®
RT8073
6A, 2MHz, High Efficiency Synchronous Step-Down Converter
General Description
The RT8073 is a high efficiency PWM step-down converter
and capable of delivering 6A output current over a wide
input voltage range from 2.9V to 5.5V.
The RT8073 provides accurate regulation for a variety of
loads with an
±1%
reference voltage at room temperature.
For reducing inductor size, it provides up to 2MHz
switching frequency. The efficiency is maximized through
the integrated 50mΩ for high side, 35mΩ for low side
MOSFETs and 250μA typical supply current.
The RT8073 features over current protection, frequency
fold back function in shorted circuit, hiccup mode under
voltage protection and over temperature protection.
The RT8073 is available in SOP-8 (Exposed Pad) and
WDFN-12L 3x3 packages.
Features
Ω
Ω
Integrated 50mΩ and 35mΩ MOSFETs
6A Output Current
High Efficiency Up to 95%
2.9V to 5.5V Input Range
Adjustable PWM Frequency : 300kHz to 2MHz
0.8V
±
1% Reference Voltage
Adjustable External Soft-Start
Power Good Indicator (WDFN-12L 3x3 only)
Over Current Protection
Under Voltage Protection
Over Temperature Protection
SOP-8 (Exposed Pad) and 12-Lead WDFN Packages
RoHS Compliant and Halogen Free
Applications
Ordering Information
RT8073
Package Type
SP : SOP-8 (Exposed Pad-Option 2)
QW : WDFN-12L 3x3 (W-Type)
(Exposed Pad-Option 1)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Note :
Richtek products are :
½
Low Voltage, High Density Power Systems
Distributed Power Systems
Point-of-Load Conversions
Marking Information
RT8073GSP
RT8073GSP : Product Number
RT8073
GSPYMDNN
YMDNN : Date Code
RT8073GQW
5C= : Product Code
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.
5C=YM
DNN
YMDNN : Date Code
½
Simplified Application Circuit
V
IN
C
IN
EN
COMP
R
C
C
C
R
T
RT
GND
FB
R
FB2
VIN
RT8073
LX
C
OUT
BOOT
C
BOOT
L
V
OUT
R
FB1
Copyright
©
2014 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8073-02 August 2014
www.richtek.com
1
RT8073
Pin Configurations
(TOP VIEW)
COMP
GND
EN
VIN
2
3
4
8
FB
RT
LX
BOOT
PGND
9
7
6
5
COMP
PGOOD
SS
EN
VIN
VIN
1
2
3
4
5
6
13
12
11
10
9
8
7
FB
RT
LX
LX
LX
BOOT
SOP-8 (Exposed Pad)
WDFN-12L 3x3
Functional Pin Description
Pin No.
SOP-8
(Exposed Pad)
1
2
3
4
5
6
7
8
9
WDFN-12L 3x3
1
--
4
5, 6
7
8, 9, 10
11
12
13
(Exposed Pad)
Pin Name
COMP
GND
EN
VIN
BOOT
LX
RT
FB
PGND
Compensation Node.
Analog Ground.
Chip Enable. Externally pulled high to enable and pulled low to
disable this chip, and it is internally pulled up to high when the
pin is floating.
Power Input.
Bootstrap Supply for High Side Gate Driver.
Switch Node.
Frequency Setting.
Feedback Voltage Input.
Power Ground. The exposed pad must be shouldered to a
large PCB and connected to PGND for maximum power
dissipation.
Power Good Indicator with Open Drain Output. It is high
impedance when the output voltage is regulated. It is internally
pulled low when the chip is shutdown, thermal shutdown or
VIN is under UVLO threshold.
Soft-Start Control.
Pin Function
--
2
PGOOD
--
3
SS
Copyright
©
2014 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
PGND
DS8073-02 August 2014
RT8073
Function Block Diagram
For SOP-8 (Exposed Pad) Package
VIN
V
IN
Internal
pull up
current
EN
EN Threshold
GND
RT
Oscillator
Slope
Compensation
PWM
Comparator
Error
Amplifier
PGND
Control
Logic
Driver
LX
Over Temperature
Protection
Shutdown
Control
UVLO
Current
Sense
BOOT
Soft-Start
Voltage
Reference
FB
COMP
For WDFN-12L 3x3 Package
VIN
V
IN
Internal
pull up
current
EN
EN Threshold
RT
Over Temperature
Protection
Shutdown
Control
Oscillator
Control
Logic
PWM
Comparator
Error
Amplifier
PGND
UVLO
Current
Sense
BOOT
V
IN
SS
Soft-
Start
Voltage
Reference
Slope
Compensation
Driver
LX
FB
PGOOD
Power Good
Threshold
COMP
Copyright
©
2014 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8073-02 August 2014
www.richtek.com
3
RT8073
Operation
The RT8073 is a current mode synchronous step-down
DC/DC converter with two integrated power MOSFETs. It
can deliver up to 6A output current from a 2.9V to 5.5V
input supply. The RT8073's current mode architecture
allows the transient response to be optimized over a wide
input voltage and load range. Cycle-by-cycle current limit
provides protection against shorted outputs and soft-start
eliminates input current surge during start-up.
Soft-Start (SS)
Error Amplifier
The error amplifier 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.
Oscillator (OSC)
The frequency of the oscillator is adjustable by an external
resistor connected between the RT pin and GND. The
available switching frequency range is from 300kHz to
2MHz.
An internal current source charges an external capacitor
to build the soft-start ramp voltage (V
SS
). The V
FB
voltage
will track the V
SS
during soft-start interval. The chip will
use internal soft-start if the SS pin is floating. The nominal
internal soft-start time is 800μs.
Over Temperature Protection (OTP)
The RT8073 implements an internal over temperature
protection. When junction temperature is higher than
165°C, it will stop switching operation. Once the junction
temperature decreases below 145°C, the RT8073 will
automatically resume switching.
PGOOD Comparator
When the feedback voltage (V
FB
) rises above 94% or falls
below 106% of reference voltage, the PGOOD open drain
output will be high impedance. The PGOOD open drain
output will be internally pulled low when the feedback
voltage (V
FB
) falls below 90% or rises above 110% of
reference voltage.
Copyright
©
2014 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS8073-02 August 2014
RT8073
Absolute Maximum Ratings
(Note 1)
−0.3V
to 6.5V
−0.3V
to 6V
−0.3V
to (V
IN
+ 0.3V)
2.041W
1.667W
Supply Input Voltage, VIN -----------------------------------------------------------------------------------------
BOOT to LX -----------------------------------------------------------------------------------------------------------
Other Pins -------------------------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
SOP-8 (Exposed Pad) ---------------------------------------------------------------------------------------------
WDFN-12L 3x3 -------------------------------------------------------------------------------------------------------
Package Thermal Resistance (Note 2)
SOP-8 (Exposed Pad),
θ
JA
---------------------------------------------------------------------------------------- 49°C/W
SOP-8 (Exposed Pad),
θ
JC
--------------------------------------------------------------------------------------- 15°C/W
WDFN-12L 3x3,
θ
JA
------------------------------------------------------------------------------------------------- 60°C/W
WDFN-12L 3x3,
θ
JC
------------------------------------------------------------------------------------------------- 7.5°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
Recommended Operating Conditions
(Note 4)
Supply Input Voltage, VIN ----------------------------------------------------------------------------------------- 2.9V to 5.5V
Junction Temperature Range --------------------------------------------------------------------------------------
−40°C
to 125°C
Ambient Temperature Range --------------------------------------------------------------------------------------
−40°C
to 85°C
Electrical Characteristics
(V
IN
= 5V, C
IN
= 10μF, T
A
= 25°C, unless otherwise specified)
Parameter
Input Power Supply
Under Voltage Lockout Threshold
Quiescent Current
Shutdown Current
Voltage Reference
Voltage Reference
Enable
EN Input Voltage
Logic-High
Logic-Low
Symbol
V
UVLO
I
Q
I
SHDN
V
REF
V
IH
V
IL
Test Conditions
V
IN
Rising
Active, V
FB
= 0.9V, Not switching
Min
--
--
--
0.792
1.5
--
300
Typ
2.6
250
2
0.8
--
--
--
1400
300
80
60
Max
2.8
--
5
0.808
5.5
0.4
2000
--
--
--
--
Unit
V
A
A
V
V
Switching Frequency Setting
Switching Frequency
Minimum On-Time
Minimum Off-Time
f
OSC
R
T
= 28.7k
RT pin is floating
--
--
--
--
kHz
ns
ns
Copyright
©
2014 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8073-02 August 2014
www.richtek.com
5
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