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RT7237C
2A, 18V, 800kHz Synchronous Step-Down Converter
General Description
The RT7237C 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
RT7237C's current mode architecture and external
compensation allow the transient response to be
optimized over a wide input range and loads. Cycle-by-
cycle current limit provides protection against shorted
outputs, and soft-start eliminates input current surge during
start-up. The RT7237C also provides under voltage
protection and thermal shutdown protection. The low
current (<3µA) shutdown mode provides output
disconnection, enabling easy power management in
battery-powered systems. The RT7237C is available in
an SOP-8 (Exposed Pad) package.
Features
±
1.5% High Accuracy Reference Voltage
4.5V to 18V Input Voltage Range
2A Output Current
Integrated N-MOSFET Switches
Current Mode Control
Fixed Frequency Operation : 800kHz
Output Adjustable from 0.8V to 12V
Stable with Low ESR Ceramic Output Capacitors
Up to 95% Efficiency
Programmable Soft-Start
Cycle-by-Cycle Over Current Limit
Input Under Voltage Lockout
Output Under Voltage Protection
Thermal Shutdown Protection
RoHS Compliant and Halogen Free
Marking Information
RT7253CHGSP : Product Number
Applications
Wireless AP/Router
Set-Top-Box
Industrial and Commercial Low Power Systems
LCD Monitors and TVs
Green Electronics/Appliances
Point of Load Regulation of High-Performance DSPs
RT7237CH
GSPYMDNN
YMDNN : Date Code
Simplified Application Circuit
V
IN
C
IN
Chip Enable
EN
SS
C
SS
GND
COMP
FB
C
C
R
C
R2
VIN
BOOT
RT7237C
SW
R1
C
OUT
C
BOOT
L
V
OUT
C
P
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7237C-07
February 2018
www.richtek.com
1
RT7237C
Ordering Information
RT7237C
Package Type
SP : SOP-8 (Exposed Pad-Option 2)
Lead Plating System
G : Green (Halogen Free and Pb Free)
H : UVP Hiccup
Note :
Richtek products are :
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
VIN
SW
GND
2
3
4
Pin Configurations
(TOP VIEW)
8
7
SS
EN
COMP
FB
GND
9
6
5
SOP-8 (Exposed Pad)
Functional Pin Description
Pin No.
1
2
3
4,
9 (Exposed Pad)
5
Pin Name
BOOT
VIN
SW
GND
FB
Pin Function
Bootstrap for High Side Gate Driver. Connect a 0.1µF or greater ceramic
capacitor from BOOT to SW pins.
Power Input. The Input Voltage range is from 4.5V to 18V. Must bypass with a
suitable large ceramic capacitor.
Switch Node. Connect this pin to an external L-C filter.
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Feedback Input. It is used to regulate the output of the converter to a set value
via an external resistive voltage divider.
Compensation Node. COMP is used to compensate the regulation control
loop. Connect a series RC network from COMP to GND. In some cases, an
additional capacitor from COMP to GND is required.
Enable Input. A logic high enables the converter; a logic low forces the IC into
shutdown mode reducing the supply current to less than 3µA.
Soft-Start Control Input. SS controls the soft-start period. Connect a capacitor
from SS to GND to set the soft-start period. A 0.1µF capacitor sets the
soft-start period to 13.5ms.
6
7
8
COMP
EN
SS
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS7237C-07
February 2018
RT7237C
Function Block Diagram
VIN
Internal
Regulator
Shutdown V V
A
CC
Comparator
1.2V
+
-
Lockout
Comparator
-
1.8V
+
V
CC
6µA
SS
0.8V
+
+EA
-
0.4V
Oscillator
Foldback
Control
+
-
UV
Comparator
Current Sense
Amplifier
Slope Comp
+
-
R
SENSE
V
A
BOOT
S
+
R
-
Current
Comparator
Q
Q
150mΩ
5kΩ
EN
SW
130mΩ
GND
FB
COMP
Operation
Internal Regulator
Provide internal power for logic control and switch gate
drivers.
Shutdown Comparator
Activate internal regulator once EN input level is higher
than the target level. Force IC to enter shutdown mode
when the EN input level is lower than 0.4V.
Lockout Comparator
Activate the current comparator, release lock-out logic,
and enable the switches as EN input level is higher than
lockout threshold voltage. Otherwise, the switches still
lock out.
Oscillator
The oscillator provides internal clock and controls the
converter's switching frequency.
Foldback Control
Dynamically adjust the internal clock. It provides a slower
frequency as a lower FB voltage.
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
UV Comparator
As FB voltage is lower than the UV voltage, it will activate
a UV protect scheme.
Error Amplifier
The output voltage COMP of the error amplifier is adjusted
by comparing FB signal with the internal reference voltage
and SS signal.
Current Sense Amplifier
R
SENSE
detects the peak current of the high side switch.
This signal is amplified by the current sense amplifier and
added with a slope compensation signal. Then, It controls
the switches by comparing this signal with the COMP
voltage.
DS7237C-07
February 2018
www.richtek.com
3
RT7237C
Absolute Maximum Ratings
(Note 1)
−0.3V
to 20V
−0.3V
to (V
IN
+ 0.3V)
−0.3V
to 6V
−0.3V
to 20V
Supply Input Voltage, VIN -----------------------------------------------------------------------------------------
Switch Voltage, SW ------------------------------------------------------------------------------------------------
V
BOOT
−
V
SW
----------------------------------------------------------------------------------------------------------
Other Pins Voltage -------------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
SOP-8 (Exposed Pad) --------------------------------------------------------------------------------------------- 1.333W
Package Thermal Resistance (Note 2)
SOP-8 (Exposed Pad),
θ
JA
---------------------------------------------------------------------------------------- 75°C/W
SOP-8 (Exposed Pad),
θ
JC
---------------------------------------------------------------------------------------
Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------
Junction Temperature -----------------------------------------------------------------------------------------------
Storage Temperature Range --------------------------------------------------------------------------------------
15°C/W
260°C
150°C
−65°C
to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Model) ---------------------------------------------------------------------------------------- 2kV
Recommended Operating Conditions
(Note 4)
Supply Input 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
Shutdown Supply Current
Supply Current
Reference Voltage
Error Amplifier
Transconductance
High Side Switch
On-Resistance
Low Side Switch
On-Resistance
High Side Switch Leakage
Current
Upper Switch Current Limit
COMP to Current Sense
Transconductance
Oscillation Frequency
Short Circuit Oscillation
Frequency
Maximum Duty Cycle
Symbol
V
EN
= 0V
Test Conditions
Min
--
--
0.788
--
--
--
Typ
0.5
0.8
0.8
940
150
130
0
4
3.7
800
270
84
Max
3
1.2
0.812
--
--
--
10
--
--
--
--
--
Unit
µA
mA
V
µA/V
mΩ
mΩ
µA
A
A/V
kHz
kHz
%
V
EN
= 3V, V
FB
= 0.9V
V
REF
G
EA
R
DS(ON)1
R
DS(ON)2
V
EN
= 0V, V
SW
= 0V
Min. Duty Cycle, V
BOOT
−
V
SW
= 4.8V
G
CS
f
OSC1
f
OSC2
D
MAX
V
FB
= 0V
V
FB
= 0.7V
4.5V
≤
V
IN
≤
18V
∆I
C
= ±10µA
--
--
--
--
--
--
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS7237C-07
February 2018
RT7237C
Parameter
Minimum On-Time
EN Input Threshold Logic-High
Voltage
Logic-Low
Input Under Voltage Lockout
Threshold
Input Under Voltage Lockout
Hysteresis
Soft-Start Current
Soft-Start Period
Thermal Shutdown
Symbol
t
ON
V
IH
V
IL
V
UVLO
∆V
UVLO
I
SS
t
SS
T
SD
V
SS
= 0V
C
SS
= 0.1µF
V
IN
Rising
Test Conditions
Min
--
2
--
3.8
--
--
--
--
Typ
100
--
--
4.2
320
6
13.5
150
Max
--
18
0.4
4.5
--
--
--
--
Unit
ns
V
V
mV
µA
ms
°C
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
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7237C-07
February 2018
www.richtek.com
5
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