®
RT6222A/B
2.5A, 18V, 500kHz ACOT
TM
Synchronous Step-Down Converter
General Description
The RT6222A/B is a synchronous step-down converter
with Advanced Constant On-Time (ACOT
TM
) control mode.
The ACOT
TM
provides a very fast transient response with
few external components. The low impedance internal
MOSFET supports high efficiency operation with wide input
voltage range from 4.3V to 18V. The proprietary circuit of
the RT6222A/B enables to support all ceramic capacitors.
The output voltage can be adjusted between 0.6V and 8V.
Features
4.3V to 18V Input Voltage Range
2.5A Output Current
Advanced Constant On-Time Control
Fast Transient Response
Support All Ceramic Capacitors
Up to 95% Efficiency
500kHz Switching Frequency
Adjustable Output Voltage from 0.6V to 8V
Cycle-by-Cycle Current Limit
Input Under-Voltage Lockout
Hiccup Mode Under-Voltage Protection
Thermal Shutdown
Power Saving Mode for High Efficiency at Light
Load
Low Output Voltage Ripple at Light Load
High Side Over Current Limit
RoHS Compliant and Halogen Free
Ordering Information
RT6222A/B
Package Type
J6F : TSOT-23-6 (FC)
Lead Plating System
G : Green (Halogen Free and Pb Free)
UVP Option
H: Hiccup
PSM/PWM
A : PSM/PWM
B : Force-PWM
Note :
Richtek products are :
½
Applications
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
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
Simplified Application Circuit
V
IN
RT6222A/B
BOOT
VIN
SW
Enable
EN
FB
V
OUT
GND
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS6222A/B-00 October 2015
www.richtek.com
1
RT6222A/B
Pin Configurations
(TOP VIEW)
SW VIN EN
6
5
2
4
3
Marking Information
RT6222AHGJ6F
1K= : Product Code
1K=DNN
DNN : Date Code
RT6222BHGJ6F
BOOT GND FB
TSOT-23-6 (FC)
1J=DNN
1J= : Product Code
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. Connect to external L-C filter.
Function 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
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS6222A/B-00 October 2015
RT6222A/B
Operation
The RT6222A/B 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 RT6222A/B 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
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS6222A/B-00 October 2015
www.richtek.com
3
RT6222A/B
Absolute Maximum Ratings
(Note 1)
−0.3V
to 20V
−0.3V
to 20V
−5V
to 25V
−0.3V
to 6V
−0.3V
to 26V
−0.3V
to 6V
VIN to GND -------------------------------------------------------------------------------------------------------------------
SW to GND ------------------------------------------------------------------------------------------------------------------
<10ns -------------------------------------------------------------------------------------------------------------------------
BOOT to SW ----------------------------------------------------------------------------------------------------------------
BOOT to GND ---------------------------------------------------------------------------------------------------------------
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
Oscillator Frequency
Maximum Duty Cycle
Minimum On-Time
Feedback Threshold Voltage
EN Input Threshold
Logic-High
Logic-Low
High-Side
Low-Side
Symbol
I
SHDN
I
Q
R
DS(ON)_H
R
DS(ON)_L
f
SW
D
MAX
t
ON
V
FB
V
EN_H
V
EN_L
V
UVLO
Test Conditions
V
EN
= 0V
V
EN
= 2V, V
FB
= 1V
V
BOOTSW
= 4.8V
V
IN
= 5V
Min
--
--
--
--
--
--
--
Typ
--
0.5
150
90
500
90
60
600
--
---
3.9
340
800
160
Max
4
--
--
--
--
--
--
609
--
0.4
4.25
--
--
--
Unit
A
mA
m
kHz
%
ns
mV
V
V
mV
s
C
In CCM Mode
591
1.5
--
VIN Under-Voltage Lockout
Threshold
VIN Under-Voltage Lockout
Threshold Hysteresis
Soft-Start Time
Thermal Shutdown Threshold
VIN Rising
3.55
--
t
SS
T
SD
--
--
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS6222A/B-00 October 2015
RT6222A/B
Parameter
Thermal Shutdown Hysteresis
V
OUT
Discharge Resistance
Output Under-Voltage Trip
Threshold
Output Under-Voltage Delay
Time
Low-Side Switch Valley
Current Limit
High-Side Switch Peak
Current Limit
Symbol
T
SD
R
DISCHG
EN = 0V, V
OUT
= 0.5V
UVP detect
Hysteresis
Test Conditions
Min
--
--
70
--
--
I
LIM_L
I
LIM_H
2.7
--
Typ
20
50
75
10
250
3.4
5.5
Max
--
100
80
--
--
4
--
Unit
C
%
s
A
A
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. The first
layer of copper area is filled.
θ
JC
is measured at the top 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.
DS6222A/B-00 October 2015
www.richtek.com
5
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