RT9728C

®
RT9728C
120mΩ
Ω, 1.3A Power Switch with Programmable Current Limit
General Description
Features
The RT9728C 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 RT9728C 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. 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 from happening due to high inrush current.
The RT9728C 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
SOT-23-6 and WDFN-6L 2x2 packages.

Ordering Information
RT9728C








±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
(TOP VIEW)
Package Type
E : SOT-23-6
QW : WDFN-6L 2x2
VOUT ILIM FAULT
6
Lead Plating System
G : Green (Halogen Free and Pb Free)
H : Chip Enable High
5
4
2
3
VIN GND EN
Note :
SOT-23-6

RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.

Suitable for use in SnPb or Pb-free soldering processes.
VOUT
1
ILIM
FAULT
2
GND
Richtek products are :
3
7
6
VIN
5
GND
EN
4
WDFN-6L 2x2
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RT9728C
Marking Information
RT9728CHGE
RT9728CHGQW
42= : Product Code
42=DNN
3W : Product Code
DNN : Date Code
3WW
W : Date Code
Typical Application Circuit
VIN
RFAULT
100k
CIN
10µF
FAULT Signal
Chip Enable
VIN
VOUT
RT9728C
FAULT
ILIM
EN
GND
VOUT
150µF
RILIM
Functional Pin Description
Pin No.
Pin Name
Pin Function
SOT-23-6
WDFN-6L 2x2
1
6
VIN
Input Voltage.
2
5,
7 (Exposed Pad)
GND
Ground. The exposed pad must be soldered to a large PCB and
connected to GND for maximum power dissipation.
3
4
EN
Chip Enable.
4
3
FAULT
Active-Low Open-Drain Output. Asserted during over current, over
temperature, or reverse-voltage conditions.
5
2
ILIM
Current Limit Set Pin. External resistor used to set current limit
threshold. Recommend 19.1k  RILIM  232k.
6
1
VOUT
Power Switch Output.
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RT9728C
Function Block Diagram
Switch
well
Reverse Voltage
Comparator
+
Current
Sense
VIN
VOUT
4ms
Deglitch
Drive
EN
≒60
Current
Limit
FAULT
UVLO
Thermal
Sense
7.5ms
Deglitch
GND
ILIM
Operation
The RT9728C are current-limited, power-distribution
switches using P-channel MOSFETs for applications
where short circuits or heavy capacitive loads will be
encountered. These devices allow the user to program
the current-limit threshold between 75mA and 1.3A (typ)
via an external resistor. Additional device shutdown features
include over temperature protection and reverse-voltage
protection.
The driver controls the gate voltage of the power switch.
The driver incorporates circuitry that controls the rise and
fall times of the output voltage to limit large current and
voltage surges and provides built-in soft-start functionality.
The RT9728C enters the constant-current mode when the
load exceeds the current-limit threshold.
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RT9728C
Absolute Maximum Ratings








(Note 1)
Supply Input Voltage -----------------------------------------------------------------------------------------------------Other Pin Voltage --------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C
SOT-23-6 -------------------------------------------------------------------------------------------------------------------WDFN-6L 2x2 -------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
SOT-23-6, θJA --------------------------------------------------------------------------------------------------------------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
0.4W
0.606W
250°C/W
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 Input Voltage
Symbol
Test Conditions
Min
Typ
Max
Logic-High VIH
1.1
--
--
Logic- Low VIL
--
--
0.66
19.1
--
232
VIN Rising
--
2.3
--
VIN Falling
--
2.1
--
--
1
3
RILIM = 20k
--
120
170
RILIM = 210k
--
120
170
--
1
3
A
--
160
--
°C
--
120
--
m
RILIM = 20k
1190
1295
1400
RILIM = 49.9k
468
520
572
RILIM = 210k
110
130
150
ILIM Shorted to VIN
50
75
100
Current Limit Threshold
Resistor Range
RILIM
Under Voltage Lockout
Threshold
VUVLO
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
Thermal Shutdown
Temperature
Static Drain-Source On-State
Resistance
IREV
VOUT = 5.5V, VIN = 0V
Current Limit
(nominal 1%) from ILIM to GND
TSD
RDS(ON)
ILIM
ISW = 0.2A
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Unit
V
k
V
A
A
mA
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RT9728C
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
--
135
--
mV
IFAULT = 1mA
--
180
--
mV
FAULT Off State Leakage
VFAULT = 5.5V
--
1
--
A
FAULT Deglitch
FAULT assertion or de-assertion due to
over current condition
5
7.5
10
FAULT assertion or de-assertion due to
reverse voltage condition
2
4
6
Reverse Voltage Comparator
Trip Point (VOUT VIN)
FAULT Output Low Voltage
VOL
ms
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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RT9728C
Typical Operating Characteristics
Supply Current vs. Temperature
Fault Deglitch Timing vs. Temperature
150
10
Fault Deglitch Timing (ms)
Supply Current (μA)
140
130
120
110
100
90
80
9
8
7
6
5
-50
-25
0
25
50
75
100
125
-50
-25
0
Temperature (°C)
25
50
75
100
125
Temperature (°C)
Current Limit vs. Temperature
On- Resistance vs. Temperature
1.6
150
1.5
130
120
Current Limit (A)
On-Resistance (mΩ )
140
VIN = 3.6V
110
100
90
VIN = 5V
80
1.4
1.3
1.2
70
RILIM = 20kΩ
1.1
60
-50
-25
0
25
50
75
100
-50
125
-25
0
1.4
2.8
Under Voltage Lockout (V)
EN Threshold Voltage (V) 1
3.0
1.3
1.2
Rising
1.0
0.9
0.8
50
75
100
125
Under Voltage Lockout vs. Temperature
EN Threshold Voltage vs. Temperature
1.5
1.1
25
Temperature (°C)
Temperature (°C)
Falling
0.7
0.6
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)
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125
-50
-25
0
25
50
75
100
125
Temperature (°C)
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RT9728C
Power On from EN
Power Off from EN
VEN
(10V/Div)
VEN
(10V/Div)
VOUT
(5V/Div)
VOUT
(5V/Div)
I IN
(1A/Div)
I IN
(1A/Div)
RT9728C, VIN = 5V, COUT = 150μF,
RILIM = 20kΩ, ROUT = 5Ω
RT9728C, VIN = 5V, COUT = 150μF,
RILIM = 20kΩ, ROUT = 5Ω
Time (500μs/Div)
Time (500μs/Div)
Current Limit
Current Limit
Full Load (5Ω) to Short Circuit
Short Circuit to Full Load (5Ω)
VOUT
(2V/Div)
Fault
(5V/Div)
VOUT
(2V/Div)
Fault
(5V/Div)
I IN
(1A/Div)
I IN
(1A/Div)
VIN = 5V, COUT = 150μF,
RILIM = 20kΩ
VIN = 5V, COUT = 150μF,
RILIM = 20kΩ
Time (2.5ms/Div)
Time (2.5ms/Div)
Current Limit
Current Limit
No Load to Short Circuit
Short Circuit to No Load
VIN = 5V, COUT = 150μF,
RILIM = 20kΩ
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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RT9728C
Static Drain-Source Current vs. VIN - VOUT
VIN = 5.5V, RILIM = 20kΩ
1400
1200
1000
800
600
400
200
0
0
200
400
600
800
VIN - VOUT (mV)
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1000
160
Static Drain-Source Current (mA)1
Static Drain-Source Current (mA)1
Static Drain-Source Current vs. VIN - VOUT
1600
VIN = 5.5V, RILIM = 200kΩ
140
120
100
80
60
40
20
0
0
200
400
600
800
1000
VIN - VOUT (mV)
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RT9728C
Applications 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 RT9728C includes a current-limit
circuitry to prevent these large currents from damaging
the MOSFET switch and the hub downstream ports. The
RT9728C 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 RT9728C is a single P-MOSFET high-side power
switch with active-high/low enable input, optimized for selfpowered and bus-powered Universal Serial Bus (USB)
applications. The switch's low RDS(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)
Ideal Resistor
(k)
75
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
1178.0
1308.5
1439.0
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RT9728C
Fault Flag
The RT9728C 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,
VOUT − VIN exceeds reverse voltage trip level, or the die
temperature exceeds 160°C approximately. 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.
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
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are recommended for EMI and ESD protection. The bypass
capacitor itself should have a low dissipation factor to allow
decoupling at higher frequencies.
Chip Enable Input
The RT9728C will be disabled when the EN pin is in a
logic-low/high 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
RT9728C. 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
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
SOT-23-6 packages, the thermal resistance, θJA, is 250°C/
W on a standard JEDEC 51-3 single-layer thermal test
board. For WDFN-6L 2x2 packages, the thermal
resistance, θJA, is 165°C/W on a standard JEDEC 51-3
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RT9728C
single-layer thermal test board. The maximum power
dissipation at TA = 25°C can be calculated by the following
formula :
P D(MAX) = (125°C − 25°C) / (250°C/W) = 0.4W for
SOT-23-6 package
PD(MAX) = (125°C − 25°C) / (165°C/W) = 0.606W for
WDFN-6L 2x2 package
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 curves in Figure 2 allow the
designer to see the effect of rising ambient temperature
on the maximum power dissipation.
0.65
0.60
0.55
0.50
Single-Layer PCB
WDFN-6L 2x2
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
SOT-23-6
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 2. Derating Curve of Maximum Power Dissipation
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RT9728C
Outline Dimension
H
D
L
C
B
b
A
A1
e
Symbol
Dimensions In Millimeters
Dimensions In Inches
Min
Max
Min
Max
A
0.889
1.295
0.031
0.051
A1
0.000
0.152
0.000
0.006
B
1.397
1.803
0.055
0.071
b
0.250
0.560
0.010
0.022
C
2.591
2.997
0.102
0.118
D
2.692
3.099
0.106
0.122
e
0.838
1.041
0.033
0.041
H
0.080
0.254
0.003
0.010
L
0.300
0.610
0.012
0.024
SOT-23-6 Surface Mount Package
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RT9728C
D2
D
L
E
E2
1
e
b
A
A1
SEE DETAIL A
2
1
2
1
A3
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.
Symbol
Dimensions In Millimeters
Dimensions In Inches
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.
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