LM3543MX-L [NSC]
Triple Port USB Power Distribution Switch and Over-Current Protection; 三重端口USB配电开关和过流保护
| 型号： | LM3543MX-L |
| 厂家： | 
National Semiconductor |
| 描述： | Triple Port USB Power Distribution Switch and Over-Current Protection |
| 文件： | 总12页 (文件大小：318K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
March 2001
LM3543
Triple Port USB Power Distribution Switch and
Over-Current Protection
General Description
Features
n 90mΩ (typ.) High-Side MOSFET Switch
n 500mA Continuous Current per Port
The LM3543 is a triple high-side power switch that is an
excellent choice for use in Root, Self-Powered and
Bus-Powered USB (Universal Serial Bus) Hubs. Indepen-
dent port enables, flag signals to alert USB controllers of
error conditions, controlled start-up in hot-plug events, and
short circuit protection all satisfy USB requirements.
n 7 ms Fault Flag Delay Filters Hot-Plug Events
n Industry Standard Pin Order
n Short Circuit Protection with Power-Saving Current
Foldback
The LM3543 accepts input voltages between 2.7V and 5.5V.
The Enable logic inputs, available in active-high and
active-low versions, can be powered off any voltage in the
2.7V to 5.5V range. The LM3543 limits the continuous
current through a single port to 1.25A (max.) when it is
shorted to ground.
n Thermal Shutdown Protection
n Undervoltage Lockout
n Recognized by UL and Nemko
n Input Voltage Range: 2.7V to 5.5V
n 5 µA Maximum Standby Supply Current
n 16-Pin SOIC Package
The low on-state resistance of the LM3543 switches ensures
the LM3543 will satisfy USB voltage drop requirements,
even when current through a switch reaches 500 mA. Thus,
n Ambient Temperature Range: −40˚C to 85˚C
High-Powered USB Functions, Low-Powered USB Func- Applications
tions, and Bus-Powered USB Hubs can all be powered off a
Root or Self-Powered USB Hub containing the LM3543.
n USB Root, Self-Powered, and Bus-Powered Hubs
n USB Devices such as Monitors and Printers
n General Purpose High Side Switch Applications
Added features of the LM3543 include current foldback to
reduce power consumption in current overload conditions,
thermal shutdown to prevent device failure caused by
high-current overheating, and undervoltage lockout to keep
switches from operating if the input voltage is below
acceptable levels.
10125832
10125833
Functional Diagram
10125801
© 2001 National Semiconductor Corporation
DS101258
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Connection Diagrams
LM3543-H
LM3543-L
16-Pin SOIC
16-Pin SOIC
10125802
10125829
Top View
Top View
Ordering Information
Part Number
Enable, Delivery Option
Package Type
LM3543M-H
LM3543M-L
LM3543MX-H
LM3543MX-L
Active High Enable
Active Low Enable
SO-16
NS Package Number M16A
Active High Enable, 2500 units per reel
Active Low Enable, 2500 units per reel
Typical Application Circuit
10125804
FIGURE 1. The LM3543 used in a Self-Powered or Root USB Hub
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2
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
Lead Temperature Range
(Soldering, 5 sec.)
260˚C
2 kV
ESD Rating (Note 3)
Voltage at INX and OUTX pins
Voltage at ENX(ENX) and FLAGX
pins
−0.3V to 6V
Operating Ratings
Supply Voltage Range
−0.3V to 5.5V
2.7V to 5.5V
Continuous Output Current Range
(Each Output)
Power Dissipation (Note 2)
Internally Limited
0 mA to 500 mA
−40˚C to 125˚C
Junction Temperature Range
Maximum Junction Temperature
Storage Temperature Range
150˚C
−65˚C to 150˚C
DC Electrical Characteristics
Limits in standard typeface are for TJ = 25˚C, and limits in boldface type apply over the full operating temperature range. Un-
less otherwise specified: VIN = 5.0V, ENX = VIN (LM3543-H) or ENX = 0V (LM3543-L).
Symbol
Parameter
Conditions
VIN = 5V, IOUTX = 0.5A
VIN = 3.3V, IOUTX = 0.5A
3.0V ≤ VIN ≤ 5.5V
Min
0.5
Typ
90
Max
125
130
Units
mΩ
A
RON
IOUT
ILEAK-OUT
On Resistance
95
OUTX Continuous Output
Current
OUTX Leakage Current
ENX = 0 (ENX = VIN);
TJ = 25˚C
0.01
1
µA
µA
A
ENX = 0 (ENX = VIN);
− 40 ≤ TJ ≤ 85˚C
10
ISC
OUTX Short-Circuit Current
(Note 4)
OUTX Connected to GND
0.8
1.25
OCTHRESH
VL_FLAG
ILEAK-FLAG
ILEAK-EN
Overcurrent Threshold
FLAGX Output-Low Voltage
FLAGX Leakage Current
ENx Input Leakage Current
2.0
0.1
0.2
3.2
0.3
1
A
V
I(FLAGX) = 10 mA
2.7 ≤ VFLAG ≤ 5.5V
ENx/ENx = 0V or
ENx/ENx = VIN
µA
µA
−0.5
0.5
VIH
VIL
EN/EN Input Logic High
EN/EN Input Logic Low
2.7V ≤ VIN ≤ 5.5V
4.5V ≤ VIN ≤ 5.5V
2.7V ≤ VIN ≤ 4.5V
2.4
V
V
0.8
0.4
Under-Voltage Lockout
Threshold
1.8
V
VUVLO
ENx = VIN (ENx = 0 );
TJ = 25˚C
375
600
800
1
µA
µA
µA
µA
IDDON
Operational Supply Current
Shutdown Supply Current
ENx = VIN (ENx = 0 );
−40˚C ≤ TJ ≤ 125˚C
ENx = 0 (ENx = VIN);
TJ = 25˚C
IDDOFF
−40˚C ≤ TJ ≤ 125˚C
5
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Electrical specifications do not apply when operating the device
beyond its rated operating conditions.
Note 2: The maximum allowable power dissipation is a function of the Maximum Junction Temperature (T
), Junction to Ambient Thermal Resistance (θ ), and
JA
JMAX
the Ambient Temperature (T ). The LM3543 in the 16-pin SOIC package has a T
of 150˚C and a θ of 130˚C/W. The maximum allowable power dissipation
JA
A
JMAX
at any temperature is P
thermal shutdown.
= (T
− T )/θ . Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the part will go into
JMAX A JA
MAX
Note 3: The Human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.
Note 4: Thermal Shutdown will protect the device from permanent damage.
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AC Electrical Characteristics
Limits are for TJ = 25˚C and VIN = 5.0V.
Symbol
Parameter
OUTx Rise Time (Note 5)
OUTx Fall Time (Note 6)
Turn-on Delay (Note 7)
Turn-off Delay (Note 8)
Flag Delay (Note 9)
Conditions
Min
Typ
1.5
0.9
2.9
0.7
7
Max
Units
ms
tr
tf
CL = 33 µF, ILOAD = 500mA
CL = 33 µF, ILOAD = 500mA
CL = 33 µF, ILOAD = 500mA
CL = 33 µF, ILOAD = 500mA
IFLAG = 10 mA
ms
tON
tOFF
tF
ms
ms
ms
Note 5: Time for OUT to rise from 10% to 90% of its enabled steady-state value after EN (EN ) is asserted.
x
x
x
Note 6: Time for OUT to fall from 10% to 90% of its enabled steady-state value after EN (EN ) is deasserted.
x
x
x
Note 7: Time between EN rising through V (EN falling through V ) and OUT rising through 90% of its enabled steady-state voltage.
x
IH
x
IL
x
Note 8: Time between EN falling through V (EN rising through V ) and OUT falling through 10% of its enabled steady-state voltage.
x
IL
x
IH
x
Note 9: Time between EN rising through V (EN falling through V ) and FLAG falling through 0.3V when OUT is connected to GND.
x
IN
x
IN
X
X
Pin Description
Pin Number
Pin Name
Pin Function
2, 6
IN 1, 2
Supply Inputs: These pins are the inputs to the power switches and the supply
input for the IC. In most applications they are connected together externally
and to a single input voltage supply.
1, 5
GND 1, 2
Grounds: Must be connected together and to a common ground.
Switch Outputs: These pins are the outputs of the high side switches.
Enable (Inputs): Active-high (or active-low) logic enable inputs.
15, 14, 11
OUT 1, 2, 3
3, 4, 7
16, 13, 12
8, 9, 10
LM3543-H: EN 1, 2, 3
LM3543-L: EN 1, 2, 3
FLAG 1, 2, 3
Fault Flag (Outputs): Active-low open drain outputs. Indicates over-current,
UVLO or thermal shutdown.
N/C
No Internal Connection.
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4
Typical Performance Characteristics VIN = 5.0, IOUT_X = 500mA, TA = 25˚C unless otherwise
specified.
RON vs Input Voltage
RON vs Junction Temperature
10125805
10125806
Quiescent Current, Output(s) Enabled vs
Junction Temperature
Quiescent Current, Output(s) Disabled vs
Junction Temperature
10125807
10125808
Quiescent Current, Output(s) Enabled vs
Input Voltage
Quiescent Current, Output(s) Disabled vs
Input Voltage
10125810
10125809
5
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Typical Performance Characteristics VIN = 5.0, IOUT_X = 500mA, TA = 25˚C unless otherwise
specified. (Continued)
Short-Circuit Output Current vs
Over-Current Threshold vs
Junction Temperature (Note 10)
Junction Temperature (Note 10)
10125813
10125814
Under-Voltage Lockout (UVLO) Threshold vs
Junction Temperature
Turn-On Delay vs Input Voltage
(CIN = 33 µF, COUT = 33 µF)
10125815
10125811
Turn-Off Delay vs Input Voltage
(CIN = 33 µF, COUT = 33 µF)
Fault Flag Delay Time vs
Junction Temperature
10125812
10125816
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6
Typical Performance Characteristics VIN = 5.0, IOUT_X = 500mA, TA = 25˚C unless otherwise
specified. (Continued)
Turn-On/Turn-Off Response with 47Ω/33µF Load
Turn-On/Turn-Off Response with 10Ω/33µF Load
10125818
10125819
Enable Into a Short (Note 10)
Short Connected to Enabled Device (Note 10)
10125820
10125821
Over-Current Response with Ramped Load
Inrush Current to Downstream Device
on OUT1 and Fixed Load on OUT2 (Note 10)
when LM3543 is Enabled (Note 11)
10125822
10125823
Note 10: Output is shorted to Ground through a 100 mΩ resistor.
Note 11: Load is two capacitors and one resistor in parallel to model an actual USB load condition. The first capacitor has a value of 33 µF to model the LM3543
output capacitor. The second capacitor has a value of 10 µF to model the maximum allowable input capacitance of the downstream device. The resistor is a 47Ω
resistor to model the maximum allowable input resistance of the downstream device.
7
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rapidly discharge through the part, activating current limit
circuitry. The threshold for activating current limiting is 2.0A
(typ.). Protection is achieved by momentarily opening the
MOSFET switch and then gradually turning it on. Turn-on is
halted when the current through the switch reaches the
current-limit level of 1.0A (typ.) The current is held at this
level until either the excessive load/short is removed or the
part overheats and thermal shutdown occurs (see Thermal
Shutdown section, below). The fault flag of a switch is
asserted whenever the switch is current limiting.
Functional Description
Power Switches
The power switches that comprise the three ports of the
LM3543 are N-Channel MOSFETs. They have a typical
on-state drain-to-source resistance of 90 mΩ when the input
voltage is 5 V. When enabled, each switch will supply a 500
mA minimum current to its load. In the unlikely event that a
switch is enabled and the output voltage of that switch is
pulled above the input voltage, the bi-directional nature of
the switch results in current to flow from the output to the
input. When a switch is disabled, current flow through the
switch is prevented in both directions.
If a port on the LM3543 is enabled into a short condition, the
output current of that port will rise to the current-limit level
and hold there.
When a port is in a current-limit condition, the LM3543
senses the output voltage on that port and, if it is less than
1.0V (typ.), will reduce the output current through that port.
This operation is shown in Figure 2, below. The current
reduction, or foldback, reduces power dissipation through
the overloaded MOSFET switch. An additional advantage of
the foldback feature is the reduction of power required from
the source supply when one or more output ports are
shorted.
Charge Pump and Driver
The gate voltages of the high-side NFET power switches are
supplied by an internal charge-pump and driver circuit
combination. The charge pump is
switched-capacitor circuit that efficiently generates voltages
above the LM3543 input supply. The charge pump output is
used to supply a transconductance amplifier driver circuit
that controls the gate voltages of the power switches. Rise
and fall times on the gates are typically kept between 2 ms
and 4 ms to limit large current surges and associated
electromagnetic interference (EMI).
a
low-current
ENABLE (ENx or ENx)
The LM3543 comes in two versions: an active-high enable
version, LM3543-H, and an active-low enable version,
LM3543-L. In the LM3543-H, the ENx pins are active-high
logic inputs that, when asserted, turn on the associated
power supply switch(es). Power supply switches are
controlled by the ENx active-low logic inputs in the
LM3543-L. With all three ports disabled on either version of
the LM3543, less than 5 µA of supply current is consumed.
Both types of enable inputs, active-high and active-low, are
TTL and CMOS logic compatible.
10125817
Input and Output
The power supply to the control circuitry and the drains of the
power-switch MOSFETs are connected to the two input pins,
IN1 and IN2. These two pins are connected externally in
most standard applications. The two ground nodes GND1
and GND2 must be connected externally in all applications.
FIGURE 2. Short-Circuit Output Current (with
Foldback) vs. Output Voltage
Thermal Shutdown
The LM3543 is internally protected against excessive power
dissipation by a two-stage thermal protection circuit. If the
device temperature rises to approximately 145˚C, the
thermal shutdown circuitry turns off any switch that is current
limited. Non-overloaded switches continue to function
normally. If the die temperature rises above 160˚C, all
switches are turned off and all three fault flag outputs are
activated. Hysteresis ensures that a switch turned off by
thermal shutdown will not be turned on again until the die
temperature is reduced to 135˚C. Shorted switches will
continue to cycle off and on, due to the rising and falling die
temperature, until the short is removed.
Pins OUT1, OUT2, and OUT3 are connections to the source
nodes of the power-switch MOSFETs. In a typical application
circuit, current flows through the switches from IN1 and IN2
to OUTx toward the load.
Undervoltage Lockout (UVLO)
Undervoltage Lockout (UVLO) prevents the MOSFET
switches from turning on until the input voltage exceeds a
typical value of 1.8V.
If the input voltage drops below the UVLO threshold, the
MOSFET switches are opened and fault flags are activated.
UVLO flags function only when one or more of the ports is
enabled. Due to the paired nature of the design, both FLAG1
and FLAG2 will assert if either port1 or port2 is enabled in a
UVLO condition.
The thermal shutdown function is shown graphically in
Figure 3 and Figure 4.
Current Limit and Foldback
The current limit circuit is designed to protect the system
supply, the LM3543 switches, and the load from potential
damage resulting from excessive currents. If a direct short
occurs on an output of the LM3543, the input capacitor(s)
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8
Soft Start
Functional Description (Continued)
When a power switch is enabled, high levels of current will
flow instantaneously through the LM3543 to charge the large
capacitance at the output of the port. This is likely to exceed
the over-current threshold of the device, at which point the
LM3543 will enter its current-limit mode. The amount of
current used to charge the output capacitor is then set by the
current-limit circuitry. The device will exit the current-limit
mode when the current needed to continue to charge the
output capacitor is less than the LM3543 current-limit level.
Fault Flag
The fault flags are open-drain outputs, each capable of
sinking up to a 10 mA load current to typically 100 mV above
ground.
A parasitic diode exists between the flag pins and VIN pins.
Pulling the flag pins to voltages higher than VIN will forward
bias this diode and will cause an increase in supply current.
This diode will also clamp the voltage on the flag pins to a
10125825
FIGURE 3. Thermal Shutdown Characteristics when
only the First-Stage Thermal-Shutdown Mode is
Needed
diode drop above VIN
.
The fault flag is active (pulled low) when any of the following
conditions are present: under-voltage, current-limit, or
thermal-shutdown.
The LM3543 has an internal delay in reporting fault
conditions that is typically 7 ms in length. In start-up, the
delay gives the device time to charge the output capacitor(s)
and exit the current-limit mode before a flag signal is set.
This delay also prevents flag signal glitches from occurring
when brief changes in operating conditions momentarily
place the LM3543 into one of its three error conditions. If an
error condition still exists after the delay interval has
elapsed, the appropriate fault flag(s) will be asserted (pulled
low) until the error condition is removed. In most
applications, the 7 ms internal flag delay eliminates the need
to extend the delay with an external RC delay network.
Application Information
10125826
Output Filtering
The schematic in Figure 1 showed a typical application
circuit for the LM3543. The USB specification requires 120
µF at the output of each hub. A three-port hub with 33 µF
tantalum capacitors at each port output meets the
specification. These capacitors provide short-term transient
current to drive downstream devices when hot-plug events
occur. Capacitors with low equivalent-series-resistance
should be used to lower the inrush current flow through the
LM3543 during a hot-plug event.
FIGURE 4. Thermal Shutdown Characteristics when
Both First-Stage and Second-Stage Thermal-Shutdown
Modes are Needed
In Figure 3, port 1 is enabled into a short. When this occurs,
the MOSFET switch of port 1 repeatedly opens and closes
as the device temperature rises and falls between 145˚C and
135˚C. In this example, the device temperature never rises
above 160˚C. The second stage thermal shutdown is not
used and port 2 remains operational.
The rapid change in currents seen during a hot plug event
can generate electromagnetic interference (EMI). To reduce
this effect, ferrite beads in series between the outputs of the
LM3543 and the downstream USB port are recommended.
Beads should also be placed between the ground node of
the LM3543 and the ground nodes of connected
downstream ports. In order to keep voltage drop across the
beads to a minimum, wire with small DC resistance should
be used through the ferrite beads. A 0.01 µF - 0.1 µF ceramic
capacitor is recommended on each downstream port directly
between the Vbus and ground pins to further reduce EMI
effects.
When port 1 is enabled into a short in the example illustrated
in Figure 4, the device temperature immediately rises above
160˚C. A higher ambient temperature or a larger number of
shorted outputs can cause the junction temperature to
increase, resulting in the difference in behavior between the
current example and the previous one. When the junction
temperature reaches 160˚C, all three ports are disabled (port
3 is not shown in the figure) and all three fault-flag signals
are asserted. Just prior to time index 2.5 ms, the device
temperature falls below 135˚C, all three ports activate, and
all three fault flags are removed. The short condition remains
on port 1, however. For the remainder of the example, the
device temperature cycles between 135˚C and 145˚C,
causing port 1 to repeatedly turn on and off but allowing the
un-shorted ports to function normally.
Power Supply Filtering
A sizable capacitor should be connected to the input of the
LM3543 to ensure the voltage drop on this node is less than
330 mV during a heavy-load hot-plug event. A 33 µF, 16V
9
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Performance Characteristics section of this datasheet. Next,
calculate the power dissipation through the switch with
Application Information (Continued)
tantalum capacitor is recommended. The input supply
should be further bypassed with a 0.01 µF - 0.1 µF ceramic
capacitor, placed close to the device. The ceramic capacitor
reduces ringing on the supply that can occur when a short is
present at the output of a port.
Equation (1).
2
*
PD = RON IDS
(1)
Note: Equation for power dissipation neglects portion that
comes from LM3543 quiescent current because this value
will almost always be insignificant.
Using this figure, determine the junction temperature with
Equation (2).
Extending the Fault Flag Delay
While the 7 ms (typical) internal delay in reporting flag
conditions is adequate for most applications, the delay can
be extended by connecting external RC filters to the FLAG
pins, as shown in Figure 5.
*
TJ = PD θJA + TA.
(2)
Where:
θJA = SOIC Thermal Resistance: 130˚C/W and TA = Ambient
Temperature (˚C).
Compare the calculated temperature with the expected
temperature used to estimate RON. If they do not reasonably
match, re-estimate RON using a more appropriate operating
temperature and repeat the calculations. Reiterate as
necessary.
PCB Layout Considerations
In order to meet the USB requirements for voltage drop,
droop and EMI, each component used in this circuit must be
evaluated for its contribution to the circuit performance.
These principles are illustrated in Figure 6. The following
PCB layout rules and guidelines are recommended
10125828
FIGURE 5. Typical Circuit for Lengthening the Internal
Flag Delay
1. Place the switch as close to the USB connector as
possible. Keep all Vbus traces as short as possible and
use at least 50-mil, 1 ounce copper for all Vbus traces.
Solder plating the traces will reduce the trace resistance.
Power Dissipation and Junction Temperature
A few simple calculations will allow a designer to calculate
the approximate operating temperature of the LM3543 for a
given application. The large currents possible through the
low resistance power MOSFET combined with the high
thermal resistance of the SOIC package, in relation to power
packages, make this estimate an important design step.
2. Avoid vias as much as possible. If vias are used, use
multiple vias in parallel and/or make them as large as
possible.
3. Place the output capacitor and ferrite beads as close to
the USB connector as possible.
Begin the estimate by determining RON at the expected
operating temperature using the graphs in the Typical
4. If ferrite beads are used, use wires with minimum
resistance and large solder pads to minimize connection
resistance.
10125827
FIGURE 6. Self-Powered Hub Connections and Per-Port Voltage Drop
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10
USB Bus-Powered Functions and General In-Rush
Current Limiting Applications
Typical Applications
The LM3543 can be placed at the power-supply input of USB
bus-powered functions, or other similar devices, to protect
them from high in-rush currents. If the current being
delivered to the device were to exceed the 2.0A over-current
threshold (typ.) of the LM3543, switches in violation would
open to protect the device from damage.
Root and Self-Powered USB Hubs
The LM3543 has been designed primarily for use in root and
self-powered USB hubs. In this application, the switches of
the LM3543 are used to connect the power source of the hub
to the power bus used by downstream devices and to protect
the hub from dangerously excessive loads and shorts to
ground. A high-power bus-powered function, low-power
bus-powered function, or a bus-powered hub can be driven
through a single port of the LM3543. A schematic of a circuit
that uses the LM3543 for power-supply switching in a typical
root or self-powered hub was shown earlier in this datasheet
in Figure 1.
In addition to in-rush current limiting, the LM3543 can be
used in high-power bus-powered functions to keep current
levels of the function in compliance during power-up. The
USB specification requires the staged switching of power
when connecting high-power functions to the bus. When a
high-power function is initially connected to the bus, it must
not draw more than one unit supply (100mA). After a
connection is detected and enumerated, and if the upstream
device is capable of supplying the required power, the
high-power function may draw up to five unit loads (500mA).
With the proper control signals, the LM3543 can be used to
achieve this staged power connection. When the function is
connected to the bus, one or more of the LM3543 switches
can be closed to connect bus power only to circuitry needed
during the connection and enumeration process. If the
function is to be powered fully, remaining switches on the
LM3543 can be closed to connect all blocks of the function to
the power bus. Figure 7 illustrates how the LM3543 can be
connected for use in bus powered functions.
Voltage drop requirements of USB power supplies require
the power outputs of the root and self-powered hubs to be no
less than 4.75V. For this reason, it is recommended that a 5V
±
power supply with a 3% output voltage tolerance is used in
this application. Combining 3% supply with
a
a
low-resistance PCB design and the low on-resistance of the
LM3543 power switches will ensure that the hub power
outputs meet the USB voltage drop specification even with a
500mA load, the maximum allowed in the USB standard.
Bus-Powered USB Hubs
The LM3543 is capable of performing the power supply
switching functions required in Bus-Powered hubs. Use here
is very similar to the configuration used in root and
self-powered hubs. With bus-powered hubs, however, there
is no internal power supply to drive the input pins of the
LM3543. Instead, the input pins should be connected to the
power bus supplied by the upstream hub.
10125831
FIGURE 7. Using the LM3543 in USB Bus-Powered Functions
11
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Physical Dimensions inches (millimeters)
unless otherwise noted
Order Number LM3543M-H, LM3543M-L, LM3543MX-H or LM3543MX-L
NS Package Number M16A
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National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
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