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RT2853A/B
3A, 18V, 650kHz, ACOT
TM
Synchronous Step-Down Converter
General Description
The RT2853A/B are high-performance 650kHz 3A step-
down regulators with internal power switches and
synchronous rectifiers. They feature quick transient
response using their Advanced Constant On-Time
(ACOT
TM
) control architecture that provides stable
operation with small ceramic output capacitors and without
complicated external compensation, among other benefits.
The input voltage range is from 4.5V to 18V and the output
is adjustable from 0.765V to 7V.
The proprietary ACOT
TM
control improves upon other fast-
response constant on-time architectures, achieving nearly
constant switching frequency over line, load, and output
voltage ranges. Since there is no internal clock, response
to transients is nearly instantaneous and inductor current
can ramp quickly to maintain output regulation without
large bulk output capacitance. The RT2853A/B are stable
with and optimized for ceramic output capacitors.
With internal 110mΩ switches and 30mΩ synchronous
rectifiers, the RT2853A/B display excellent efficiency and
good behavior across a range of applications, especially
for low output voltages and low duty cycles. Cycle-by-
cycle current limit, input under-voltage lock-out, externally-
adjustable soft-start, output under- and over-voltage
protection, and thermal shutdown provide safe and smooth
operation in all operating conditions.
The RT2853A and RT2853B are each available in
WQFN-16L 3x3 package, with exposed thermal pads.
V
OUT
(50mV/Div)
Features
Fast Transient Response
Steady 650kHz Switching Frequency
Enhanced Efficiency at Light Load (RT2853A)
Advanced Constant On-Time (ACOT
TM
) Control
Optimized for Ceramic Output Capacitors
4.5V to 18V Input Voltage Range
Internal 110mΩ Switch and 30mΩ Synchronous
Ω
Ω
Rectifier
0.765V to 7V Adjustable Output Voltage
Externally-adjustable, Pre-biased Compatible Soft-
Start
Cycle-by-Cycle Current Limit
Optional Output Discharge Function
Output Over- and Under-voltage Shut-down
½
Latched (RT2853ALGQW/RT2853BLGQW Only)
½
With Hiccup Mode (RT2853AHGQW/
RT2853BHGQW Only)
Applications
Industrial and Commercial Low Power Systems
Computer Peripherals
LCD Monitors and TVs
Point of Load Regulation for High-Performance DSPs,
FPGAs, and ASICs
Fast-Transient Response
RT2853B
Simplified Application Circuit
RT2853A/B
VIN
SW
VCC
Power Good
VREG5
Input Signal
PGOOD
BOOT
VS
V
IN
V
OUT
FB
EN
SS
VREG5
GND PGND
I
OUT
(1A/Div)
V
IN
= 12V, V
OUT
= 1.05V, I
OUT
= 0 to 3A
Time (100μs/Div)
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS2853A/B-02 October 2016
www.richtek.com
1
RT2853A/B
Ordering Information
RT2853A/B
Package Type
QW : WQFN-16L 3x3 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
H : Hiccup Mode OVP & UVP
L : Latched OVP & UVP
A : Enhanced Light Load Efficiency
B : Continuous Switching Mode
Note :
Richtek products are :
½
Pin Configurations
(TOP VIEW)
VS
VCC
VIN
VIN
16 15 14 13
FB
VREG5
SS
GND
1
2
3
4
5
6
12
GND
17
7
8
11
10
9
BOOT
SW
SW
SW
WQFN-16L 3x3
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
Marking Information
RT2853AHGQW
2K= : Product Code
RT2853BHGQW
2H= : Product Code
YMDNN : Date Code
2K=YM
DNN
2H=YM
DNN
YMDNN : Date Code
RT2853ALGQW
2J= : Product Code
RT2853BLGQW
2G= : Product Code
YMDNN : Date Code
2J=YM
DNN
2G=YM
DNN
YMDNN : Date Code
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
PGOOD
EN
PGND
PGND
DS2853A/B-02 October 2016
RT2853A/B
Absolute Maximum Ratings
(Note 1)
−0.3V
to 21V
−0.8V
to (V
VIN
+ 0.3V)
−5V
to 25V
−0.3V
to 6V
−18V
to 0.3V
Supply Voltage, VIN, VCC ---------------------------------------------------------------------------------------
Switch Voltage, SW -----------------------------------------------------------------------------------------------
< 10ns ----------------------------------------------------------------------------------------------------------------
BOOT to SW --------------------------------------------------------------------------------------------------------
VREG5 to VIN or VCC --------------------------------------------------------------------------------------------
Other Pins Voltage -------------------------------------------------------------------------------------------------
−0.3V
to 21V
Power Dissipation, P
D
@ T
A
= 25°C
WQFN-16L 3x3 ----------------------------------------------------------------------------------------------------- 2.1W
Package Thermal Resistance (Note 2)
WQFN-16L 3x3,
θ
JA
------------------------------------------------------------------------------------------------ 47.4°C/W
WQFN-16L 3x3,
θ
JC
----------------------------------------------------------------------------------------------- 7.5°C/W
Junction Temperature Range ------------------------------------------------------------------------------------- 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 Voltage, VIN ----------------------------------------------------------------------------------------------- 4.5V to 18V
Junction Temperature Range -------------------------------------------------------------------------------------
−40°C
to 125°C
Ambient Temperature Range -------------------------------------------------------------------------------------
−40°C
to 85°C
Electrical Characteristics
Parameter
Supply Current
Shutdown Current
Quiescent Current
Logic Threshold
EN Voltage
Logic-High
Logic-Low
I
SHDN
I
Q
(V
IN
= 12V, T
A
=
−40°C
to 85°C, unless otherwise specified)
Symbol
Test Conditions
T
A
= 25C, V
EN
= 0V
T
A
= 25C, V
EN
= 5V, V
FB
= 0.8V
Min
--
--
2
--
Typ
1
1
--
--
Max
10
1.3
18
0.4
Unit
A
mA
V
V
FB
Voltage and Discharge Resistance
Feedback Threshold Voltage
Feedback Input Current
VS Discharge Resistance
V
REG5
Output
V
REG5
Output Voltage
Line Regulation
Load Regulation
Output Current
I
VREG5
V
REG5
T
A
= 25C, 6V
V
IN
18V,
0 < I
VREG5
5mA
6V
V
IN
18V, I
VREG5
= 5mA
0
I
VREG5
5mA
V
IN
= 6V, V
REG5
= 4V, T
A
= 25C
4.8
--
--
--
5.1
--
--
70
5.4
20
100
--
V
mV
mV
mA
V
FB
I
FB
R
DIS
T
A
= 25C
T
A
=
40C
to 85C
V
FB
= 0.8V, T
A
= 25C
V
EN
= 0V, V
S
= 0.5V
0.757
0.755
--
--
0.765 0.773
--
0.01
50
0.775
0.1
100
V
A
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS2853A/B-02 October 2016
www.richtek.com
3
RT2853A/B
Parameter
R
DS(ON)
Switch On
Resistance
Current Limit
Current Limit
Thermal Shutdown
Thermal Shutdown Threshold
On-Time Timer Control
On-Time
Minimum Off-Time
Soft-Start
SS Charge Current
SS Discharge Current
UVLO
UVLO Threshold
Hysteresis
Power Good
PGOOD Threshold
PGOOD Sink Current
OVP Trip Threshold
OVP Prop Delay
UVP Trip Threshold
UVP Hysteresis
UVP Prop Delay
UVP Enable Delay
t
UVPEN
Relative to Soft-Start Time
V
FB
Rising
V
FB
Falling
PGOOD = 0.5V
OVP Detect
85
--
2.5
115
--
65
--
--
--
90
85
5
120
5
70
10
250
t
SS
x 1.7
95
--
--
125
--
75
--
--
--
%
mA
%
s
%
s
ms
Wake Up V
REG5
3.6
0.13
3.85
0.35
4.1
0.47
V
V
SS
= 0V
V
SS
= 0.5V
1.4
0.1
2
0.2
2.6
--
A
mA
t
ON
t
OFF(MIN)
V
OUT
= 1.05V
V
FB
= 0.7V, T
A
= 25C
--
--
135
260
--
310
ns
ns
T
SD
Shutdown Temperature
--
--
150
20
--
--
Thermal Shutdown Hysteresis
T
SD
C
I
LIM
L
SW
= 1.4H
4
4.5
6
A
High-Side
Low-Side
R
DS(ON)_H
R
DS(ON)_L
T
A
= 25C (V
BOOT
V
SW
) = 5.5V
T
A
= 25C
--
--
110
30
--
--
m
Symbol
Test Conditions
Min
Typ
Max
Unit
Output Under Voltage and Over Voltage Protection
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
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS2853A/B-02 October 2016
RT2853A/B
Typical Operating Characteristics
Efficiency vs. Load Current
100
90
80
Efficiency vs. Load Current
100
90
RT2853A
RT2853B
Efficiency (%)
60
50
40
30
20
10
0
0.001
0.01
0.1
1
Efficiency (%)
70
V
OUT
= 5V
V
OUT
= 1.05V
80
70
60
50
40
30
20
V
OUT
= 5V
V
OUT
= 1.05V
V
IN
= 12V
10
10
0
0.001
0.01
0.1
1
V
IN
= 12V
10
Load Current (A)
Load Current (A)
Output Voltage vs. Load Current
1.10
Output Voltage vs. Load Current
1.10
RT2853A
RT2853B
1.08
1.08
Output Voltage (V)
1.06
Output Voltage (V)
V
IN
= 12V, V
OUT
= 1.05V, I
OUT
= 0 to 3A
1.06
1.04
1.04
1.02
1.02
V
IN
= 12V, V
OUT
= 1.05V, I
OUT
= 0 to 3A
1.00
3
0
0.5
1
1.5
2
2.5
3
1.00
0
0.5
1
1.5
2
2.5
Load Current (A)
Load Current (A)
Switching Frequency vs. Load Current
800
Switching Frequency vs. Load Current
800
RT2853A
RT2853B
Switching Frequency (kHz)
1
700
600
500
400
300
200
100
Switching Frequency (kHz)
1
V
IN
= 12V, V
OUT
= 1.05V, I
OUT
= 0 to 3A
700
600
500
400
300
200
100
V
IN
= 12V, V
OUT
= 1.05V, I
OUT
= 0 to 3A
0
3
0
0.5
1
1.5
2
2.5
3
0
0
0.5
1
1.5
2
2.5
Load Current (A)
Load Current (A)
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS2853A/B-02 October 2016
www.richtek.com
5
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