RT9706PB [RICHTEK]
80mヘ, 500mA High-Side Power Switch with Flag; 80mΩ ， 500毫安高侧电源开关与国旗
| 型号： | RT9706PB |
| 厂家： | 
RICHTEK TECHNOLOGY CORPORATION |
| 描述： | 80mヘ, 500mA High-Side Power Switch with Flag |
| 文件： | 总14页 (文件大小：296K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
RT9706
80mΩ, 500mA High-Side Power Switch with Flag
General Description
Features
z Compliant to USB Specifications
The RT9706 is a cost-effective, low voltage, single
N-Channel MOSFET high-side power switch, optimized
for self-powered and bus-powered Universal Serial Bus
(USB) applications. The RT9706 equipped with a charge
pump circuitry to drive the internal 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.
z Built-In (Typically 80mΩ) N-Channel MOSFET
z Output Can Be Forced Higher than Input (Off-State)
z Low Supply Current :
`25μA Typical at Switch On State
`0.1μA Typical at Switch Off State
z Guaranteed 500mA Continuous Load Current
z Wide Input Voltage Ranges : 2V to 5.5V
z Open-Drain Fault Flag Output
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, lower
quiescent current as 25μA making this device ideal for
portable battery operated equipment.
z Hot Plug-In Application (Soft-Start)
z 1.7V Typical Under-Voltage Lockout (UVLO)
z Current Limiting Protection
z Thermal Shutdown Protection
z Reverse Current Flow Blocking (no body diode)
z Smallest SOT-23-5 Package Minimizes Board Space
z UL Approved−E219878
The RT9706 is available in SOT-23-5 package requiring
minimum board space and smallest components.
z RoHS Compliant and 100% Lead (Pb)-Free
Applications
z USB Bus/Self Powered Hubs
Ordering Information
RT9706
z USB Peripherals
Package Type
B : SOT-23-5
z ACPI PowerDistribution
z PC Card Hot Swap
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with Commer-
cial Standard)
z Notebook, Motherboard PCs
z Battery-Powered Equipment
z Hot-Plug Power Supplies
z Battery-Charger Circuits
Note :
RichTek Pb-free and Gree products are :
`RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
Pin Configurations
`Suitable for use in SnPb or Pb-free soldering processes.
`100% matte tin (Sn) plating.
(TOP VIEW)
EN
VOUT
VIN
1
2
3
5
Marking Information
GND
For marking information, contact our sales representative
directly or through a RichTek distributor located in your
area, otherwise visit our website for detail.
FLG
4
SOT-23-5
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1
RT9706
Typical Application Circuit
Pull-Up Resistor (10K to 100k)
USB Controller
Over -Current
Supply Voltage 5V
1uF
VIN
FLG
RT9706
VOUT
GND
V
OFF
ON
BUS
EN
D+
10uF
150uF
D-
GND
Ferrite
Beades
Data
Note:Alow-ESR 150μF aluminum electrolytic or tantalum between VOUT andGND is strongly recommended to meet
the 330mV maximum droop requirement in the hub VBUS. (see Application Information Section for further details)
Functional Pin Description
Pin Name
VIN
Pin Function
Power Input Voltage
Output Voltage
VOUT
GND
EN
Ground
Chip Enable (Active Low)
Open-Drain Fault Flag Output
FLG
Function Block Diagram
VIN
Bias
EN
Current
Limiting
UVLO
Gate
Control
Charge
Pump
Oscillator
Output Voltage
Detection
VOUT
Thermal
Protection
FLG
Delay
GND
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DS9706-02 March 2007
RT9706
Test Circuits
1
2
R
FG
I
Supply
V
VIN
EN
FLG
A
FLG
V
V
VIN
FLG
IN
FLG
C
IN
V
RT9706
S1
IN
C
RT9706
I
IN
LEAK AGE
V
I
OUT
OUT
VOUT
GND
OFF
A
VOUT
GND
A
OFF
EN
ON
R
L
ON
C
R
I
OUT
L
L
3
4
R
FG
V
RDS(ON)
V
I
OUT
V
VIN
FLG
FLG
VOUT
RT9706
VIN
C
IN
RT9706
VOUT
GND
C
V
V
IN
C
IN
IN
V
OUT
OUT
EN
OFF
FLG
EN
R
I
C
ON
L
L
GND
V
CE
OUT
5
R
FG
S2
V
VIN
FLG
FLG
C
IN
RT9706
VOUT
GND
V
IN
V
I
OUT
OUT
OFF
A
EN
ON
R
I
C
S3
L
L
OUT
Note: Above test circuits reflected the graphs shown on “Typical Operating Characteristics ”are as follows :
1
−Turn-On Rising & Falling Time vs. Temperature, Turn-On & Off Response, Flag Response
−Supply Current vs. Input Voltage & Temperature, Switch Off Supply Current vs. Temperature, Turn-Off Leakage Current
vs. Temperature
2
3
4
−On-Resistance vs. Input Voltage & Temperature
−EN Threshold Voltage vs. Input Voltage & Temperature, Flag Delay Time vs. Input Voltage & Temperature, UVLO
Threshold vs. Temperature, UVLO at Rising & Falling
5−Current Limit vs. Input Voltage/Temperature, Short Circuit Current Response, Short Circuit Current vs. Temperature,
Inrush Current Response, Soft-start Response, Ramped Load Response, Current Limit Transient Response, Thermal
Shutdown Response
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RT9706
Absolute Maximum Ratings (Note 1)
z Supply Voltage --------------------------------------------------------------------------------------------------------- 6.5V
z Chip Enable Input Voltage ------------------------------------------------------------------------------------------- −0.3V to 6.5V
z Flag Voltage ------------------------------------------------------------------------------------------------------------ 6.5V
z Power Dissipation, PD @ TA = 25°C
SOT-23-5 ---------------------------------------------------------------------------------------------------------------- 0.4W
z Package Thermal Resistance (Note 4)
SOT-23-5, θJA ---------------------------------------------------------------------------------------------------------- 250°C/W
z Junction Temperature ------------------------------------------------------------------------------------------------- 150°C
z Lead Temperature (Soldering, 10 sec.)--------------------------------------------------------------------------- 260°C
z Storage Temperature Range ---------------------------------------------------------------------------------------- −65°C to 150°C
z ESD Susceptibility (Note 2)
HBM (Human Body Mode) ------------------------------------------------------------------------------------------ 2kV
MM (Machine Mode) -------------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions (Note 3)
z Supply Input Voltage-------------------------------------------------------------------------------------------------- 2V to 5.5V
z Chip Enable Input Voltage ------------------------------------------------------------------------------------------- 0V to 5.5V
z Junction Temperature Range---------------------------------------------------------------------------------------- −40°C to 125°C
z Ambient Temperature Range---------------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VIN = 5V, CIN = COUT = 1μF, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
= 500mA
OUT
Min
--
Typ
100
25
Max Units
Switch On Resistance
R
I
130
45
1
mΩ
DS(ON)
I
I
switch on, V
= Open
= Open
--
SW_ON
OUT
OUT
Supply Current
μA
switch off, V
--
0.1
--
SW_OFF
Logic-Low Voltage
V
IL
V
= 2V to 5.5V, switch off
= 2V to 5.5V, switch on
= 0V to 5.5V
--
0.8
V
IN
EN Threshold
Logic-High Voltage V
V
V
V
2.0
--
--
--
--
V
IH
IN
EN Input Current
I
I
0.01
0.5
μA
μA
μs
A
EN
EN
EN
Output Leakage Current
Output Turn-On Rise Time
Current Limit
= 5V, R
= 0Ω
--
10
--
LEAKAGE
LOAD
T
I
10% to 90% of V
rising
--
400
0.8
ON_RISE
OUT
R
I
=1Ω
LOAD
0.5
1.25
LIM
R
FLG
FLAG Output Resistance
FLAG Off Current
= 1mA
= 5V
--
--
20
400
1
Ω
SINK
I
FLG_OFF
0.01
μA
V
FLG
From fault condition to FLG
assertion
FLAG Delay Time (Note 5)
t
5
12
20
ms
D
Under-voltage Lockout
V
V
IN
Rising
1.3
--
1.7
0.1
--
--
V
V
UVLO
Under-voltage Hysteresis
ΔV
UVLO
To be continued
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RT9706
Parameter
Symbol
Test Conditions
Min
--
Typ
130
20
Max Units
Thermal Shutdown Protection
Thermal Shutdown Hysteresis
--
--
T
°C
°C
SD
--
ΔT
SD
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. Devices are ESD sensitive. Handling precaution recommended.
Note 3. The device is not guaranteed to function outside its operating conditions.
Note 4. θJA is measured in the natural convection at TA = 25°C on a low effective single layer thermal conductivity test board of
JEDEC 51-3 thermal measurement standard.
Note 5. The FLAG delay time is input voltage dependent, see“ Typical Operating Characteristics” graph for further details.
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RT9706
Typical Operating Characteristics
Supply Current vs. Input Voltage
Supply Current vs. Temperature
30
25
20
15
10
5
50
40
30
20
10
0
0
2
2.5
3
3.5
4
4.5
5
5.5
-40
-20
0
20
40
60
80
100 120
(°C)
Temperature
Input Voltage (V)
Switch On Resistance vs. Input Voltage
Switch On Resistance vs. Temperature
0.14
0.12
0.1
160
140
120
100
80
0.08
0.06
0.04
0.02
0
60
40
20
-40
-20
0
20
40
60
80
100 120
2
2.5
3
3.5
4
4.5
5
5.5
Input Voltage (V)
Current Limit vs. Input Voltage
Temperature
(°C)
Current Limit vs. Temperature
2.5
2
1.5
1.25
1
1.5
1
0.75
0.5
0.25
0
0.5
0
-40
-20
0
20
40
60
80
100 120
2
2.5
3
3.5
4
4.5
5
5.5
(°C)
Temperature
Input Voltage (V)
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RT9706
EN Pin Threshold Voltage vs. Input Voltage
EN Pin Threshold Voltage vs. Temperature
2
2
1.6
1.2
0.8
0.4
0
1.6
1.2
0.8
0.4
0
-40
-20
0
20
40
60
80
100 120
2
2.5
3
3.5
4
4.5
5
5.5
(°C)
Temperature
Input Voltage (V)
Flag Delay Time vs. Temperature
FLAG Delay Time vs. Input Voltage
20
16
12
8
25
20
15
10
5
4
0
0
-40
-20
0
20
40
60
80
100 120
2
2.5
3
3.5
4
4.5
5
5.5
Temperature
(°C)
Input Voltage (V)
Turn-Off Leakage Current vs. Temperature
4
Switch Off Supply Current vs. Temperature
0.1
3.5
3
0.06
0.02
-0.02
-0.06
-0.1
2.5
2
1.5
1
0.5
0
-0.5
-40
-20
0
20
40
60
80
100 120
-40
-20
0
20
40
60
80
100 120
(°C)
Temperature
(°C)
Temperature
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RT9706
Turn-Off Falling Time vs. Temperature
Turn-On Rising Time vs. Temperature
600
500
400
300
200
100
0
100
80
60
40
20
0
-40
-20
0
20
40
60
80
100 120
-40
-20
0
20
40
60
80
100 120
Temperature (°C)
Temperature
(°C)
Turn-Off Response
Turn-On Response
CI = 33uF, COUT = 1uF
RL = 30Ω
N
CI = 33uF, COUT = 1uF
RL = 30Ω
N
VEN
(5V/Div)
VEN
(5V/Div)
VOUT
(5V/Div)
VOUT
(5V/Div)
Time (25μs/Div)
Time (100μs/Div)
UVLO at Rising
UVLO at Falling
CI = 33uF, COUT = 1uF
N
CI = 33uF, COUT = 1uF
N
VEN
(1V/Div)
VIN
(1V/Div)
VOUT
(1V/Div)
VOUT
(1V/Div)
Time (1ms/Div)
Time (10ms/Div)
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RT9706
Flag Response with Turn-On Short Current
Flag Response with Over Current
VEN
(5V/Div)
VEN
FLAG
(5V/Div)
(5V/Div)
FLAG
(5V/Div)
VOUT
(5V/Div)
IOUT
IOUT
(500mA/Div)
(500mA/Div)
CI = COUT = 1uF
N
RL = 0Ω
Time (10ms/Div)
Time (2.5ms/Div)
Short Circuit Current Response
Inrush Current Response
COUT = 1000uF
VEN
(5V/Div)
COUT = 220uF
IOUT
(1A/Div)
COUT = 1uF
IOUT
(1A/Div)
CI = COUT = 33uF
N
Time (5ms/Div)
Time (1ms/Div)
Ramped Load Response
Ramped Load Response
VOUT
(1V/Div)
VEN
(5V/Div)
IOUT
(1A/Div)
RL = 1Ω
IOUT
(500mA/Div)
IOUT
RL = Short
(500mA/Div)
RL(H) = 5Ω, RL(L) = 100Ω
Time (50μs/Div)
Time (50ms/Div)
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RT9706
Applications Information
Soft Start for Hot Plug-In Applications
The RT9706 is a single N-Channel MOSFET high-side
power switch with active-low enable input, optimized for
self-powered and bus-powered Universal Serial Bus (USB)
applications. The RT9706 equipped with a charge pump
circuitry to drive the internal NMOS 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.
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 RT9706 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.A100kΩ 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. The FLG response delay time tD
is typically 12ms.
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
RT9706 prevents reverse current flow if VOUT being
externally forced to a higher voltage than VIN when the
output disabled (VEN > 2V).
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.
S
D
S
D
Under-Voltage Lockout
G
G
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.
Normal MOSFET
RT9706
Figure 1
Chip Enable Input
The switch will be disabled when the EN pin is in a logic
high condition. During this condition, the internal circuitry
and MOSFET are turned off, reducing the supply current
to 0.1μA typical. The maximum guaranteed voltage for a
logic low at the EN pin is 0.8V. A minimum guaranteed
voltage of 2V at the EN pin will turn the RT9706 off. Floating
the input may cause unpredictable operation. EN should
not be allowed to go negative with respect to GND.
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 800mA
through the switch of RT9706. 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.
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RT9706
Once this current limit threshold is exceeded the device
enters constant current mode until the thermal shutdown
occurs or the fault is removed.
The maximum power dissipation at TA = 25°C can be
calculated by following formula :
PD(MAX) = (125°C − 25°C) / 250°C/W = 0.4 W for
SOT-23-5 packages
Thermal Shutdown
Thermal shutdown is employed to protect the device from
damage if the die temperature exceeds approximately
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.
The maximum power dissipation depends on operating
ambient temperature for fixed TJ(MAX) and thermal
resistance θJA. For RT9706 packages, the Figure 2 of
derating curves allows the designer to see the effect of
rising ambient temperature on the maximum power
allowed.
0.6
Power Dissipation and Thermal Consideration
Single Layer PCB
The device “S” junction temperature depends on several
factors such as the load, PCB layout, ambient temperature
and package type. The output pin of RT9706 can deliver a
current of up to 500mA, 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
0.5
SOT-23-5
0.4
0.3
0.2
0.1
0
0
25
50
75
100
125
current and the RDS(ON) of switch as below.
Ambient Temperature
(°C)
2
PD = RDS(ON) x (IOUT
)
Figure 2. Derating Curves for RT9706 Package
Although the devices are rated for 500mA 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 :
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.
PD(MAX) = ( TJ(MAX) − TA ) / θJA
PD(MAX) = ( TJ(MAX) − TA ) / θJA
Where TJ(MAX) is the maximum operation junction
temperature, TA is the ambient temperature and the θJA is
the junction to ambient thermal resistance.
For recommended operating conditions specification of
RT9706, where TJ(MAX) is the maximum junction
temperature of the die (125°C) and TA is the maximum
ambient temperature. The junction to ambient thermal
resistance θJA is layout dependent. For SOT-23-5
packages, the thermal resistance θJA is 250°C/W on the
standard JEDEC 51-3 single-layer thermal test board.
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
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.
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RT9706
ABus-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 100mAper port, with a maximum of four
external ports.
Output Filter Capacitor
A low-ESR 150μF aluminum electrolytic or tantalum
between VOUT andGNDis 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.
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.
Fault Flag Filtering (Optional)
The transient inrush current to downstream capacitance
may cause a short-duration error flag, which may cause
erroneous over-current reporting. A simple 1ms RC low-
pass filter (10kΩ and 0.1μF) in the flag line (see Typical
Application Circuit) eliminates short-duration transients.
The faster trip time of the RT9706 power distribution allow
designers to design hubs that can operate through faults.
The RT9706 have low on-resistance and internal fault-
reporting circuitry that help the designer to meet voltage
regulation and fault notification requirements.
Voltage Drop
The USB specification states a minimum port-output
voltage in two locations on the bus, 4.75V out of a Self-
Powered Hub port and 4.4V 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 ).
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.
The following calculation determines VOUT (MIN) for multi-
ple ports (NPORTS) ganged together through one switch (if
using one switch per port, NPORTS is equal to 1) :
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
(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.
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 oneGND)
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RT9706
RSWITCH : Resistance of power switch
(80mΩ typical for RT9706)
z Locate the ceramic bypass capacitors as close as
possible to the VIN pins of the RT9706.
V
V
V
IN
VPCB : PCB voltage drop
BUS
OUT
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.
FLG
If the hub consumes the maximum current (II) of 500mA,
the maximum resistance of the cable is 90mΩ.
GND_BUS
The resistance of the switch is defined as follows :
USB
Controller
EN
GND
RSWITCH = { 4.75V − 4.4V − [ 0.5A x ( 4 x 30mΩ + 2 x
Board Layout
90mΩ) ] − VPCB
}
( 0.1A x NPORTS
)
÷
÷
= (200mV − V
)
( 0.1A x NPORTS )
PCB
ESD
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 RT9706, with its maximum
100mΩ on-resistance over temperature, easily meets this
requirement.
Because USB is a hot insertion and removal system, USB
components (especially the connector pins) are subject
to electrostatic discharge (ESD) and should be qualified
to IEC801.2. The RT9706 is designed to withstand a 8kV
human body mode, as defined in MIL-STD-883C. The
requirements in IEC801.2 are much more stringent and
require additional capacitors for the RT9706 to withstand
the higher ESDenergy.
PCB Layout
In order to meet the voltage drop, droop, and EMI
requirements, careful PCB layout is necessary. The
following guidelines must be considered :
Low-ESR 1μF ceramic bypass capacitors and output
capacitors should be placed as closely as possible to the
VIN and VOUT pins to increase the ESD immunity. The
RT9706 may pass the requirements of IEC 1000-4-2
(EN50082-1) level-4 for 15kVair discharge and 8kV contact
discharge tests when these capacitors are added.
z Keep all VBUS traces as short as possible and use at
least 50-mil, 2 ounce copper for all VBUS traces.
z Avoid vias as much as possible. If vias are necessary,
make them as large as feasible.
z Place a ground plane under all circuitry to lower both
resistance and inductance and improveDC and transient
performance (Use a separate ground and power plans if
possible).
z Place cuts in the ground plane between ports to help
reduce the coupling of transients between ports.
z Locate the output capacitor and ferrite beads as close
to the USB connectors as possible to lower impedance
(mainly inductance) between the port and the capacitor
and improve transient load performance.
z Locate the RT9706 as close as possible to the output
port to limit switching noise.
DS9706-02 March 2007
www.richtek.com
13
RT9706
Outline Dimension
H
D
L
B
C
A
b
A1
e
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min
Max
Min
Max
A
A1
B
0.889
0.000
1.397
0.356
2.591
2.692
0.838
0.080
0.300
1.295
0.152
1.803
0.559
2.997
3.099
1.041
0.254
0.610
0.035
0.000
0.055
0.014
0.102
0.106
0.033
0.003
0.012
0.051
0.006
0.071
0.022
0.118
0.122
0.041
0.010
0.024
b
C
D
e
H
L
SOT-23-5 Surface Mount Package
Richtek Technology Corporation
Headquarter
Richtek Technology Corporation
Taipei Office (Marketing)
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
8F, No. 137, Lane 235, Paochiao Road, Hsintien City
Taipei County, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
Tel: (8862)89191466 Fax: (8862)89191465
Email: marketing@richtek.com
www.richtek.com
14
DS9706-02 March 2007
相关型号：
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