RT6212A/B
2A, 18V, 500kHz, ACOT
TM
Step-Down Converter
General Description
The RT6212A/B is a high-efficiency, monolithic
synchronous step-down DC-DC converter that can
deliver up to 2A output current from a 4.5V to 18V input
supply. The RT6212A/B adopts ACOT 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-current protection, and thermal
shutdown.
Features
Integrated 163m/86m MOSFETs
4.5V to 18V Supply Voltage Range
500kHz Switching Frequency
ACOT Control
Feedback Reference Voltage 0.8V ± 1.5%
Feedback Reference Voltage 0.765V ± 1.5%
Internal Start-Up into Pre-Biased Outputs
Compact Package : TSOT-23-6 Pin
Input Under-Voltage Lockout
Over-Current Protection and Hiccup
Applications
Ordering Information
RT6212A/B
(
)
Package Type
J6F : TSOT-23-6 (FC)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Reference Voltage
None : V
REF
= 0.8V
R : V
REF
= 0.765V
UVP Option
H : Hiccup
PSM/PWM
A : PSM/PWM
B : Force-PWM
Set-Top Boxes
Portable TVs
Access Point Routers
DSL Modems
LCD TVs
Marking Information
RT6212AHRGJ6F
2W= : Product Code
DNN : Date Code
2W=DNN
RT6212BHRGJ6F
2V=DNN
RT6212AHGJ6F
2V= : Product Code
DNN : Date Code
Note :
Richtek products are :
0B=DNN
RT6212BHGJ6F
0B= : Product Code
DNN : Date Code
RoHS compliant and compatible with the current
requirements of IPC/JEDEC J-STD-020.
0A= : Product Code
DNN : Date Code
Suitable for use in SnPb or Pb-free soldering
processes.
0A=DNN
Simplified Application Circuit
V
IN
C
IN
LX
Enable
EN
GND
FB
R2
R1
C
FF
C
OUT
RT6212A/B
BOOT
VIN
C
BOOT
L
V
OUT
Copyright © 2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS6212A/B-08
August 2018
www.richtek.com
1
RT6212A/B
Pin Configuration
(TOP VIEW)
BOOT EN
6
5
FB
4
2
3
GND LX VIN
TSOT-23-6 (FC)
Functional Pin Description
Pin No.
1
2
3
4
5
6
Pin Name
GND
LX
VIN
FB
EN
BOOT
Pin Function
System ground. Provides the ground return path for the control circuitry and
low-side power MOSFET.
Switch node. LX is the switching node that supplies power to the output and
connect the output LC filter from LX to the output load.
Power input. Supplies the power switches of the device.
Feedback voltage input. This pin is used to set the desired output voltage via
an external resistive divider. The feedback voltage is 0.765V/0.8V typically.
Enable control input. Floating this pin or connecting this pin to GND can disable
the device and connecting this pin to logic high can enable the device.
Bootstrap supply for high-side gate driver. Connect a 100nF or greater
capacitor from LX to BOOT to power the high-side switch.
Functional Block Diagram
VIN
6.5K
EN
3V
VEN_
REF
LX
-
+
UVLO
On-
Time
OC
Shutdown
Comparator
Internal
Regulator
VCC
PVCC
BOOT
UGATE
Control
Power
Stage &
Dead-time
Control
LX
UV
Protection
VCC
Ripple
Gen.
FB
+
+
-
LGATE
MIN OFF
Comparator
VCC
VIBIAS
VRef
GND
Copyright © 2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS6212A/B-08
August 2018
RT6212A/B
Operation
The RT6212A/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.
Soft-Start (SS)
The RT6212A/B provides an internal soft-start feature
for inrush control. At power up, the internal capacitor is
charged by an internal current source I
SS
to generate a
soft-start ramp voltage as a reference voltage to the
PWM comparator. The device will initiate switching and
the output voltage will smoothly ramp up to its targeted
regulation voltage only after this ramp voltage is
greater than the feedback voltage V
FB
to ensure the
converters have a smooth start-up. The output voltage
starts to rise in 85s from EN rising, and the soft-start
ramp-up time (V
FB
from 0V to V
REF
) is 1ms.
operation. Once the junction temperature cools down
and is lower than the OTP lower threshold, the
converter will autocratically resume switching.
Output Under-Voltage Protection and Hiccup Mode
The RT6212A/B includes output under-voltage
protection (UVP) against over-load or short-circuited
condition by constantly monitoring the feedback
voltage V
FB
. If V
FB
drops below the under-voltage
protection trip threshold (typically 50% of the internal
feedback reference voltage), the UV comparator will go
high to turn off both the internal high-side and low-side
MOSFET switches.
If the output under-voltage condition continues for a
period of time, the RT6212A/B will enter output
under-voltage protection with hiccup mode. During
hiccup mode, the IC will shut down for t
HICCUP_OFF
(3.6ms), and then attempt to recover automatically for
t
HICCUP_ON
(1.2ms). Upon completion of the soft-start
sequence, if the fault condition is removed, the
converter will resume normal operation; otherwise,
EN
such cycle for auto-recovery will be repeated until the
fault condition is cleared. Hiccup mode allows the
circuit to operate safely with low input current and
power dissipation, and then resume normal operation
as soon as the over-load or short-circuit condition is
removed.
Resume normal
operation
t
HICCUP_ON
= 1.2ms
t
HICCUP_OFF
= 3.6ms
Fault condition
removed
t
1ms
FB
1ms
85μs
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
VOUT
Abnormal case
detected (UV)
LX
t
Copyright © 2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS6212A/B-08
August 2018
www.richtek.com
3
RT6212A/B
Absolute Maximum Ratings
(Note 1)
Supply Input Voltage ---------------------------------------------------------------------------------
0.3V
to 20V
Switch Node Voltage, LX ----------------------------------------------------------------------------
0.3V
to (V
IN
+ 0.3V)
< 50ns ----------------------------------------------------------------------------------------------------
6V
to 25V
BOOT Pin Voltage ------------------------------------------------------------------------------------
(V
LX
– 0.3V) to (V
IN
+ 6.3V)
Other Pins -----------------------------------------------------------------------------------------------
0.3V
to 6V
Power Dissipation, P
D
@ T
A
= 25C
TSOT-23-6 (FC) ---------------------------------------------------------------------------------------
1.667W
Package Thermal Resistance
(Note 2)
TSOT-23-6 (FC),
JA
---------------------------------------------------------------------------------
60C/W
TSOT-23-6 (FC),
JC
---------------------------------------------------------------------------------
8C/W
Lead Temperature (Soldering, 10 sec.) ----------------------------------------------------------
260C
Junction Temperature --------------------------------------------------------------------------------
150C
Storage Temperature Range -----------------------------------------------------------------------
65C
to 150C
ESD Susceptibility
(Note 3)
HBM (Human Body Model) -------------------------------------------------------------------------
2kV
Recommended Operating Conditions
(Note 4)
Supply Input Voltage ---------------------------------------------------------------------------------
4.5V
to 18V
Ambient Temperature Range-----------------------------------------------------------------------
40C
to 85C
Junction Temperature Range ----------------------------------------------------------------------
40C
to 125C
Electrical Characteristics
(V
IN
= 12V, T
A
= 25C, unless otherwise specified)
Parameter
Supply Voltage
VIN Supply Input Operating
Voltage
Under-Voltage Lockout
Threshold
Under-Voltage Lockout
Threshold Hysteresis
Shutdown Current
Quiescent Current
Soft-Start
Soft-Start Time
Enable Voltage
Symbol
Test Conditions
Min
Typ
Max
Unit
V
IN
V
UVLO
V
UVLO
I
SHDN
I
Q
t
SS
V
EN_R
V
EN
rising, RT6212A/BHGJ6F
V
EN
falling, RT6212A/BHGJ6F
V
EN
rising, RT6212A/BHRGJ6F
V
EN
= 0V
V
EN
= 2V, V
FB
= 0.85V
RT6212A/BHGJ6F
RT6212A/BHRGJ6F
4.5
3.6
3.45
--
--
--
--
1.4
1.18
1.33
--
3.9
3.75
340
--
0.5
1000
1.5
1.28
1.43
18
4.2
4.05
--
5
--
--
1.6
1.38
1.53
V
V
mV
µA
mA
µs
Enable Voltage Threshold
V
EN_F
V
EN_R
V
Copyright © 2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS6212A/B-08
August 2018
RT6212A/B
Parameter
Symbol
V
EN_F
Feedback Voltage
4.5V ≤ V
IN
≤ 18V,
RT6212A/BHGJ6F
4.5V ≤ V
IN
≤ 18V,
RT6212A/BHRGJ6F
V
BOOT
− V
LX
= 4.8V
0.788
0.753
0.8
0.765
0.812
V
0.777
Test Conditions
V
EN
falling, RT6212A/BHRGJ6F
Min
1.11
Typ
1.21
Max
1.31
Unit
Feedback Reference Voltage
V
REF
Internal MOSFET
High-Side On-Resistance
Low-Side On-Resistance
Current Limit
High-Side Switch Current Limit I
LIM_H
Low-Side Switch Valley Current
I
LIM_L
Limit
Switching Frequency
Switching Frequency
On-Time Timer Control
Minimum On-Time
Minimum Off-Time
t
ON_MIN
t
OFF_MIN
OVP detect
35
185
60
240
85
315
ns
f
SW
400
500
640
kHz
--
2.6
5.8
3.3
--
--
A
R
DS(ON)_H
R
DS(ON)_L
--
--
163
86
--
--
mΩ
Output Under-Voltage and Over-Voltage Protections
OVP Trip Threshold
OVP Propagation Delay
UVP Trip Threshold
UVP Propagation Delay
Thermal Shutdown
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
T
SD
T
SD
--
--
150
20
--
--
°C
UVP detect
Hysteresis
--
--
45
--
--
125
10
50
10
5
--
--
55
--
--
%
µs
%
µs
Note 1.
Stresses beyond those listed under “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.
JA
is measured under natural convection (still air) at T
A
= 25C 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.
JA
is measured at the lead of the package.
Note 3.
Devices are ESD sensitive. Handling precaution recommended.
Note 4.
The device is not guaranteed to function outside its operating conditions.
Copyright © 2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS6212A/B-08
August 2018
www.richtek.com
5
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