®
RT6201A/B
4A, 18V, 650kHz, ACOT
TM
Synchronous Step-Down Converter
General Description
The RT6201A/B is a synchronous step-down DC/DC
converter with Advanced Constant On-Time (ACOT
TM
)
mode control. It achieves high power density to deliver up
to 4A output current from a 4.5V to 18V input supply. The
proprietary ACOT
TM
mode offers an optimal transient
response over a wide range of loads and all kinds of ceramic
capacitors, which allows the device to adopt very low ESR
output capacitor for ensuring performance stabilization. In
addition, RT6201A/B keeps an excellent constant
switching frequency under line and load variation and the
integrated synchronous power switches with the ACOT
TM
mode operation provides high efficiency in whole output
current load range. Cycle-by-cycle current limit provides
an accurate protection by a valley detection of low side
MOSFET and external soft-start setting eliminates input
current surge during startup. Protection functions include
thermal shutdown for RT6201A/B.
The RT6201A/B are available in the SOP-8 (Exposed Pad)
package.
Features
ACOT
TM
Mode Enables Fast Transient Response
4.5V to 18V Input Voltage Range
4A Output Current
50mΩ Internal Low Side N-MOSFET
Ω
Advanced Constant On-Time Control
Support All Ceramic Capacitors
Up to 95% Efficiency
650kHz Switching Frequency at all Load Current
(RT6201B)
Discontinuous Operating Mode at Light Load
(RT6201A)
Adjustable Output Voltage from 0.765V to 8V
Adjustable Soft-Start
Cycle-by-Cycle Current Limit
Input Under Voltage Lockout
Thermal Shutdown
RoHS Compliant and Halogen Free
Applications
Pin Configurations
(TOP VIEW)
EN
FB
VREG5
SS
2
3
4
8
VIN
BOOT
SW
GND
GND
9
7
6
5
Industrial and Commercial Low Power Systems
Computer Peripherals
LCD Monitors and TVs
Green Electronics/Appliances
Point of Load Regulation for High-Performance DSPs,
FPGAs, and ASICs
SOP-8 (Exposed Pad)
Simplified Application Circuit
RT6201A/B
V
IN
VIN
SW
BOOT
Enable
EN
VREG5
SS
FB
GND
V
OUT
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS6201A/B-00
December 2013
www.richtek.com
1
RT6201A/B
Ordering Information
RT6201A/B
Package Type
SP : SOP-8 (Exposed Pad-Option 2)
Lead Plating System
G : Green (Halogen Free and Pb Free)
UVP Trim Operation
H : Hiccup
PSM/PWM Mode
A : PSM Mode
B : PWM Mode
Note :
Richtek products are :
½
Marking Information
RT6201AHGSP
RT6201AHGSP : Product Number
RT6201AH
GSPYMDNN
YMDNN : Date Code
RT6201BHGSP
RT6201BHGSP : Product Number
RT6201BH
GSPYMDNN
YMDNN : Date 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.
½
Functional Pin Description
Pin No.
1
Pin Name
EN
Pin Function
Enable Control Input. A logic-high enables the converter; a logic-low forces the
IC into shutdown mode reducing the supply current to less than 10A.
Feedback Voltage Input. It is used to regulate the output of the converter to a set
value via an external resistive voltage divider. The feedback threshold voltage is
0.765V typically.
Internal Regulator Output. Connect a 1F capacitor to GND to stabilize output
voltage.
Soft-Start Time Setting. Connect an external capacitor between this pin and GND to
set the soft- start time.
Power Ground. The exposed pad must be soldered to a large PCB and
connected to GND for maximum power dissipation.
Switch Node. Connect this pin to an external L-C filter.
Bootstrap Supply for High Side Gate Driver. Connect a 0.1F capacitor between
the BOOT and SW pin.
Power Input. The input voltage range is from 4.5V to 18V. Must bypass with a
suitably large (10F x 2) ceramic capacitor.
2
FB
3
4
5, 9
(Exposed Pad)
6
7
8
VREG5
SS
GND
SW
BOOT
VIN
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS6201A/B-00
December 2013
RT6201A/B
Function Block Diagram
VREG5
BOOT
EN
POR &
Reg
VBIAS
OC
UV & OV
SW
V
REG5
6µA
Ripple
Gen.
V
REF
Min.
Off-Time
VREG5
VIN
SW
Control
Driver
GND
ZC
V
IN
On-Time
FB
SS
FB
+
-
-
Comparator
Operation
The RT6201A/B is a synchronous step-down converter
with advanced constant on-time control mode. Using the
ACOT
TM
control mode can reduce the output capacitance
and provide fast transient response. It can minimize the
component size without additional external compensation
network.
Internal Regulator
The regulator provides 5V power to supply the internal
control circuit. Connecting a 1μF ceramic capacitor for
decoupling and stability is required.
Soft-Start
In order to prevent the converter output voltage from
overshooting during the startup period, the soft-start
function is necessary. The soft-start time is adjustable
and can be set by an external capacitor.
UVLO Protection
To protect the chip from operating at insufficient supply
voltage, the UVLO is needed. When the input voltage of
VIN is lower than the UVLO falling threshold voltage, the
device will be latch-off.
Thermal Shutdown
When the junction temperature exceeds the OTP
threshold value, the IC will shut down the switching
operation. Once the junction temperature cools down and
is lower than the OTP lower threshold, the converter will
automatically resume switching
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS6201A/B-00
December 2013
www.richtek.com
3
RT6201A/B
Absolute Maximum Ratings
(Note 1)
−0.3V
to 20V
−0.8V
to (V
IN
+ 0.3V)
−5V
to 25V
−0.3V
to 6V
−0.3V
to 20V
−0.3V
to 6V
Supply Voltage, VIN -----------------------------------------------------------------------------------------------
Switch Voltage, SW -----------------------------------------------------------------------------------------------
< 10ns ----------------------------------------------------------------------------------------------------------------
BOOT to SW --------------------------------------------------------------------------------------------------------
EN ----------------------------------------------------------------------------------------------------------------------
Other Pins ------------------------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
SOP-8 (Exposed Pad) -------------------------------------------------------------------------------------------- 2.041W
Package Thermal Resistance (Note 2)
SOP-8 (Exposed Pad),
θ
JA
--------------------------------------------------------------------------------------- 49°C/W
SOP-8 (Exposed Pad),
θ
JC
-------------------------------------------------------------------------------------- 15°C/W
Junction Temperature Range ------------------------------------------------------------------------------------- 150°C
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------ 260°C
Storage Temperature Range -------------------------------------------------------------------------------------
−65°C
to 150°C
(Note 3)
Recommended Operating Conditions
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
(V
IN
= 12V, T
A
= 25°C, unless otherwise specified)
Parameter
Supply Current
Shutdown Current
Quiescent Current
Logic Threshold
EN Input Voltage
V
FB
Voltage
Feedback Threshold Voltage
Feedback Input Current
V
REG5
Output
V
REG5
Output Voltage
Line Regulation
Load Regulation
Output Current
Logic-High
Logic-Low
Symbol
I
SHDN
I
Q
V
EN
= 0V
Test Conditions
Min
--
--
2
--
Typ
1
1
--
--
Max
10
1.3
18
0.4
Unit
A
mA
V
EN
= 5V, V
FB
= 0.8V
V
V
FB
I
FB
V
REG5
T
A
= 25C
T
A
=
40C
to 85C
V
FB
= 0.8V
6V
V
IN
18V, 0 < I
VREG5
< 5mA
6V
V
IN
18V, I
VREG5
= 5mA
0
I
VREG5
5mA
0.757
0.755
--
4.8
--
--
--
0.765 0.773
--
0.01
5.1
--
--
70
0.775
0.1
5.4
20
100
--
V
A
V
mV
mV
mA
I
VREG5
V
IN
= 6V, V
REG5
= 4V
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS6201A/B-00
December 2013
RT6201A/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
Output Under Voltage and Over Voltage Protection
OVP Trip Threshold
OVP Prop Delay
UVP Trip Threshold
UVP Hysteresis
UVP Prop Delay
UVP Enable Delay
t
UVPEN
Relative to Soft-Start Time
OVP Detect
115
--
65
--
--
--
120
5
70
10
250
t
SS
x 1.7
125
--
75
--
--
--
%
s
%
s
ms
Wake Up V
REG5
3.6
0.16
3.85
0.35
4.1
0.47
V
V
SS
= 0V
V
SS
= 0.5V
--
0.1
6
0.2
--
--
A
mA
t
ON
t
OFF(MIN)
V
IN
= 12V, V
OUT
= 1.05V
V
FB
= 0.7V
--
--
135
260
--
310
ns
ns
T
SD
Shutdown Temperature
--
--
150
20
--
--
Thermal Shutdown Hysteresis
T
SD
C
I
LIM
4.7
5.4
7.5
A
High-Side
Low-Side
R
DS(ON)_H
R
DS(ON)_L
(V
BOOT
V
SW
) = 5.5V
--
--
120
50
--
--
m
Symbol
Test Conditions
Min
Typ
Max
Unit
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
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS6201A/B-00
December 2013
www.richtek.com
5
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