®
RT6224C
3A, 18V, 1.4MHz ACOT
TM
Synchronous Step-Down Converter
General Description
The
RT6224C is a high-efficiency, monolithic synchronous
step-down DC-DC converter that can deliver up to 3A output
current from a 4.3V to 18V input supply. The RT6224C
adopts ACOT
TM
architecture to allow the transient
response to be improved and keep in constant frequency.
Cycle-by-cycle current limit provides protection against
shorted outputs and soft-start eliminates input current
surge during start-up. Fault conditions also include output
under-voltage protection, output over-voltage protection,
and thermal
shutdown.
Features
Small Output Voltage at Light Load
High-Side Over-Current Limit
Integrated 90mΩ/45mΩ MOSFETs
Ω
Ω
4.3V to 18V Supply Voltage Range
1.4MHz Switching Frequency
ACOT
TM
Control
0.6V
±
1.5% Voltage Reference
Monotonic Start-Up into Pre-biased Outputs
Applications
Set Top Box
Portable TV
Access Point Router
DSL Modem
LCD TV
Ordering Information
RT6224C
Package Type
J6F : TSOT-23-6 (FC)
Lead Plating System
G : Green (Halogen Free and Pb Free)
UVP Option
H : Hiccup
PSM/PWM
C : PSM/PWM
Note :
Richtek products are :
½
Pin Configuration
(TOP VIEW)
SW VIN EN
6
5
2
4
3
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.
BOOT GND FB
TSOT-23-6 (FC)
½
Simplified Application Circuit
RT6224C
BOOT
SW
Enable
EN
FB
V
OUT
V
IN
VIN
GND
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS6224C-00 August 2016
www.richtek.com
1
RT6224C
Marking Information
1Y= : Product Code
1Y=DNN
DNN : Date Code
Functional Pin Description
Pin No.
1
2
3
4
5
6
Pin Name
BOOT
GND
FB
EN
VIN
SW
Pin Function
Bootstrap supply for high-side gate driver. Connect a 0.1F ceramic capacitor
between the BOOT and SW pins.
Power ground.
Feedback voltage input. The pin is used to set the output voltage of the converter
via a resistive divider. The converter regulates V
FB
to 0.6V.
Enable control input. Connect EN to a logic-high voltage to enable the IC or to a
logic-low voltage to disable. Do not leave this high impedance input unconnected.
Power input. The input voltage range is from 4.3V to 18V. Must bypass with a
suitable large ceramic capacitor at this pin.
Switch node. Connected to external L-C filter.
Functional Block Diagram
BOOT
V
IN
Reg
VIBIAS
VCC
V
REF
Min off
VCC
UGATE
Control
UV
VCC
SW
Ripple
Gen.
+
+
-
Comparator
EN
GND SW
V
IN
On-Time
SW
Driver
LGATE
GND
SW
VIN
OC
FB
EN
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS6224C-00 August 2016
RT6224C
Operation
The RT6224C is a synchronous step-down converter with
advanced constant on-time control mode. Using the ACOT
control mode can reduce the output capacitance and
perform fast transient response. It can minimize the
component size without additional external compensation
network.
Current Protection
The inductor current is monitored via the internal switches
cycle-by-cycle. Once the output voltage drops under UV
threshold, the RT6224C will enter
hiccup mode.
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 lockout.
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
autocratically resume switching.
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS6224C-00 August 2016
www.richtek.com
3
RT6224C
Absolute Maximum Ratings
(Note 1)
−0.3V
to 20V
−0.3V
to (V
IN
+ 0.3V)
−5V
to 25V
(V
SW
−
0.3V) to (V
SW
+ 6V)
−0.3V
to 6V
VIN to GND -----------------------------------------------------------------------------------------------------
SW to GND ----------------------------------------------------------------------------------------------------
<10ns -----------------------------------------------------------------------------------------------------------
BOOT to GND -------------------------------------------------------------------------------------------------
All Other Pins -------------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
TSOT-23-6 (FC) ----------------------------------------------------------------------------------------------- 1.429W
Package Thermal Resistance (Note 2)
TSOT-23-6 (FC),
θ
JA
------------------------------------------------------------------------------------------ 70°C/W
TSOT-23-6 (FC),
θ
JC
----------------------------------------------------------------------------------------- 15°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
(Note 4)
Recommended Operating Conditions
Supply Input Voltage, VIN ---------------------------------------------------------------------------------- 4.3V 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
Shutdown Current
Quiescent Current
Switch-On Resistance
Low-Side Current Limit
High-Side Current Limit
Oscillator Frequency
Maximum Duty Cycle
Minimum On-Time
Feedback Voltage
EN Rising Threshold
EN Falling Threshold
VIN Under-Voltage Lockout
Threshold-Rising
VIN Under-Voltage Lockout
Threshold-Hysteresis
High-Side
Low-Side
I
Q
Symbol
I
SHDN
R
DS(ON)_H
R
DS(ON)_L
I
LIM_L
I
LIM_H
f
SW
D
MAX
t
ON(MIN)
V
FB
V
EN_H
V
EN_L
Conditions
V
EN
= 0V
V
EN
= 2V, V
FB
= 1V
V
BST
SW
= 4.8V
V
IN
= 5V
Min
--
--
--
--
3.2
--
--
--
--
591
1.5
--
3.55
--
Typ
--
0.5
90
45
3.9
6.5
1400
80
40
600
--
--
3.9
340
Max
4
--
105
65
4.5
--
--
--
--
609
--
0.4
4.25
--
Unit
A
mA
m
A
A
kHz
%
ns
mV
V
V
V
mV
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS6224C-00 August 2016
RT6224C
Parameter
Soft-Start Period
Thermal Shutdown
Thermal Hysteresis
V
OUT
Discharge Resistance
Output Under-Voltage Trip Threshold
Output Under-Voltage Delay
R
DISCHG
EN = 0V, V
OUT
= 0.5V
UVP detect
Hysteresis
Symbol
t
SS
Conditions
Min
--
--
--
--
70
--
--
Typ
800
160
20
50
75
10
250
Max
--
--
--
100
80
--
--
Unit
s
C
C
%
s
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 under natural convection (still air) at T
A
= 25°C with the component mounted on a high effective-
thermal-conductivity four-layer test board on a JEDEC 51-7 thermal measurement standard. The first layer is filled with
copper.
θ
JC
is measured at the lead 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.
DS6224C-00 August 2016
www.richtek.com
5
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