®
RT8070
4A, 2MHz, Synchronous Step-Down Converter
General Description
The RT8070 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 4A 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
RT8070
Package Type
SP : SOP-8 (Exposed Pad-Option 1)
QW : WDFN-8L 3x3 (W-Type)
Lead Plating System
Z : ECO (Ecological Element with
Halogen Free and Pb free)
Note :
Richtek products are :
½
Marking Information
RT8070ZSP
RT8070ZSP : Product Number
RT8070
ZSPYMDNN
YMDNN : Date Code
RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
RT8070ZQW
25 : Product Code
Suitable for use in SnPb or Pb-free soldering processes.
½
25 YM
DNN
YMDNN : Date Code
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8070-08 February 2015
www.richtek.com
1
RT8070
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
RT8070
4 VIN
LX 5
C
IN
10µF
8 PGOOD
6 RT
FB 7
COMP
1
R
COMP
C
COMP
Chip Enable
3 EN
GND 9 (Exposed Pad)
SS 2
C
SS
10nF
R2
L
V
OUT
R1
C
OUT
Table 1. Recommended Components Selection for f
SW
= 1MHz
V
OUT
(V)
3.3
2.5
1.8
1.5
1.2
1
R1 (k)
75
51
30
21
12
6
R2 (k)
24
24
24
24
24
24
R
COMP
(k)
33
22
15
13
11
8.2
C
COMP
(pF)
560
560
560
560
560
560
GND
L (H)
2
2
1.5
1.5
1.5
1.5
C
OUT
(F)
22
22
22
22
22
22
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS8070-08 February 2015
RT8070
Functional Pin Description
Pin No.
SOP-8
(Exposed Pad)
1
WDFN-8L 3x3
1
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 800s (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.
COMP
2
3
4
5
6
2
3
4
5
6
SS
EN
VIN
LX
RT
7
8
9
(Exposed Pad)
7
8
9
(Exposed Pad)
FB
PGOOD
GND
Function Block Diagram
SD
RT
ISEN
OSC
Slope
Com
VIN
COMP
0.8V
FB
EA
Output
Clamp
OC
Limit
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
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8070-08 February 2015
www.richtek.com
3
RT8070
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
Current Sense
Trans-resistance
Symbol
V
REF
Test Conditions
Min
0.784
Typ
0.8
460
--
0.1
0.25
400
0.3
Max
0.816
--
10
--
--
--
--
Unit
V
A
%/V
%
A/V
Active, V
FB
= 0.78V, Not Switching
Shutdown
V
IN
= 2.7V to 5.5V
0A < I
LOAD
< 4A
gm
R
T
--
--
--
--
--
--
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS8070-08 February 2015
RT8070
Parameter
Switching Frequency
EN Input
Voltage
Logic-High
Logic-Low
V
IH
V
IL
R
DS(ON)_N
I
LX
= 0.5A
I
LIM
V
IN
Rising
V
IN
Falling
V
RT
t
SS
V
RT
Rising
C
SS
= 10nF
Symbol
Test Conditions
R
OSC
= 300k
Switching
Min
0.8
0.2
1.6
--
--
--
4.7
--
--
--
--
--
Typ
1
--
--
--
110
70
5.8
2.4
2.2
Max
1.2
2
--
0.4
180
120
--
--
--
Unit
MHz
V
m
m
A
V
V
s
%V
OUT
Switch On-Resistance, High R
DS(ON)_P
I
LX
= 0.5A
Switch On-Resistance, Low
Peak Current Limit
Under Voltage Lockout
Threshold
RT Shutdown Threshold
Soft-Start Period
PGOOD Trip Threshold
V
IN
0.7 V
IN
0.4
800
87.5
--
--
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
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8070-08 February 2015
www.richtek.com
5
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