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RT7231/32/33/34
4A, 18V, 650kHz, ACOT
TM
Synchronous Step-Down Converter
General Description
The RT7231/32/33/34 is a synchronous step-down DC/
DC converter with Advanced Constant On-Time (ACOT
TM
)
mode control. It achieves high power density to deliver up
to 4A output current from a 4.5V to 18V input supply. The
proprietary ACOT
TM
mode offers an optimal transient
response over a wide range of loads and all kinds of ceramic
capacitors, which allows the device to adopt very low ESR
output capacitor for ensuring performance stabilization. In
addition, RT7231/32/33/34 keeps an excellent constant
switching frequency under line and load variation and the
integrated synchronous power switches with the ACOT
TM
mode operation provides high efficiency in whole output
current load range. Cycle-by-cycle current limit provides
an accurate protection by a valley detection of low side
MOSFET and external soft-start setting eliminates input
current surge during startup. Protection functions include
thermal shutdown for RT7231/32/33/34, output Under
Voltage Protection (UVP) / Over Voltage Protection (OVP)
for RT7231/32. When the UVP/OVP is triggered, the device
will enter latch mode for TSSOP-14 (Exposed Pad), and
hiccup mode for WDFN-10L 3x3.
The RT7231/32 are available in TSSOP-14 (Exposed Pad)
and WDFN-10L 3x3 packages, and the RT7231 is operated
in forced continuous conduction mode.
The RT7233/34 are available in the SOP-8 (Exposed Pad)
package, and the RT7233 is operated in forced continuous
conduction mode.
Features
ACOT
TM
Mode Enables Fast Transient Response
4.5V to 18V Input Voltage Range
4A Output Current
50mΩ Internal Low Site N-MOSFET
Ω
Advanced Constant On-Time Control
Support All Ceramic Capacitors
Up to 95% Efficiency
650kHz Switching Frequency at all Load Current
(RT7231, RT7233)
Discontinuous Operating Mode at Light Load
(RT7232, RT7234)
Adjustable Output Voltage from 0.765V to 8V
Adjustable Soft-Start
Cycle-by-Cycle Current Limit
Input Under Voltage Lockout
Thermal Shutdown
RoHS Compliant and Halogen Free
Applications
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
RT7231/32/33/34
V
IN
VIN
VCC*
Enable
Power GOOD
EN
PGOOD*
VREG5
SS
GND*
SW
BOOT
FB
PGND
VS*
V
OUT
* : VCC pin for TSSOP-14 (Exposed Pad) only.
VS pin for TSSOP-14 (Exposed Pad) only.
GND pin for TSSOP-14 (Exposed Pad) only.
PGOOD pin for TSSOP-14 (Exposed Pad) and WDFN-10L 3x3 only.
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7231/32/33/34-10
February 2018
www.richtek.com
1
RT7231/32/33/34
Ordering Information
Continuous Switching Mode
Marking Information
RT7231GCP
RT7231GCP : Product Number
RT7231
Package Type
CP : TSSOP-14 (Exposed Pad)
QW : WDFN-10L 3x3 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
RT7233
Package Type
SP : SOP-8 (Exposed Pad-Option 2)
Lead Plating System
G : Green (Halogen Free and Pb Free)
RT7231GCP
YMDNN
YMDNN : Date Code
RT7231GQW
1Q= : Product Code
1Q=YM
DNN
YMDNN : Date Code
RT7233GSP
RT7233GSP : Product Number
RT7233
GSPYMDNN
YMDNN : Date Code
Discontinuous Operating Mode
RT7232
Package Type
CP : TSSOP-14 (Exposed Pad)
QW : WDFN-10L 3x3 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
RT7232GCP
RT7232GCP : Product Number
RT7232GCP
YMDNN
YMDNN : Date Code
RT7232GQW
RT7234
Package Type
SP : SOP-8 (Exposed Pad-Option 2)
Lead Plating System
G : Green (Halogen Free and Pb Free)
RT7234GSP
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.
1P= : Product Code
1P=YM
DNN
YMDNN : Date Code
RT7234GSP : Product Number
RT7234
GSPYMDNN
YMDNN : Date Code
Pin Configurations
(TOP VIEW)
VS
FB
VREG5
SS
GND
PGOOD
EN
14
2
3
4
5
6
7
15
13
12
PGND
PGND
11
10
9
8
TSSOP-14 (Exposed Pad)
WDFN-10L 3x3
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
www.richtek.com
2
9
VCC
VIN
BOOT
SW
SW
PGND
PGND
EN
FB
VREG5
SS
PGOOD
1
2
3
4
5
11
10
9
8
7
VIN
VIN
BOOT
SW
SW
EN
FB
VREG5
SS
2
3
4
8
VIN
BOOT
SW
PGND
PGND
9
7
6
5
SOP-8 (Exposed Pad)
is a registered trademark of Richtek Technology Corporation.
DS7231/32/33/34-10
February 2018
RT7231/32/33/34
Functional Pin Description
Pin No.
Pin Name
TSSOP-14
SOP-8
WDFN-10L 3x3
(Exposed Pad)
(Exposed Pad)
1
--
--
VS
Pin Function
Output Voltage Sense Input.
Feedback Voltage Input. It is used to regulate the
output of the converter to a set value via an external
resistive voltage divider. The feedback threshold
voltage is 0.765V typically.
Internal Regulator Output. Connect a 1µF capacitor
to GND to stabilize output voltage.
Soft-Start Time Setting. Connect an external capacitor
between this pin and GND to set the soft- start time.
Analog Ground.
Open Drain Power Good Indicator Output.
Enable Control Input. A logic-high enables the
converter; a logic-low forces the IC into shutdown
mode reducing the supply current to less than 10µA.
Power Ground. The exposed pad must be soldered
to a large PCB and connected to PGND for
maximum power dissipation.
Switch Node. Connect this pin to an external L-C
filter.
Bootstrap Supply for High Side Gate Driver. Connect
a 0.1µF capacitor between the BOOT and SW pin.
Power Input. The input voltage range is from 4.5V to
18V. Must bypass with a suitably large (
≥10µF
x 2)
ceramic capacitor.
Supply Voltage Input for Internal Linear Regulator to
the Control Circuitry.
2
2
2
FB
3
4
5
6
7
3
4
--
5
1
3
4
--
--
1
VREG5
SS
GND
PGOOD
EN
8, 9, 15
11
5, 9
PGND
(Exposed pad) (Exposed pad) (Exposed Pad)
10, 11
12
6, 7
8
6
7
SW
BOOT
13
14
9, 10
--
8
--
VIN
VCC
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7231/32/33/34-10
February 2018
www.richtek.com
3
RT7231/32/33/34
Function Block Diagram
VCC*
VREG5
BOOT
EN
POR &
Reg
VBIAS
OC
UV & OV
SW
V
REG5
6µA
Ripple
Gen.
V
REF
Min.
Off-Time
VREG5
VIN
Control
Driver
SW
PGND
ZC
GND*
SS
V
IN
FB
VS*
On-Time
FB
+
-
-
Comparator
FB
0.9 x V
REF
Comparator
-
+
PGOOD*
* : VCC pin for TSSOP-14 (Exposed Pad) only.
GND pin for TSSOP-14 (Exposed Pad) only.
VS pin for TSSOP-14 (Exposed Pad) only.
PGOOD pin for TSSOP-14 (Exposed Pad) and WDFN-10L 3x3 only.
Operation
The RT7231/32/33/34 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.
Power Good
(for TSSOP-14 (Exposed Pad) and WDFN-10L 3x3 only)
After soft-start is finished, the power good function will be
activated. When the FB is activated, the PGOOD will
become an open-drain output. If the FB is below, the
PGOOD pin will be pulled low.
Internal Regulator
The regulator provides 5V power to supply the internal
control circuit. Connecting a 1µF ceramic capacitor for
decoupling and stability is required.
Soft-Start
In order to prevent the converter output voltage from
overshooting during the startup period, the soft-start
function is necessary. The soft-start time is adjustable
and can be set by an external capacitor.
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
Current Protection
The inductor current is monitored via the internal switches
in cycle-by-cycle. Once the output voltage drops under
UV threshold, the device will enter latch mode for TSSOP-
14 (Exposed Pad), and hiccup mode for WDFN-10L 3x3.
UVLO Protection
To protect the chip from operating at insufficient supply
voltage, the UVLO is needed. When the input voltage of
VCC is lower than the UVLO falling threshold voltage, the
device will be latch-off.
Output Discharge Control
(for TSSOP-14 (Exposed Pad) only)
When EN pin is low, the RT7231/32 will discharge the
output with an internal 50Ω MOSFET connected between
V
OUT
to GND pin.
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
automatically resume switching
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS7231/32/33/34-10
February 2018
RT7231/32/33/34
Absolute Maximum Ratings
(Note 1)
−0.3V
to 20V
−0.8V
to (V
IN
+ 0.3V)
−5V
to 25V
−0.3V
to 6V
−0.3V
to 20V
Supply Voltage, VIN, VCC ---------------------------------------------------------------------------------------
Switch Voltage, SW -----------------------------------------------------------------------------------------------
< 10ns ----------------------------------------------------------------------------------------------------------------
BOOT to SW --------------------------------------------------------------------------------------------------------
EN ----------------------------------------------------------------------------------------------------------------------
Other Pins ------------------------------------------------------------------------------------------------------------
−0.3V
to 6V
Power Dissipation, P
D
@ T
A
= 25°C
TSSOP-14 (Exposed Pad) --------------------------------------------------------------------------------------- 2.50W
WDFN-10L 3x3 ------------------------------------------------------------------------------------------------------ 1.67W
SOP-8 (Exposed Pad) -------------------------------------------------------------------------------------------- 2.174W
Package Thermal Resistance (Note 2)
TSSOP-14 (Exposed Pad),
θ
JA
--------------------------------------------------------------------------------- 40°C/W
WDFN-10L 3x3,
θ
JA
------------------------------------------------------------------------------------------------
WDFN-10L 3x3,
θ
JC
------------------------------------------------------------------------------------------------
SOP-8 (Exposed Pad),
θ
JA
---------------------------------------------------------------------------------------
SOP-8 (Exposed Pad),
θ
JC
--------------------------------------------------------------------------------------
60°C/W
7.5°C/W
46°C/W
7°C/W
Junction Temperature Range ------------------------------------------------------------------------------------- 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) ---------------------------------------------------------------------------------------- 3kV
MM (Machine Model) ----------------------------------------------------------------------------------------------- 250V
Recommended Operating Conditions
(Note 4)
Supply 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
Supply Current
Shutdown Current
Quiescent Current
Logic Threshold
EN Input Voltage
Logic-High
Logic-Low
Symbol
I
SHDN
I
Q
V
EN
= 0V
Test Conditions
Min
--
--
1.25
--
Typ
1
1
--
--
Max
10
1.3
18
0.85
Unit
µA
mA
V
EN
= 5V, V
FB
= 0.8V
V
V
FB
Voltage and Discharge Resistance
Feedback Threshold Voltage
Feedback Input Current
VOUT Discharge Resistance
V
FB
I
FB
R
DIS
T
A
= 25°C
T
A
=
−40°C
to 85°C
V
FB
= 0.8V
V
EN
= 0V, V
S
= 0.5V
0.757 0.765 0.773
0.755
--
--
--
0.01
50
0.775
0.1
100
V
µA
Ω
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7231/32/33/34-10
February 2018
www.richtek.com
5
意法半导体-低功耗射频
