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PDF LM3543M-H Data sheet ( Hoja de datos )
| Número de pieza | LM3543M-H | |
| Descripción | Triple Port USB Power Distribution Switch and Over-Current Protection | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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March 2001
LM3543
Triple Port USB Power Distribution Switch and
Over-Current Protection
General Description
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.
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.
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,
High-Powered USB Functions, Low-Powered USB Func-
tions, and Bus-Powered USB Hubs can all be powered off a
Root or Self-Powered USB Hub containing the LM3543.
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.
Features
n 90mΩ (typ.) High-Side MOSFET Switch
n 500mA Continuous Current per Port
n 7 ms Fault Flag Delay Filters Hot-Plug Events
n Industry Standard Pin Order
n Short Circuit Protection with Power-Saving Current
Foldback
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
n Ambient Temperature Range: −40˚C to 85˚C
Applications
n USB Root, Self-Powered, and Bus-Powered Hubs
n USB Devices such as Monitors and Printers
n General Purpose High Side Switch Applications
10125832
Functional Diagram
10125833
© 2001 National Semiconductor Corporation DS101258
10125801
www.national.com
1 page  
Typical Performance Characteristics VIN = 5.0, IOUT_X = 500mA, TA = 25˚C unless otherwise
specified.
RON vs Input Voltage
RON vs Junction Temperature
10125805
Quiescent Current, Output(s) Enabled vs
Junction Temperature
10125806
Quiescent Current, Output(s) Disabled vs
Junction Temperature
10125807
Quiescent Current, Output(s) Enabled vs
Input Voltage
10125808
Quiescent Current, Output(s) Disabled vs
Input Voltage
10125809
5
10125810
www.national.com
5 Page 
Typical Applications
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.
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 a 3% supply with 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.
USB Bus-Powered Functions and General In-Rush
Current Limiting 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.
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.
FIGURE 7. Using the LM3543 in USB Bus-Powered Functions
10125831
11 www.national.com
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LM3543M-H.PDF ] | |
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