
Package Type
SP : SOP-8 (Exposed Pad-Option 2)
QW : WDFN-8L 3x3 (W-Type)
Lead Plating System
Z : ECO (Ecological Element with
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
RT8065ZSP
RT8065ZSP : Product Number
RT8065
ZSPYMDNN
YMDNN : Date Code
RT8065ZQW
29 : Product Code
29 YM
DNN
YMDNN : Date Code
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8065-07
November 2012
www.richtek.com
1
RT8065
Pin Configurations
(TOP VIEW)
COMP
SS
EN
VIN
2
3
4
8
PGOOD
FB
RT
LX
GND
9
7
6
5
COMP
SS
EN
VIN
1
2
3
4
8
7
6
5
9
PGOOD
FB
RT
LX
SOP-8 (Exposed Pad)
WDFN-8L 3x3
Typical Application Circuit
V
IN
2.7V to 5.5V
R3
100k
PGOOD
R
OSC
4
C
IN
10µF
8 PGOOD
6 RT
3
FB
COMP
7
1
R
COMP
C
COMP
GND 9 (Exposed Pad)
SS 2
C
SS
10nF
R2
RT8065
5
LX
VIN
L
V
OUT
R1
C
OUT
Chip Enable
EN
Table 1. Recommended Components Selection for f
SW
= 1MHz
V
OUT
(V)
3.3
2.5
1.8
1.5
1.2
1
R1 (kΩ)
75
51
30
21
12
6
R2 (kΩ)
24
24
24
24
24
24
R
COMP
(kΩ)
33
22
15
13
11
8.2
C
COMP
(pF)
560
560
560
560
560
560
L (μH)
2
2
1.5
1.5
1.5
1.5
C
OUT
(μF)
22
22
22
22
22
22
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
GND
DS8065-07
November 2012
RT8065
Functional Pin Description
Pin No.
SOP-8
(Exposed Pad)
1
WDFN-8L 3x3
Pin Name
Pin Function
Error Amplifier Compensation Point. The current comparator
threshold increases with this control voltage. Connect
external compensation elements to this pin to stabilize the
control loop.
Soft-Start Control Input. Connect a capacitor from SS to GND
to set the soft-start period. A 10nF capacitor sets the
soft-start period to 800μs (typ.).
Enable Control Input. Float or connect this pin to logic high
for enable. Connect to GND for disable.
Power Input Supply. Decouple this pin to GND with a
capacitor.
Internal Power MOSFET Switches Output. Connect this pin
to the inductor.
Oscillator Resistor Input. Connect a resistor from this pin to
GND sets the switching frequency. If this pin is floating, the
frequency will be set at 2MHz internally.
Feedback. Receives the feedback voltage from a resistive
divider connected across the output.
Power Good Indicator. This pin is an open drain logic output
that is pulled to ground when the output voltage is not within
±12.5%
of regulation point.
Ground. The exposed pad must be soldered to a large PCB
and connected to GND for maximum power dissipation.
1
COMP
2
3
4
5
6
2
3
4
5
6
SS
EN
VIN
LX
RT
7
7
FB
8
8
PGOOD
9 (Exposed Pad) 9 (Exposed Pad) GND
Function Block Diagram
SD
RT
ISEN
OSC
Slope
Com
OC
Limit
VIN
COMP
0.8V
FB
EA
Output
Clamp
10µA
SS
Hiccup
Control
Logic
0.7V
EN
Enable
P-G
UV
OTP
Driver
LX
NISEN
N-MOSFET I
LIM
GND
0.4V
PGOOD
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8065-07
November 2012
www.richtek.com
3
RT8065
Absolute Maximum Ratings
(Note 1)
−0.3V
to 6V
−0.3V
to (V
IN
+ 0.3V)
−5V
to 8.5V
−0.3V
to (V
IN
+ 0.3V)
5A
1.333W
Supply Input Voltage, VIN -----------------------------------------------------------------------------------------
LX Pin Switch Voltage ----------------------------------------------------------------------------------------------
<10ns ------------------------------------------------------------------------------------------------------------------
Other I/O Pin Voltages ---------------------------------------------------------------------------------------------
LX Pin Switch Current ----------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
SOP-8 (Exposed Pad) --------------------------------------------------------------------------------------------
WDFN-8L 3x3 -------------------------------------------------------------------------------------------------------- 1.429W
Package Thermal Resistance (Note 2)
SOP-8 (Exposed Pad),
θ
JA
---------------------------------------------------------------------------------------- 75°C/W
SOP-8 (Exposed Pad),
θ
JC
--------------------------------------------------------------------------------------- 15°C/W
WDFN-8L 3x3,
θ
JA
--------------------------------------------------------------------------------------------------- 70°C/W
WDFN-8L 3x3,
θ
JC
--------------------------------------------------------------------------------------------------- 8.2°C/W
Junction Temperature ----------------------------------------------------------------------------------------------- 150°C
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------- 260°C
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, VIN ----------------------------------------------------------------------------------------- 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
= 3.3V, T
A
= 25°C, unless otherwise specified)
Parameter
Feedback Reference Voltage
DC Bias Current
Output Voltage Line Regulation
Output Voltage Load Regulation
Error Amplifier
Trans-conductance
Symbol
V
REF
Test Conditions
Min
0.784
Typ
0.8
460
--
0.1
0.25
400
0.3
1
--
--
--
Max
0.816
--
10
--
--
--
--
1.2
2
--
0.4
Unit
V
μA
%/V
%
μA/V
Ω
MHz
Active , V
FB
= 0.78V, Not Switching
Shutdown
V
IN
= 2.7V to 5.5V
0A < I
LOAD
< 3A
gm
--
--
--
--
--
--
Current Sense Trans-resistance R
T
Switching Frequency
Logic-High
Logic-Low
V
IH
V
IL
R
OSC
= 330kΩ
Switching
0.8
0.2
1.6
--
EN Input Voltage
V
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS8065-07
November 2012
RT8065
Parameter
Switch On-Resistance, High
Switch On-Resistance, Low
Peak Current Limit
Under Voltage Lockout
Threshold
RT Shutdown Threshold
Soft-Start Period
PGOOD Trip Threshold
V
RT
t
SS
Symbol
R
DS(ON)_P
R
DS(ON)_N
I
LIM
V
IN
Rising
V
IN
Falling
V
RT
Rising
C
SS
= 10nF
Test Conditions
I
LX
= 0.5A
I
LX
= 0.5A
Min
--
--
3.6
--
--
--
--
--
Typ
120
80
4.5
2.4
2.2
800
87.5
Max
180
120
--
--
--
--
--
Unit
mΩ
mΩ
A
V
V
μs
%V
OUT
V
IN
−
0.7 V
IN
−
0.4
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.
θ
JC
is
measured at the exposed pad of the package.
Note 3.
Devices are ESD sensitive. Handling precaution is recommended.
Note 4.
The device is not guaranteed to function outside its operating conditions.
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8065-07
November 2012
www.richtek.com
5
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