RT9711A/B/C/D
80mΩ
Ω, 1.5A/0.6A High-Side Power Switches with Flag
General Description
Features
The RT9711A/B/C/D are cost-effective, low voltage, single
N-MOSFET high-side power switches, optimized for selfpowered and bus-powered Universal Serial Bus (USB)
applications. The RT9711 series are equipped with a
charge pump circuitry to drive the internal MOSFET switch.
The switch's low RDS(ON), 80mΩ, meets USB voltage drop
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Compliant to USB Specifications
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Built-In N-MOSFET
Ω (SOT-23-5 & TSOT-23-5) and
` Typical RDS(ON) : 80mΩ
90mΩ
Ω (SOP-8 & MSOP-8)
Output Can Be Forced Higher Than Input (Off-State)
Low Supply Current :
25μ
μA Typical at Switch On State
1μ
μA Typical at Switch Off State
Guaranteed 1.5A for RT9711A/B and 0.6A for
RT9711C/D Continuous Load Current
Wide Input Voltage Ranges : 2.5V to 5.5V
Open-Drain Fault Flag Output
Hot Plug-In Application (Soft-Start)
1.7V Typical Under-Voltage Lockout (UVLO)
Current Limiting Protection
Thermal Shutdown Protection
Reverse Current Flow Blocking (no body diode)
Smallest SOT-23-5 and TSOT-23-5 Packages
Minimizes Board Space
UL Approved−E219878
TUV IEC60950-1 : 2005 Certified
RoHS Compliant and 100% Lead (Pb)-Free
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requirements. A flag output is available to indicate fault
conditions to the local USB controller.
Additional features include soft-start to limit inrush current
during plug-in, thermal shutdown to prevent catastrophic
switch failure from high-current loads, under-voltage
lockout (UVLO) to ensure that the device remains off
unless there is a valid input voltage present, fault current
is limited to typically 2.5A for RT9711A/B in dual ports
and 1A for RT9711C/D in single port in accordance with
the USB power requirements, lower quiescent current as
25μA making this device ideal for portable battery-operated
equipment.
The RT9711 series are available in SOT-23-5, TSOT-23-5,
SOP-8 and MSOP-8 packages fitting different aspect of
broad applications.
Ordering Information
RT9711
Package Type
B : SOT-23-5
BG : SOT-23-5 (G-Type)
J5 : TSOT-23-5
S : SOP-8
F : MSOP-8
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
Note :
Output Current/EN Function
A : 1.5A/Active High
B : 1.5A/Active Low
C : 0.6A/Active High
D : 0.6A/Active Low
Richtek products are :
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RoHS compliant and compatible with the current require-
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Suitable for use in SnPb or Pb-free soldering processes.
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Applications
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USB Bus/Self Powered Hubs
USB Peripherals
ACPI Power Distribution
PC Card Hot Swap
Notebook, Motherboard PCs
Battery-Powered Equipment
Hot-Plug Power Supplies
Battery-Charger Circuits
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
ments of IPC/JEDEC J-STD-020.
DS9711A/B/C/D-03 April 2011
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1
RT9711A/B/C/D
Pin Configurations
(TOP VIEW)
VOUT
VIN
VIN
EN/EN
5
4
5
4
2
GND
3
2
FLG GND EN/EN
Over -Current
FLG
RT9711A/B/C/D
GND
10µF
+
VOUT
COUT
3
6
VOUT
EN/EN
4
5
FLG
SOP-8/MSOP-8
Pin Name Pin Function
USB Controller
Supply
Voltage 5V
EN/EN
VOUT
VIN
Functional Pin Description
Pull-Up Resistor (10K to 100K)
RT9711A/C
Chip Enable
7
SOT-23-5 (G-Type)
Typical Application Circuit
VIN
VOUT
2
VOUT GND NC
SOT-23-5/TSOT-23-5
CIN
1µF
3
8
VIN
VBUS
Power Input Voltage
VOUT
Output Voltage
GND
Ground
EN/EN
Chip Enable. Never let this pin floating.
(Active High for RT9711A/C, Active Low
D+
D-
150µF
for RT9711B/D)
GND
RT9711B/D
Chip Enable
Ferrite
Beads
VIN
FLG
Open-Drain Fault Flag Output
Data
Note: A low-ESR 150μF aluminum electrolytic or tantalum
between VOUT and GND is strongly recommended to meet
the 330mV maximum droop requirement in the hub VBUS.
(see Application Information Section for further details)
Function Block Diagram
VIN
EN/EN
Bias
UVLO
Oscillator
Charge
Pump
Thermal
Protection
Current
Limiting
Gate
Control
Output Voltage
Detection
VOUT
FLG
Delay
GND
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DS9711A/B/C/D-03 April 2011
RT9711A/B/C/D
Absolute Maximum Ratings
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(Note 1)
Supply Voltage --------------------------------------------------------------------------------------------------------- 6.5V
Chip Enable Input Voltage ------------------------------------------------------------------------------------------- −0.3V to 6.5V
Flag Voltage ------------------------------------------------------------------------------------------------------------ 6.5V
Power Dissipation, PD @ TA = 25°C
SOT-23-5, TSOT-23-5 ------------------------------------------------------------------------------------------------- 0.4W
SOP-8, MSOP-8 ------------------------------------------------------------------------------------------------------- 0.625W
Package Thermal Resistance (Note 2)
SOT-23-5, TSOT-23-5, θJA ------------------------------------------------------------------------------------------- 250°C/W
SOP-8, MSOP-8, θJA ------------------------------------------------------------------------------------------------- 160°C/W
Junction Temperature ------------------------------------------------------------------------------------------------- 150°C
Lead Temperature (Soldering, 10 sec.) --------------------------------------------------------------------------- 260°C
Storage Temperature Range ---------------------------------------------------------------------------------------- −65°C to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Mode) ------------------------------------------------------------------------------------------ 2kV
MM (Machine Mode) -------------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions
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(Note 4)
Supply Input Voltage -------------------------------------------------------------------------------------------------- 2.5V to 5.5V
Chip Enable Input Voltage ------------------------------------------------------------------------------------------- 0V to 5.5V
Junction Temperature Range ---------------------------------------------------------------------------------------- −40°C to 125°C
Ambient Temperature Range ---------------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VIN = 5V, CIN = COUT = 1μF, TA = 25°C, unless otherwise specified)
Parameter
Switch On
Resistance
(RT9711A/B)
Switch On
Resistance
(RT9711C/D)
Symbol
SOT-23-5, TSOT-23-5
SOP-8, MSOP-8
SOT-23-5, TSOT-23-5
Test Conditions
I OUT = 1A, VIN = 5V
RDS(ON)
I OUT = 0.5A, VIN = 5V
SOP-8, MSOP-8
Min
Typ
Max
--
80
100
--
90
110
--
80
100
--
90
110
Units
mΩ
mΩ
ISW_ON
switch on, RLOAD Open
--
25
45
ISW_OFF
switch off, RLOAD Open
--
0.1
1
Logic-Low Voltage
V IL
V IN = 2.5V to 5.5V
--
--
0.8
V
Logic-High Voltage
V IH
V IN = 2.5V to 5.5V
2.0
--
--
V
EN/EN Input Current
IEN/EN
V EN/EN = 0V to 5.5V
--
0.01
--
μA
Output Leakage Current
ILEA K
V EN = 0V, V EN = 5V, R LOAD = 0Ω
--
0.5
10
μA
Output Turn-On Rise Time
TON_RISE 10% to 90% of VO UT rising
--
400
--
us
1.6
2.5
3.2
A
0.7
1
1.4
A
Supply Current
EN/EN
Threshold
Current Limit
RT9711A/B
RT9711C/D
ILIM
Current Ramp (< 0.1A/ms) on
V OUT
μA
To be continued
DS9711A/B/C/D-03 April 2011
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RT9711A/B/C/D
Parameter
Test Conditions
Min
Typ
Max
Units
ISC_FB
VOUT = 0V, measured prior to
thermal shutdown
--
1
--
--
0.8
--
FLAG Output Resistance
RFLG
ISINK = 1mA
--
20
400
Ω
FLAG Off Current
IFLG_OFF VFLG = 5V
--
0.01
1
μA
5
12
20
ms
--
75
150
Ω
1.3
1.7
--
V
--
0.1
--
V
Short Circuit
Fold-Back Current
FLAG Delay Time
RT9711A/B
Symbol
RT9711C/D
(Note 5)
tD
From fault condition to FLG
assertion
A
Shutdown Pull-Low Resistance
RDS
Under-voltage Lockout
VUVLO
VE N = 0V, VEN = 5V
VIN increasing
Under-voltage Hysteresis
ΔVUVLO
VIN decreasing
Thermal Shutdown Protection
TSD
--
130
--
°C
Thermal Shutdown Hysteresis
ΔTSD
--
20
--
°C
Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for
stress ratings. 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 for extended
periods may remain possibility to affect device reliability.
Note 2. θJA is measured in the natural convection at TA = 25°C on a low effective thermal conductivity single layer test board of
JEDEC 51-3 thermal measurement standard.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Note 5. The FLAG delay time is input voltage dependent, see“ Typical Operating Characteristics” graph for further details.
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DS9711A/B/C/D-03 April 2011
RT9711A/B/C/D
Typical Operating Characteristics
Switch On Resistance vs. Temperature
Switch On Resistance vs. Temperature
0.25
Switch On Resistance (Ω)
Switch On Resistance (Ω)
0.25
0.2
0.15
0.1
0.05
SOP-8, VIN = 5V, ILOAD = 1.5A
CIN = 1uF/X7R, COUT = 10μF/X7R
0
-40
-20
0
20
40
0.2
0.15
0.1
0.05
0
60
80
100
SOT-23-5, VIN = 5V, ILOAD = 1.5A
CIN = 1μF/X7R, COUT = 10μF/X7R
-40
120
-20
0
20
Temperature (°C)
Supply Current (uA)
Switch on Resistance (mΩ)
80
60
2.5
3
3.5
30
25
20
15
10
SOT-23-5, RL = Open
CIN = COUT = 33μF/Electrolytic
5
SOT-23-5, ILOAD = 1.5A
CIN = COUT = 33μF/Electrolytic
2
0
4
4.5
5
2
5.5
2.5
3
Input Voltage (V)
3.5
4
4.5
5
5.5
Input Voltage (V)
Supply Current vs. Temperature
Current Limit vs. Input Voltage
30
2
25
1.8
Current Limit (A)
Supply Current (uA)
120
35
100
20
15
10
0
100
40
120
5
80
Supply Current vs. Input Voltage
Switch on Resistance vs. Input Voltage
20
60
Temperature (°C)
140
40
40
1.6
1.4
1.2
VIN = 5V, Switch On, RLOAD Open
CIN = COUT = 33μF/Electrolytic
-40
-20
0
20
40
60
Temperature (°C)
DS9711A/B/C/D-03 April 2011
1
80
100
120
RT9711A/B, VIN = VEN = 5V
CIN = 1μF/X7R, COUT = 10μF/X7R
2
2.5
3
3.5
4
4.5
5
5.5
Input Voltage (V)
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RT9711A/B/C/D
EN PinThreshold Voltage vs. Input Voltage
Current Limit vs. Temperature
2
EN Threshold Voltage (V)
2
Current Limit (A)
1.8
1.6
1.4
1.2
RT9711A/B, VIN = 5V
CIN = 1μF/X7R, COUT = 10μF/X7R
1
-40
-20
0
20
40
60
1.6
1.2
0.8
0.4
0
80
100
RT9711B, ILOAD = 100mA
CIN = COUT = 33μF/Electrolytic
2
120
2.5
3
Turn-Off Leakage Current (uA)
EN Pin Threshold Voltage (V)
4
2
1.6
1.2
0.8
RT9711B, VIN = 5V, ILOAD = 100mA
CIN = COUT = 33μF/Electrolytic
-40
-20
0
20
40
60
3.5
5
5.5
VIN = 5V, RLOAD = 0Ω
CIN = 33μF/Electrolytic
COUT = 1μF/X7R
3
2.5
2
1.5
1
0.5
0
80
100
-40
120
-20
0
Temperature (°C)
20
40
60
80
100
120
Temperature (°C)
Turn-Off Falling Time vs. Temperature
Turn-On Rising Time vs. Temperature
100
700
600
Turn-Off Falling Time (us)
Turn-On Rising Time (us)
4.5
Turn-Off Leakage Current vs. Temperature
EN Pin Threshold Voltage vs. Temperature
2.4
0
4
Input Voltage (V)
Temperature (°C)
0.4
3.5
500
400
300
200
100
0
VIN = 5V, RLOAD = 30Ω
CIN = 33μF/Electrolytic
COUT = 1μF/Electrolytic
-40
-20
0
20
60
40
20
0
40
60
Temperature (°C)
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80
80
100
120
VIN = 5V, RLOAD = 30Ω
CIN = 33μF/Electrolytic
COUT = 1μF/Electrolytic
-40
-20
0
20
40
60
80
100
120
Temperature (°C)
DS9711A/B/C/D-03 April 2011
RT9711A/B/C/D
Swith Off Supply Current vs. Temperature
UVLO Threshold vs. Temperature
2.4
0.8
2
0.6
UVLO Threshold (V)
Swith Off Supply Current (uA)
1
0.4
0.2
0
-0.2
-0.4
-0.6
-1
-40
-20
0
20
40
1.2
0.8
0.4
VIN = 5V, RLOAD = Open
CIN = COUT = 33μF/Electrolytic
-0.8
1.6
0
60
80
100
VIN Increasing, ILOAD = 15mA
CIN = COUT = 33μF/Electrolytic
-40
120
-20
0
20
40
60
80
100
120
Temperature (°C)
Temperature (°C)
Flag Delay Time vs. Temperature
FLAG Delay Time vs. Input Voltage
16
20
Flag Delay Time (ms)
FLAG Delay Time (ms)
15
16
12
8
4
14
13
12
11
10
RLOAD = 1Ω
CIN = COUT = 33μF/Electrolytic
0
2
2.5
3
3.5
4
9
8
7
4.5
5
RLOAD = 1Ω, VIN = 5V
CIN = COUT = 33μF/Electrolytic
-40
5.5
-20
0
20
40
60
80
100
Input Voltage(V)
Temperature (°C)
Flag Response with Ramped Load
Load Transient Response
120
4.8V
VLAG
(5V/Div)
VOUT
(5V/Div)
VOUT
(1V/Div)
IOUT
(1A/Div)
SOT-23-5, VIN = 5V
CIN = COUT = 33μF/Electrolytic
Time (2.5ms/Div)
DS9711A/B/C/D-03 April 2011
IOUT
(1A/Div)
1.5A
VIN = 5V, COUT = 1μF
CIN = 33μF/Electrolytic
RLOAD = 1kΩ to 2.2Ω
Time (1ms/Div)
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RT9711A/B/C/D
Turn On Response
VEN
(5V/Div)
Turn Off Response
VEN
(5V/Div)
VOUT
(5V/Div)
RT9711B, VIN = 5V
RLOAD = 30Ω
CIN = 33μF/Electrolytic
COUT = 1μF/Electrolytic
VOUT
(5V/Div)
RT9711B, VIN = 5V, RLOAD = 30Ω
CIN = 33μF/Electrolytic
COUT = 1μF/Electrolytic
Time (100μs/Div)
Time (100μs/Div)
UVLO at Rising
UVLO at Falling
VIN = 5V, RLOAD = 30Ω
COUT = 1μF
CIN = 33μF/Electrolytic
VIN
(1V/Div)
VIN
(1V/Div)
SOT-23-5, VIN = 5V,
RLOAD = 30Ω, COUT = 1μF
CIN = 33μF/Electrolytic
VOUT
(1V/Div)
VOUT
(1V/Div)
Time (2.5ms/Div)
Time (5ms/Div)
Flag Response during Short Circuit
Flag Response during Over Load
VIN = 5V, RLOAD = 0Ω
CIN = COUT = 33μF/Electrolytic
VIN = 5V, RLOAD = 2Ω
CIN = COUT = 33μF/Electrolytic
VEN
(5V/Div)
VOUT
(5V/Div)
VFLG
(5V/Div)
VFLG
(5V/Div)
IOUT
(1A/Div)
IOUT
(1A/Div)
Time (5ms/Div)
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Time (5ms/Div)
DS9711A/B/C/D-03 April 2011
RT9711A/B/C/D
Output Voltage vs. Output Current
Output Voltage vs. Output Current
5.0
5.0
4.6
TA = 25°C
4.2
3.8
3.4
TA = -45°C
3.0
TA = 85°C
2.6
2.2
1.8
1.4
1.0
0.6
TA = 85°C
4.2
Output Voltage (V)
Output Voltage (V)
4.6
3.8
3.4
TA = -45°C
3.0
2.6
TA = 25°C
2.2
1.8
1.4
1.0
RT9711A, VIN = 5V
0
0.2
0.4
0.6
0.6
0.8
1
1.2
1.4
1.6
1.8
RT9711C, VIN = 5V
0
2
0.2
Output Current (A)
2.1
1.6
Current Limit Threshold (A)
Current Limit Threshold (A)
1.7
TA = -45°C
TA = 25°C
1.8
1.7
TA = 85°C
1.6
1.5
RT9711A, VIN = 5V
2.5
3
3.5
DS9711A/B/C/D-03 April 2011
1.5
1.4
1.3
4
4.5
1
1.2
1.4
1.6
5
5.5
TA = 25°C
TA = -45°C
TA = 85°C
1.2
1.1
1
Input Voltage (V)
0.8
Current Limit Threshold vs. Input Voltage
Current Limit Threshold vs. Input Voltage
1.9
0.6
Output Current (A)
2.2
2.0
0.4
RT9711C, VIN = 5V
2.5
3
3.5
4
4.5
5
5.5
Input Voltage (V)
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RT9711A/B/C/D
Applications Information
The RT9711A/B/C/D are single N-MOSFET high-side
power switches with enable input, optimized for selfpowered and bus-powered Universal Serial Bus (USB)
applications. The RT9711 series are equipped with a
charge pump circuitry to drive the internal N-MOSFET
switch; the switch's low RDS(ON), 80mΩ, meets USB
voltage drop requirements; and a flag output is available
to indicate fault conditions to the local USB controller.
Input and Output
VIN (input) is the power source connection to the internal
circuitry and the drain of the MOSFET. VOUT (output) is
the source of the MOSFET. In a typical application, current
flows through the switch from VIN to VOUT toward the load.
If VOUT is greater than VIN, current will flow from VOUT to
VIN since the MOSFET is bidirectional when on.
Unlike a normal MOSFET, there is no a parasitic body
diode between drain and source of the MOSFET, the
RT9711A/B/C/D prevents reverse current flow if VOUT being
externally forced to a higher voltage than VIN when the
output disabled (VEN < 0.8V or VEN > 2V).
D
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S
D
Soft Start for Hot Plug-In Applications
In order to eliminate the upstream voltage droop caused
by the large inrush current during hot-plug events, the
“soft-start” feature effectively isolates the power source
from extremely large capacitive loads, satisfying the USB
voltage droop requirements.
Fault Flag
The RT9711 series provides a FLG signal pin which is an
N-Channel open drain MOSFET output. This open drain
output goes low when VOUT < VIN − 1V, current limit or the
die temperature exceeds 130°C approximately. The FLG
output is capable of sinking a 10mA load to typically 200mV
above ground. The FLG 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 the case of an over-current condition, FLG
will be asserted only after the flag response delay time,
tD, has elapsed. This ensures that FLG is asserted only
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 and causes a high transient inrush
current that exceeds the current limit threshold. The FLG
response delay time tD is typically 10ms.
Under-Voltage Lockout
G
G
Normal MOSFET
RT9711A/B/C/D
Chip Enable Input
The switch will be disabled when the EN/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 0.1μA typical. Floating the EN/EN may cause
unpredictable operation. EN should not be allowed to go
negative with respect to GND. The EN/EN pin may be
directly tied to VIN (GND) to keep the part on.
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Under-voltage lockout (UVLO) prevents the MOSFET
switch from turning on until input voltage exceeds
approximately 1.7V. If input voltage drops below
approximately 1.3V, UVLO turns off the MOSFET switch,
FLG will be asserted accordingly. Under-voltage detection
functions only when the switch is enabled.
Current Limiting and Short-Circuit Protection
The current limit circuitry prevents damage to the MOSFET
switch and the hub downstream port but can deliver load
current up to the current limit threshold of typically 2.5A
through the switch of RT9711A/B and 1A for RT9711C/D
respectively. When a heavy load or short circuit is applied
to an enabled switch, a large transient current may flow
until the current limit circuitry responds. Once this current
DS9711A/B/C/D-03 April 2011
RT9711A/B/C/D
Thermal Shutdown
Thermal shutdown is employed to protect the device from
damage if the die temperature exceeds approxi- mately
130°C. If enabled, the switch automatically restarts when
the die temperature falls 20°C. The output and FLG signal
will continue to cycle on and off until the device is disabled
or the fault is removed.
Power Dissipation
The junction temperature of the RT9711 series depend on
several factors such as the load, PCB layout, ambient
temperature and package type. The output pin of
RT9711A/B/C/D can deliver the current of up to 1.5A
(RT9711A/B), and 0.6A (RT9711C/D) respectively over the
full operating junction temperature range. However, the
maximum output current must be derated at higher
ambient temperature to ensure the junction temperature
does not exceed 100°C. With all possible conditions, the
junction temperature must be within the range specified
under operating conditions. Power dissipation can be
calculated based on the output current and the RDS(ON) of
switch as below.
PD = RDS(ON) x IOUT2
Although the devices are rated for 1.5A and 0.6A of output
current, but the application may limit the amount of output
current based on the total power dissipation and the
ambient temperature. The final operating junction
temperature for any set of conditions can be estimated
by the following thermal equation :
PD (MAX) = (TJ (MAX) - TA) / θJA
Where T J(MAX) is the maximum operation junction
temperature 125°C, TA is the ambient temperature and the
θJA is the junction to ambient thermal resistance.
The junction to ambient thermal resistance θJA is layout
dependent. For SOT-23-5 and TSOT-23-5 packages, the
thermal resistance θJA is 250°C/W on the standard JEDEC
51-3 single-layer thermal test board.
DS9711A/B/C/D-03 April 2011
And for SOP-8 and MSOP-8 packages, the thermal
resistance θ JA is 160°C/W. The maximum power
dissipation at TA = 25°C can be calculated by following
formula :
P D(MAX) = (125°C − 25°C) / 250°C/W = 0.4W for
SOT-23-5 and TSOT-23-5 packages
PD(MAX) = (125°C − 25°C) / 160°C/W = 0.625W for
SOP-8 and MSOP-8 packages
The maximum power dissipation depends on operating
ambient temperature for fixed T J(MAX) and thermal
resistance θJA. For RT9711A/B/C/D packages, the Figure
1 of derating curves allows the designer to see the effect
of rising ambient temperature on the maximum power
allowed.
0.7
Maximum Power Dissipation (W)
limit threshold is exceeded the device enters constant
current mode until the thermal shutdown occurs or the
fault is removed.
Single Layer PCB
0.6
SOP-8, MSOP-8
0.5
0.4
0.3
SOT-23-5, TSOT-23-5
0.2
0.1
0
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 1. Derating Curves for RT9711A/B/C/D Package
Universal Serial Bus (USB) & Power Distribution
The goal of USB is to be enabled device from different
vendors to interoperate in an open architecture. USB
features include ease of use for the end user, a wide range
of workloads and applications, robustness, synergy with
the PC industry, and low-cost implement- ation. Benefits
include self-identifying peripherals, dynamically attachable
and reconfigurable peripherals, multiple connections
(support for concurrent operation of many devices), support
for as many as 127 physical devices, and compatibility
with PC Plug-and-Play architecture.
The Universal Serial Bus connects USB devices with a
USB host: each USB system has one USB host. USB
devices are classified either as hubs, which provide
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11
RT9711A/B/C/D
additional attachment points to the USB, or as functions,
which provide capabilities to the system (for example, a
digital joystick). Hub devices are then classified as either
Bus-Power Hubs or Self-Powered Hubs.
A Bus-Powered Hub draws all of the power to any internal
functions and downstream ports from the USB connector
power pins. The hub may draw up to 500mA from the
upstream device. External ports in a Bus-Powered Hub
can supply up to 100mA per port, with a maximum of four
external ports.
Self-Powered Hub power for the internal functions and
downstream ports does not come from the USB, although
the USB interface may draw up to 100mA from its
upstream connect, to allow the interface to function when
the remainder of the hub is powered down. The hub must
be able to supply up to 500mA on all of its external
downstream ports. Please refer to Universal Serial
Specification Revision 2.0 for more details on designing
compliant USB hub and host systems.
Over-Current protection devices such as fuses and PTC
resistors (also called polyfuse or polyswitch) have slow
trip times, high on-resistance, and lack the necessary
circuitry for USB-required fault reporting.
The faster trip time of the RT9711A/B/C/D power
distribution allow designers to design hubs that can operate
through faults. The RT9711A/B/C/D have low on-resistance
and internal fault-reporting circuitry that help the designer
to meet voltage regulation and fault notification
requirements.
Because the devices are also power switches, the designer
of self-powered hubs has the flexibility to turn off power to
output ports. Unlike a normal MOSFET, the devices have
controlled rise and fall times to provide the needed inrush
current limiting required for the bus-powered hub power
switch.
Supply Filter/Bypass Capacitor
A 1μF low-ESR ceramic capacitor from VIN to GND,
located at the device is strongly recommended to prevent
the input voltage drooping during hot-plug events. However,
higher capacitor values will further reduce the voltage droop
on the input. Furthermore, without the bypass capacitor,
an output short may cause sufficient ringing on the input
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12
(from source lead inductance) to destroy the internal
control circuitry. The input transient must not exceed 6.5V
of the absolute maximum supply voltage even for a short
duration.
Output Filter Capacitor
A low-ESR 150μF aluminum electrolytic or tantalum
between VOUT and GND is strongly recommended to meet
the 330mV maximum droop requirement in the hub VBUS
(Per USB 2.0, output ports must have a minimum 120μF
of low-ESR bulk capacitance per hub). 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 when downstream cables are hot-insertion
transients. 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 capacitor itself should have a low
dissipation factor to allow decoupling at higher frequencies.
Voltage Drop
The USB specification states a minimum port-output
voltage in two locations on the bus, 4.75V out of a SelfPowered Hub port and 4.40V out of a Bus-Powered Hub
port. As with the Self-Powered Hub, all resistive voltage
drops for the Bus-Powered Hub must be accounted for to
guarantee voltage regulation (see Figure 7-47 of Universal
Serial Specification Revision 2.0 ).
The following calculation determines VOUT (MIN) for multiple ports (NPORTS) ganged together through one switch (if
using one switch per port, NPORTS is equal to 1) :
VOUT (MIN) = 4.75V − [ II x ( 4 x RCONN + 2 x RCABLE ) ] −
(0.1A x NPORTS x RSWITCH ) − VPCB
Where
RCONN = Resistance of connector contacts
(two contacts per connector)
RCABLE = Resistance of upstream cable wires
(one 5V and one GND)
RSWITCH = Resistance of power switch
(80mΩ typical for RT9711A/B/C/D)
DS9711A/B/C/D-03 April 2011
RT9711A/B/C/D
VPCB = PCB voltage drop
The USB specification defines the maximum resistance
per contact (RCONN) of the USB connector to be 30mΩ
and the drop across the PCB and switch to be 100mV.
This basically leaves two variables in the equation: the
resistance of the switch and the resistance of the cable.
If the hub consumes the maximum current (II) of 500mA,
the maximum resistance of the cable is 90mΩ.
The resistance of the switch is defined as follows :
RSWITCH = { 4.75V − 4.4V − [ 0.5A x ( 4 x 30mΩ + 2 x
90mΩ) ] − VPCB } ÷ ( 0.1A x NPORTS )
= (200mV − VPCB ) ÷ ( 0.1A x NPORTS )
If the voltage drop across the PCB is limited to 100mV,
the maximum resistance for the switch is 250mΩ for four
ports ganged together. The RT9711A/B/C/D, with its
maximum 100mΩ on-resistance over temperature, easily
meets this requirement.
Layout Considerations
For best performance of the RT9711 series, the following
guidelines muse be strictly followed :
` Input and output capacitors should be placed close to
the IC and connected to ground plane to reduce noise
coupling.
` The GND should be connected to a strong ground plane
for heat sink.
` Keep the main current traces as possible as short and
wide. The input and output capacitors should be
placed as close as possible to the IC.
V IN
V OUT
GND
V IN
FLG
GND
EN
Figure 2. PCB Layout Guide
DS9711A/B/C/D-03 April 2011
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13
RT9711A/B/C/D
Outline Dimension
H
D
L
B
C
b
A
A1
e
Symbol
Dimensions In Millimeters
Dimensions In Inches
Min
Max
Min
Max
A
0.889
1.295
0.035
0.051
A1
0.000
0.152
0.000
0.006
B
1.397
1.803
0.055
0.071
b
0.356
0.559
0.014
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-23-5 Surface Mount Package
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14
DS9711A/B/C/D-03 April 2011
RT9711A/B/C/D
H
D
L
B
C
b
A
A1
e
Symbol
Dimensions In Millimeters
Dimensions In Inches
Min
Max
Min
Max
A
0.700
1.000
0.028
0.039
A1
0.000
0.100
0.000
0.004
B
1.397
1.803
0.055
0.071
b
0.300
0.559
0.012
0.022
C
2.591
3.000
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
TSOT-23-5 Surface Mount Package
DS9711A/B/C/D-03 April 2011
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15
RT9711A/B/C/D
H
A
M
J
B
F
C
I
D
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min
Max
Min
Max
A
4.801
5.004
0.189
0.197
B
3.810
3.988
0.150
0.157
C
1.346
1.753
0.053
0.069
D
0.330
0.508
0.013
0.020
F
1.194
1.346
0.047
0.053
H
0.170
0.254
0.007
0.010
I
0.050
0.254
0.002
0.010
J
5.791
6.200
0.228
0.244
M
0.400
1.270
0.016
0.050
8-Lead SOP Plastic Package
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16
DS9711A/B/C/D-03 April 2011
RT9711A/B/C/D
D
L
E1
E
e
A2
A
A1
b
Symbol
Dimensions In Millimeters
Dimensions In Inches
Min
Max
Min
Max
A
0.810
1.100
0.032
0.043
A1
0.000
0.150
0.000
0.006
A2
0.750
0.950
0.030
0.037
b
0.220
0.380
0.009
0.015
D
2.900
3.100
0.114
0.122
e
0.650
0.026
E
4.800
5.000
0.189
0.197
E1
2.900
3.100
0.114
0.122
L
0.400
0.800
0.016
0.031
8-Lead MSOP Plastic Package
Richtek Technology Corporation
Richtek Technology Corporation
Headquarter
Taipei Office (Marketing)
5F, No. 20, Taiyuen Street, Chupei City
5F, No. 95, Minchiuan Road, Hsintien City
Hsinchu, Taiwan, R.O.C.
Taipei County, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
Tel: (8862)86672399 Fax: (8862)86672377
Email: [email protected]
Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit
design, specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be
guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek.
DS9711A/B/C/D-03 April 2011
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17