RT9728

RT9728
120mΩ
Ω, 1.3A Power Switch with Programmable Current Limit
General Description
Features
The RT9728 is a cost effective, low voltage, single
P-MOSFET high side power switch IC for USB application
with a programmable current limit feature. Low switch-on
resistance (typ.120mΩ) and low supply current (typ.
120μA) are realized in this IC.The RT9728 can offer a
programmable current limit threshold between 75mA and
1.3A (typ.) via an external resistor. The ±10% current limit
accuracy can be realized for all current limit settings.
Besides, 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 from happening due to high inrush current.
The RT9728 is an ideal solution for USB power supply
and can support flexible applications since it is functional
for various current limit requirements. It is available in
WDFN-6L 2x2 package.

Ordering Information
RT9728








±10% Current Limit Accuracy @ 1.3A
Adjustable Current Limit : 75mA to 1.3A (typ.)
Meets USB Current Limiting Requirements
Operating Voltage Range : 2.5V to 5.5V
Reverse Input − Output Voltage Protection
Built-in Soft-Start
120mΩ
Ω High Side MOSFET
120μ
μA Supply Current
RoHS Compliant and Halogen Free
Applications





USB Bus/Self Powered Hubs
USB Peripheral Ports
ACPI Power Distribution
Battery Power Equipment
3G/3.5G Data Card, Set-Top Boxes
Pin Configurations
Package Type
QW : WDFN-6L 2x2 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Z : ECO (Ecological Element with
Halogen Free and Pb free)
VOUT
1
ILIM
FAULT
2
GND
(TOP VIEW)
Pin 1 Orientation***
(2) : Quadrant 2, Follow EIA-481-D
(For RT9728GQW Only)
3
7
5
VIN
GND
4
EN
6
WDFN-6L 2x2
Marking Information
RT9728GQW
J0 : Product Code
Note :
***Empty means Pin1 orientation is Quadrant 1
J0W
W : Date code
Richtek products are :

RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.

RT9728ZQW
J0 : Product Code
Suitable for use in SnPb or Pb-free soldering processes.
J0W
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS9728-05
October 2014
W : Date Code
is a registered trademark of Richtek Technology Corporation.
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RT9728
Typical Application Circuit
6 VIN
VIN
CIN
10µF
RFAULT
100k
VOUT 1
RT9728
3 FAULT
4 EN
FAULT Signal
Chip Enable
ILIM 2
GND
VOUT
150µF
RILIM
5, 7 (Exposed Pad)
Function Block Diagram
Reverse Voltage
Comparator
+
Switch
well
-
Current
Sense
VIN
VOUT
4ms
Deglitch
EN
Drive
Current
Limit
FAULT
UVLO
Thermal
Sense
7.5ms
Deglitch
GND
ILIM
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
VOUT
Power Switch Output.
2
ILIM
External Resistor Used to Set Current Limit Threshold. Recommended 19.1k
 RILIM  232k.
3
FAULT
Active-Low Open-Drain Output. Asserted during over current, over temperature,
or reverse voltage conditions.
4
EN
Chip Enable (Active High).
5,
GND
7 (Exposed Pad)
6
VIN
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Supply Input Voltage.
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is a registered trademark of Richtek Technology Corporation.
DS9728-05
October 2014
RT9728
Absolute Maximum Ratings








(Note 1)
Supply Input Voltage -----------------------------------------------------------------------------------------------------Other Pin Voltage --------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C
WDFN-6L 2x2 -------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
WDFN-6L 2x2, θJA --------------------------------------------------------------------------------------------------------WDFN-6L 2x2, θJC -------------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3)
HBM (Human Body Model) ----------------------------------------------------------------------------------------------
Recommended Operating Conditions



−0.3V to 6V
−0.3V to 6V
0.606W
165°C/W
7°C/W
260°C
150°C
−65°C to 150°C
2kV
(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
(VIN = 3.6V, 19.1kΩ  RILIM  232kΩ, TA = 25°C, unless otherwise specified)
Parameter
EN Threshold
Voltage
Symbol
Test Conditions
Typ
Max
Unit
Logic-High
VIH
1.1
--
--
Logic- Low
VIL
--
--
0.66
19.1
--
232
VIN Rising
--
2.35
--
VIN Falling
--
2.10
--
--
1
3
RILIM = 20k
--
120
170
RILIM = 210k
--
120
170
--
1
3
A
--
160
--
°C
--
120
--
m
RILIM = 20k
1166
1295
1425
RILIM = 49.9k
468
520
572
RILIM = 210k
110
130
150
ILIM Shorted to VIN
50
75
100
--
135
--
Current-Limit Threshold
Resistor Range
RILIM
Under Voltage Lockout
Threshold
UVLO
Shutdown Current
ISHDN
VIN = 5.5V, No Load on VOUT , VEN = 0V
Quiescent Current
IQ
VIN = 5.5V, No
Load on VOUT
Reverse Leakage Current
IREV
VOUT = 5.5V, VIN = 0V
Thermal Shutdown
Temperature
Static Drain-Source
On-State Resistance
Current Limit
TSD
RDS(ON)
ILIM
ISW = 0.2A
Reverse Voltage Comparator
Trip Point (VOUT VIN)
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DS9728-05
Min
October 2014
V
k
V
A
A
mA
mV
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RT9728
Parameter
FAULT Output Low Voltage
Symbol
VOL
Test Conditions
IFAULT = 1mA
Min
Typ
Max
Unit
--
180
--
mV
A
FAULT Off State Leakage
VFAULT = 5.5V
--
1
--
5
7.5
10
FAULT Deglitch
FAULT assertion or de-assertion due to
over current condition
FAULT assertion or de-assertion due to
reverse voltage condition
2
ms
4
6
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. θJA is measured at TA = 25°C on a low effective thermal conductivity single-layer test board per JEDEC 51-3. θJC 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.
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is a registered trademark of Richtek Technology Corporation.
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RT9728
Typical Operating Characteristics
Supply Current vs. Temperature
FAULT Deglitch Timing vs. Temperature
150
FAULT Deglitch Timing (ms) 1
10
Supply Current (µA)
140
130
120
110
100
90
9
8
7
6
5
80
-50
-25
0
25
50
75
100
-50
125
-25
0
Temperature (C)
25
50
75
100
125
Temperature (C)
On-Resistance vs. Temperature
Current Limit vs. Temperature
150
1.6
1.5
130
Current Limit (A)
On-Resistance (m Ω )
140
VIN = 3.6V
120
110
100
VIN = 5V
90
80
1.4
1.3
1.2
70
RILIM = 20kΩ
60
1.1
-50
-25
0
25
50
75
100
125
-50
-25
0
Temperature (C)
1.4
2.8
1.3
1.2
Rising
1.0
0.9
Falling
0.7
0.6
100
125
2.6
2.4
Rising
2.2
2.0
Falling
1.8
1.6
1.4
1.2
0.5
1.0
-50
-25
0
25
50
75
100
Temperature (C)
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS9728-05
75
Under Voltage Lockout vs. Temperature
3.0
Under Voltage Lockout (V)
EN Threshold Voltage (V) 1
EN Threshold Voltage vs. Temperature
0.8
50
Temperature (C)
1.5
1.1
25
October 2014
125
-50
-25
0
25
50
75
100
125
Temperature (C)
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RT9728
Power On from EN
Power Off from EN
VEN
(5V/Div)
VIN = 5V, COUT = 150μF,
RILIM = 20kΩ,ROUT = 5 Ω
VEN
(5V/Div)
VOUT
(2V/Div)
VOUT
(2V/Div)
I IN
(1A/Div)
VIN = 5V, COUT = 150μF,
RILIM = 20kΩ, ROUT = 5 Ω
I IN
(1A/Div)
Time (500μs/Div)
Time (500μs/Div)
Current Limit
Current Limit
Full Load (5Ω) to Short Circuit
VIN = 5V, COUT = 150μF, RILIM = 20kΩ
VOUT
(2V/Div)
VOUT
(2V/Div)
FAULT
(5V/Div)
FAULT
(5V/Div)
I IN
(1A/Div)
I IN
(1A/Div)
Short Circuit to Full Load (5Ω)
VIN = 5V, COUT = 150μF,
RILIM = 20kΩ
Time (2.5ms/Div)
Time (2.5ms/Div)
Current Limit
Current Limit
No Load to Short Circuit
VIN = 5V, COUT = 150μF,
RILIM = 20kΩ
VOUT
(2V/Div)
VOUT
(2V/Div)
FAULT
(5V/Div)
FAULT
(5V/Div)
I IN
(1A/Div)
I IN
(1A/Div)
Time (2.5ms/Div)
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VIN = 12V, VOUT = 3.3V, IOUT = 2A
Short Circuit to No Load
VIN = 5V, COUT = 150μF,
RILIM = 20kΩ
Time (2.5ms/Div)
is a registered trademark of Richtek Technology Corporation.
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October 2014
RT9728
Static Drain-Source Current vs. VIN - VOUT
1400
1200
1000
800
600
400
200
VIN = 5.5V, RILIM = 20kΩ
0
160
140
120
100
80
60
40
20
VIN = 5.5V, RILIM = 200kΩ
0
0
200
400
600
800
VIN - VOUT (mV)
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DS9728-05
Static Drain-Source Current (mA)1
Static Drain-Source Current (mA)1
Static Drain-Source Current vs. VIN - VOUT
1600
October 2014
1000
0
200
400
600
800
1000
VIN - VOUT (mV)
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RT9728
Application Information
Current Limiting and Short Circuit Protection
When a heavy load or short circuit situation occurs while
the switch is enabled, large transient current may flow
through the device. The RT9728 includes a current limit
circuitry to prevent these large currents from damaging
the MOSFET switch and the hub downstream ports. The
RT9728 provides an adjustable current limit threshold
between 120mA and 1.3A (typ.) via an external resistor,
RILIM, between 19.1kΩ and 232kΩ. However, if the ILIM
pin is connected to VIN, the current limit threshold will be
75mA (typ.). Once the current limit threshold is exceeded,
the device enters constant current mode until either
thermal shutdown occurs or the fault is removed. The table1
shows a recommended current limit value vs. RILIM resistor.
Current Limit Threshold vs. RILIM
1600
Current Limit Threshold (mA)
The RT9728 is a single P-MOSFET high side power switch
with active high enable input, optimized for self powered
and bus powered Universal Serial Bus (USB) applications.
The switch's low R DS(ON) meets USB voltage drop
requirements and a flag output is available to indicate fault
conditions to the local USB controller.
1400
1200
1000
800
600
400
200
0
20
50
80
110
140
170
200
230
RILIM (k Ω )
Figure 1. Current Limit Threshold vs. RILIM
Table 1. Recommended RILIM Resistor Selections
Desired Nominal
Current Limit (mA)
75
Ideal Resistor
(k)
Closet 1%
Resistor (k)
Short Ilim to VIN
Actual Limits (Include R Tolerance)
IOS Min (mA)
IOS Nom (mA)
IOS Max (mA)
50.0
75.0
100.0
120
226.1
226.0
101.3
120.0
142.1
200
134.0
133.0
173.7
201.5
233.9
300
88.5
88.7
262.1
299.4
342.3
400
65.9
66.5
351.1
396.7
448.7
500
52.5
52.3
443.9
501.6
562.4
600
43.5
43.2
535.1
604.6
674.1
700
37.2
37.4
616.0
696.0
776.0
800
32.4
32.4
708.7
800.8
892.9
900
28.7
28.7
797.8
901.5
1005.2
1000
25.8
26.1
875.4
989.1
1102.8
1100
23.4
23.2
982.1
1109.7
1237.3
1200
21.4
21.5
1057.9
1195.4
1332.9
1300
19.7
19.6
1158.0
1308.5
1459.0
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RT9728
Fault Flag
The RT9728 provides a FAULT signal pin which is an NChannel open drain MOSFET output. This open drain
output goes low when current exceeds current limit
threshold. The FAULT output is capable of sinking a 1mA
load to typically 180mV above ground. The FAULT pin
requires a pull-up resistor ; this resistor should be large
in value to reduce energy drain. A 100kΩ pull-up resistor
works well for most applications. In case of an over current
condition, FAULT will be asserted only after the flag
response delay time, tD, has elapsed. This ensures that
FAULT is asserted upon valid over current conditions and
that erroneous error reporting is eliminated. For example,
false over current conditions may occur during hot-plug
events when extremely large capacitive loads are
connected, which induces a high transient inrush current
that exceeds the current limit threshold. The FAULT
response delay time, tD, is typically 7.5ms.
Supply Filter/Bypass Capacitor
A 10μF low-ESR ceramic capacitor connected from VIN to
GND and located close to the device is strongly
recommended to prevent input voltage drooping during hotplug events. However, higher capacitor values may be used
to further reduce the voltage droop on the input. Without
this bypass capacitor, an output short may cause sufficient
ringing on the input (from source lead inductance) to
destroy the internal control circuitry. Note that the input
transient voltage must never exceed 6V as stated in the
Absolute Maximum Ratings.
capacitor itself should have a low dissipation factor to allow
decoupling at higher frequencies.
Chip Enable Input
The RT9728 will be disabled when the EN pin is in a logic
low condition. During this condition, the internal circuitry
and MOSFET are turned off, reducing the supply current
to 1μA typical. The maximum guaranteed voltage for a
logic-low at the EN pin is 0.66V. A minimum guaranteed
voltage of 1.1V at the EN pin will turn off the RT9728.
Floating the input may cause unpredictable operation. EN
should not be allowed to go negative with respect to GND.
Under Voltage Lockout
Under Voltage Lockout (UVLO) prevents the MOSFET
switch from turning on until input voltage exceeds
approximately 2.3V. If input voltage drops below
approximately 2.1V, UVLO turns off the MOSFET switch
and FAULT will be asserted accordingly. The under voltage
lockout detection functions only when the switch is
enabled.
Thermal Considerations
For continuous operation, do not exceed absolute
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of the IC
package, PCB layout, rate of surrounding airflow, and
difference between junction and ambient temperature. The
maximum power dissipation can be calculated by the
following formula :
PD(MAX) = (TJ(MAX) − TA) / θJA
Output Filter Capacitor
A low-ESR 150μF aluminum electrolytic capacitor
connected between V OUT and GND is strongly
recommended to meet the USB standard maximum droop
requirement for the hub, VBUS. Standard bypass methods
should be used to minimize inductance and resistance
between the bypass capacitor and the downstream
connector to reduce EMI and decouple voltage droop
caused by hot-insertion transients in downstream cables.
Ferrite beads in series with VBUS, the ground line and the
0.1μF bypass capacitors at the power connector pins are
recommended for EMI and ESD protection. The bypass
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October 2014
where TJ(MAX) is the maximum junction temperature, TA is
the ambient temperature, and θJA is the junction to ambient
thermal resistance.
For recommended operating condition specifications, the
maximum junction temperature is 125°C. The junction to
ambient thermal resistance, θJA, is layout dependent. For
WDFN-6L 2x2 packages, the thermal resistance, θJA, is
165°C/W on a standard JEDEC 51-3 single layer thermal
test board. The maximum power dissipation at TA = 25°C
can be calculated by the following formula :
PD(MAX) = (125°C − 25°C) / (165°C/W) = 0.606W for
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RT9728
Maximum Power Dissipation (W)1
The maximum power dissipation depends on the operating
ambient temperature for fixed T J(MAX) and thermal
resistance, θJA. The derating curve in Figure 2 allows the
designer to see the effect of rising ambient temperature
on the maximum power dissipation.
0.65
Four-Layer PCB
0.60
0.55
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 2. Derating Curve of Maximum Power Dissipation
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RT9728
Outline Dimension
D2
D
L
E
E2
1
e
2
b
A
A1
SEE DETAIL A
A3
1
2
1
DETAIL A
Pin #1 ID and Tie Bar Mark Options
Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min
Max
Min
Max
A
0.700
0.800
0.028
0.031
A1
0.000
0.050
0.000
0.002
A3
0.175
0.250
0.007
0.010
b
0.200
0.350
0.008
0.014
D
1.950
2.050
0.077
0.081
D2
1.000
1.450
0.039
0.057
E
1.950
2.050
0.077
0.081
E2
0.500
0.850
0.020
0.033
e
L
0.650
0.300
0.026
0.400
0.012
0.016
W-Type 6L DFN 2x2 Package
Richtek Technology Corporation
14F, No. 8, Tai Yuen 1st Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789
Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should
obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot
assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be
accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third
parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries.
DS9728-05
October 2014
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