®
RT9728B
120mΩ, 1.8A Power Switch with Adjustable Current Limit
Ω
General Description
The RT9728B is a cost effective, low voltage, single
P-MOSFET power switch IC for USB application with a
adjustable current limit feature. Low switch-on resistance
(typ. 120mΩ) and low supply current (typ. 120μA) are
realized in this IC. The RT9728B can offer a adjustable
current limit threshold between 75mA and 1.8A (typ.) via
an external resistor. The
±10%
current limit accuracy can
be realized for all current limit settings. In addition, a flag
output is available to indicate fault conditions to the local
USB controller. Furthermore, the chip also integrates an
embedded delay function to prevent mis-operation due to
high inrush current. The RT9728B is an ideal solution for
USB power supplies and can support flexible applications
since it is suitable for various current limit requirements.
It is available in the SOT-23-6 and WDFN-6L 2x2 packages.
Features
±
10% Current Limit Accuracy @ 1.3A
Adjustable Current Limit : 75mA to 1.8A (typ.)
Meets USB Current Limiting Requirements
Operating Voltage Range : 2.5V to 5.5V
Reverse Input−Output Voltage Protection
−
Built-in Soft-Start
120mΩ P-MOSFET
Ω
120μA Supply Current
μ
RoHS Compliant and Halogen Free
Ordering Information
RT9728B
Package Type
E : SOT-23-6
QW : WDFN-6L 2x2
Lead Plating System
G : Green (Halogen Free and Pb Free)
H : Chip Enable High
L : Chip Enable Low
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.
Applications
USB Bus/Self Powered Hubs
USB Peripheral Ports
ACPI Power Distribution
Battery Power Equipment
3G/3.5G Data Card, Set-Top Boxes
Simplified Application Circuit
V
IN
R
FAULT
FAULT Signal
Enable
C
IN
VIN
VOUT
RT9728B
ILIM
GND
R
ILIM
V
OUT
FAULT
EN/EN
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS9728B-00 August 2013
www.richtek.com
11
RT9728B
Marking Information
RT9728BHGE
0K= : Product Code
RT9728BLGE
0J= : Product Code
DNN : Date Code
0K=DNN
0J=DNN
DNN : Date Code
RT9728BHGQW
1R : Product Code
RT9728BLGQW
1Q : Product Code
W : Date Code
1RW
1QW
W : Date Code
Pin Configurations
(TOP VIEW)
VOUT ILIM FAULT
GND
6
5
2
4
3
VOUT
ILIM
FAULT
1
2
3
6
5
4
VIN
GND
EN/EN
7
VIN GND EN/EN
SOT-23-6
WDFN-6L 2x2
Functional Pin Description
Pin No.
SOT-23-6
1
2
3
4
5
6
WDFN-6L 2x2
6
5,
7 (Exposed Pad)
4
3
2
1
Pin Name
VIN
GND
EN/EN
FAULT
ILIM
VOUT
Power Input.
Ground. The exposed pad must be soldered to a large PCB and
connected to GND for maximum power dissipation.
Enable Control Input.
Active-Low Open-Drain Output. Asserted during over-current,
over-temperature, or reverse-voltage conditions.
Current Limit Setting. Connect an external resistor to set current
limit threshold. 15kΩ
≤
R
ILIM
≤
232kΩ is recommended.
Power Switch Output.
Pin Function
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS9728B-00 August 2013
RT9728B
Function Block Diagram
Reverse Voltage
Comparator
+
Switch
well
VIN
-
Current
Sense
4ms
Deglitch
Current
Limit
VOUT
EN/EN
Drive
FAULT
UVLO
Thermal
Sense
7.5ms
Deglitch
GND
ILIM
Operation
The RT9728B is a current-limited power switch using
P-MOSFET for applications where short-circuit or heavy
capacitive loads will be encountered. These devices allow
users to adjust the current limit threshold between 75mA
and 1.8A (typ.) via an external resistor. Additional device
shutdown features include over-temperature protection and
reverse-voltage protection.
The RT9728B provides built-in soft-start function. The driver
controls the gate voltage of the power switch. The driver
incorporates circuitry that controls the rising time and
falling time of the output voltage to limit large inrush current
and voltage surges. The RT9728B enters constant-current
mode when the load exceeds the current limit threshold.
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS9728B-00 August 2013
www.richtek.com
3
RT9728B
Absolute Maximum Ratings
(Note 1)
Supply Input Voltage, VIN -----------------------------------------------------------------------------------------------
Other Pins -------------------------------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
SOT-23-6 --------------------------------------------------------------------------------------------------------------------
WDFN-6L 2x2 --------------------------------------------------------------------------------------------------------------
Package Thermal Resistance (Note 2)
SOT-23-6,
θ
JA
---------------------------------------------------------------------------------------------------------------
−
0.3V to 6V
−
0.3V to 6V
0.4W
0.606W
250°C/W
WDFN-6L 2x2,
θ
JA
--------------------------------------------------------------------------------------------------------- 165°C/W
WDFN-6L 2x2,
θ
JC
-------------------------------------------------------------------------------------------------------- 7°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
Recommended Operating Conditions
(Note 4)
Supply Input Voltage, VIN ----------------------------------------------------------------------------------------------- 2.5V to 5.5V
Junction Temperature Range --------------------------------------------------------------------------------------------
−40°C
to 125°C
Ambient Temperature Range --------------------------------------------------------------------------------------------
−40°C
to 85°C
Electrical Characteristics
(V
IN
= 3.6V, 15kΩ
≤
R
ILIM
≤
232kΩ, T
A
= 25°C, unless otherwise specified)
Parameter
EN Input Voltage
Symbol
Test Conditions
Min
1.1
--
Typ
--
--
--
2.3
2.1
1
120
120
1
160
120
1295
520
130
75
Max
--
0.66
232
--
--
3
170
170
10
--
--
1425
572
156
--
Unit
V
kΩ
V
μA
μA
μA
°C
mΩ
Logic-High V
IH
Logic-Low V
IL
R
ILIM
V
UVLO
I
SHDN
I
Q
I
REV
(nominal 1%) from I
LIM
to GND
V
IN
Rising
V
IN
Falling
V
IN
= 3.6V, No Load on V
OUT
, V
EN
= 0V
V
IN
= 5.5V,
No Load on V
OUT
V
OUT
= 5V, V
IN
= 0V
R
ILIM
= 20kΩ
R
ILIM
= 210kΩ
Current Limit Threshold
Resistor Range
Under-Voltage Lockout
Threshold
Shutdown Current
Quiescent Current
Reverse Leakage Current
15
--
--
--
--
--
--
--
Thermal Shutdown Threshold T
SD
Static Drain-Source On-State
R
DS(ON)
Resistance
I
SW
= 0.2A
R
ILIM
= 20kΩ
Current Limit
I
LIM
R
ILIM
= 49.9kΩ
R
ILIM
= 210kΩ
ILIM Shorted to VIN
--
1166
468
104
--
mA
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS9728B-00 August 2013
RT9728B
Parameter
Reverse Voltage Comparator
Trip Point (V
OUT
−
V
IN
)
FAULT Output Low Voltage
FAULT Off State Leakage
FAULT Deglitch
V
OL
I
FAULT
= 1mA
V
FAULT
= 5.5V
FAULT assertion or de-assertion due to
over-current condition
FAULT assertion or de-assertion due to
reverse-voltage condition
Symbol
Test Conditions
Min
--
--
--
5
2
Typ
135
180
1
7.5
4
Max
--
--
--
10
ms
6
Unit
mV
mV
μA
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 low effective thermal conductivity single-layer test board per JEDEC 51-3.
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
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS9728B-00 August 2013
www.richtek.com
5
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