®
RT6217E
3A, 24V, 500kHz, ACOT
TM
Step-Down Converter
General Description
The RT6217E is a high-efficiency, monolithic synchronous
step-down
DC-DC converter that can deliver up to 3A output
current from a 4.5V to 24V input supply. The RT6217E
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 and thermal shutdown.
Features
Integrated 85mΩ/40mΩ MOSFETs
4.5V to 24V Supply Voltage Range
500kHz Switching Frequency
ACOT
TM
Control
0.791V
±
1.5% Voltage Reference
Monotonic Start-Up into Pre-biased Outputs
Output Adjustable from 0.791V to 6V
Compact package : TSOT 23-8 (FC)
Applications
Ordering Information
RT6217E
Package Type
J8F : TSOT-23-8 (FC)
Lead Plating System
G : Green (Halogen Free and Pb Free)
UVP Option
H : Hiccup
Note :
Richtek products are :
½
Set Top Box
Portable TV
Access Point Router
DSL Modem
LCD TV
Pin Configurations
(TOP VIEW)
BOOT
5
4
NC
7
2
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.
8
½
MODE
VIN
SW
EN
6
3
FB
Marking Information
0Q= : Product Code
TSOT-23-8 (FC)
0Q=DNN
DNN : Date Code
Simplified Application Circuit
RT6217E
V
IN
C
IN
SW
R1
Mode
MODE
FB
GND
R2
C
FF
C
OUT
VIN
BOOT
R3
C
BOOT
L
Enable
EN
V
OUT
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS6217E-02 July 2016
GND
www.richtek.com
1
RT6217E
Functional Pin Description
Pin No.
1
Pin Name
MODE
Pin Function
Mode Selection Input. Set MODE pin high will force RT6217E into CCM.
Connect MODE to VIN with a 100k resistor for CCM application. Connect
MODE pin to ground to force RT6217E into Pulse Skipping Mode for light
load. Do not float MODE pin.
Input Voltage. Support 4.5 to 24V Input Voltage. Must bypass with a suitable
large ceramic capacitor at this pin.
Switch Node. Connect to external L-C filter.
System Ground.
Bootstrap, Supply for High-Side Gate Driver. Connect a 0.1F ceramic
capacitor between the BOOT and SW pins.
Buck Enable. High = Enable.
This pin is left to float.
Feedback Input. The pin is used to set the output voltage of the converter to
regulate to the desired via a resistive divider.
2
3
4
5
6
7
8
VIN
SW
GND
BOOT
EN
NC
FB
Function Block Diagram
NC
MODE
BOOT
VIN
VIN
Reg
VCC
Minoff
3.5V
VCC
UGATE
OC
Control
Driver
LGATE
UV
GND
GND SW
SW
VIBIAS
VREF
VCC
SW
Ripple
Gen.
+
+
-
Comparator
FB
EN
VIN
On
Time
SW
EN
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS6217E-02 July 2016
RT6217E
Operation
The RT6217E is a high-efficiency, monolithic synchronous
step-down DC-DC converter that can deliver up to 3A output
current from a 4.5V to 24V input supply. Using the
ACOT
TM
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 RT6217E will enter hiccup mode.
Hiccup Mode
The RT6217E use hiccup mode for UVP. When the
protection function is triggered, the IC will shut down for a
period of time and then attempt to recover automatically.
Hiccup mode allows the circuit to operate safely with low
input current and power dissipation, and then resume
normal operation as soon as the overload or short circuit
is removed.
Input Under-Voltage Lockout
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.
Shut-Down, Start-up and Enable (EN)
The enable input (EN) has a logic-low level. When V
EN
is
below this level the IC enters shutdown mode. When V
EN
exceeds its logic-high level the IC is fully operational.
External Bootstrap Capacitor
Connect a 0.1μF low ESR ceramic capacitor between
BOOT and SW. This bootstrap capacitor provides the gate
driver supply voltage for the high side N-channel MOSFET
switch.
Over-Temperature Protection
The RT6217E includes an over-temperature protection
(OTP) circuitry to prevent overheating due to excessive
power dissipation. The OTP will shut down switching
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
operation when the junction temperature exceeds the OTP
threshold value. Once the junction temperature cools down
and is lower than the OTP lower threshold, the IC will
resume normal operation.
UVP Protection
The RT6217E detects under-voltage conditions by
monitoring
the feedback voltage on FB pin. When the
feedback voltage is lower than 50% of the target voltage,
the UVP comparator will go high to turn off both internal
high-side and low-side MOSFETs.
DS6217E-02 July 2016
www.richtek.com
3
RT6217E
Absolute Maximum Ratings
(Note 1)
Supply Input Voltage, VIN -----------------------------------------------------------------------------------------------
−0.3V
to 28V
Enable Pin Voltage, EN --------------------------------------------------------------------------------------------------
−0.3V
to 28V
Switch Voltage, SW -------------------------------------------------------------------------------------------------------
−0.3V
to 28V
SW (t
≤
10ns) --------------------------------------------------------------------------------------------------------------
−5V
to 30V
BOOT to SW, V
BOOT
−
V
SW ---------------------------------------------------------------------------------------------------------------------------------------
−0.3V
to 6V
BOOT Voltage --------------------------------------------------------------------------------------------------------------
−0.3V
to 34V
Other Pins -------------------------------------------------------------------------------------------------------------------
−0.3V
to 6V
Power Dissipation, P
D
@ T
A
= 25°C
TSOT-23-8 (FC) ------------------------------------------------------------------------------------------------------------- 1.428W
Package Thermal Resistance (Note 2)
TSOT-23-8 (FC),
θ
JA
------------------------------------------------------------------------------------------------------- 70°C/W
TSOT-23-8 (FC),
θ
JC
------------------------------------------------------------------------------------------------------- 15°C/W
Junction Temperature ----------------------------------------------------------------------------------------------------- 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 Input Voltage ------------------------------------------------------------------------------------------------------ 4.5V to 24V
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 Voltage
Symbol
Test Conditions
Min
4.5
Typ
--
3.9
350
Max
24
4.1
--
Unit
V
V
mV
VIN Supply Input Operating Voltage V
IN
VIN Under-Voltage Lockout
Threshold
VIN Under-Voltage Lockout
Threshold-Hysteresis
Supply Current
Supply Current (Shutdown)
Supply Current (Quiescent)
Soft-Start
Internal Soft-Start Period
Enable Voltage
EN Rising Threshold
EN Hysteresis
V
ENH
V
EN
t
SS
V
FB
from 0% to 100%
I
SHDN
I
Q
V
EN
= 0V
V
EN
= 2V, V
FB
= 1V,
V
MODE
= 0V (Not Switching)
V
UVLO
V
UVLO
V
IN
Rising
3.7
--
--
--
--
150
10
250
A
A
--
1.2
80
1500
1.4
150
--
1.6
220
s
V
mV
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS6217E-02 July 2016
RT6217E
Parameter
Mode Input Voltage
Mode Input High Voltage
Mode Input Low Voltage
Feedback Voltage
Feedback Voltage
Internal MOSFET
High-Side Switch-On Resistance
Low-Side Switch-On Resistance
Current Limit
Low-Side Switch Valley Current
Limit
Switching Frequency
Switching Frequency
On-Time Timer Control
Maximum Duty Cycle
Minimum On-Time
Thermal Shutdown
Thermal Shutdown
Thermal Hysteresis
Output Under Voltage Protections
UVP Trip Threshold
UVP detect
Hysteresis
--
--
50
10
--
--
%
%
T
SD
T
SD
--
--
160
25
--
--
C
C
D
MAX
t
ON
--
--
90
60
--
--
%
ns
f
SW
--
500
--
kHz
I
LIM_L
3.3
--
4.2
5.5
--
--
A
A
R
DS(ON)_H
R
DS(ON)_L
V
BOOT
V
SW
= 4.8V
--
--
85
40
--
--
m
m
V
FB
779
791
803
mV
V
MODEH
V
MODEL
2
--
--
--
--
0.4
V
V
Symbol
Test Conditions
Min
Typ
Max
Unit
High-Side Switch Peak Current Limit I
LIM_H
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 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.
DS6217E-02 July 2016
www.richtek.com
5
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