LM3544
Quad Port USB Power Distribution Switch and
Over-Current Protection
General Description
The LM3544 is a quad 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 LM3544 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 LM3544 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 LM3544 switches ensures
the LM3544 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 LM3544.
Added features of the LM3544 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
90m
(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 CB
n
Input Voltage Range: 2.7V to 5.5V
n
5µA 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
10120832
10120833
Functional Diagram
10120801
March 2001
LM3544
Quad
Port
USB
Power
Distribution
Switch
and
Over-Current
Protection
© 2001 National Semiconductor Corporation
DS101208
www.national.com
Connection Diagrams
LM3544-H
16-Pin SOIC
LM3544-L
16-Pin SOIC
10120802
Top View
10120829
Top View
Ordering Information
Part Number
Enable, Delivery Option
Package Type
LM3544M-H
Active High Enable
SO-16
NS Package Number M16A
LM3544M-L
Active Low Enable
LM3544MX-H
Active High Enable, 2500 units per reel
LM3544MX-L
Active Low Enable, 2500 units per reel
Typical Application Circuit
10120804
FIGURE 1. The LM3544 used in a Self-Powered or Root USB Hub
LM3544
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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.
Voltage at IN
X
and OUT
X
pins
-0.3V to 6V
Voltage at EN
X
(EN
X
) and FLAG
X
pins
-0.3V to 5.5V
Power Dissipation
(Note 2)
Internally Limited
Maximum Junction Temperature
150°C
Storage Temperature Range
-65°C to 150°C
Lead Temperature Range
(Soldering, 5 sec.)
260°C
ESD Rating (Note 3)
2 kV
Operating Ratings
Supply Voltage Range
2.7V to 5.5V
Continuous Output Current Range
(Each Output)
0 mA to 500 mA
Junction Temperature Range
-40°C to 125°C
DC Electrical Characteristics
Limits in standard typeface are for T
J
= 25°C, and limits in boldface type apply over the full operating temperature range. Un-
less otherwise specified: V
IN
= 5.0V, EN
X
= V
IN
(LM3544-H) or EN
X
= 0V (LM3544-L).
Symbol
Parameter
Conditions
Min
Typ
Max
Units
R
ON
On Resistance
V
IN
= 5V, I
OUTX
= 0.5A
90
125
m
V
IN
= 3.3V, I
OUTX
= 0.5A
95
130
I
OUT
OUT
X
Continuous Output
Current
3.0V
V
IN
5.5V
0.5
A
I
LEAK-OUT
OUT
X
Leakage Current
EN
X
= 0 (EN
X
= V
IN
);
T
J
= 25°C
0.01
1
µA
EN
X
= 0 (EN
X
= V
IN
);
- 40
T
J
125°C
10
µA
I
SC
OUT
X
Short-Circuit Current
(Note 4)
OUT
X
Connected to GND
0.8
1.25
A
OC
THRESH
Overcurrent Threshold
2.0
3.2
A
V
L_FLAG
FLAG
X
Output-Low Voltage
I(FLAG
X
) = 10 mA
0.1
0.3
V
I
LEAK-FLAG
FLAG
X
Leakage Current
2.7
V
FLAG
5.5V
0.2
1
µA
I
LEAK-EN
EN
x
Input Leakage Current
EN
x
/EN
x
= 0V or
EN
x
/EN
x
= V
IN
-0.5
0.5
µA
V
IH
EN/EN Input Logic High
2.7V
V
IN
5.5V
2.4
V
V
IL
EN/EN Input Logic Low
4.5V
V
IN
5.5V
0.8
V
2.7V
V
IN
4.5V
0.4
V
V
UVLO
Under-Voltage Lockout
Threshold
1.8
V
I
DDON
Operational Supply Current
EN
x
= V
IN
(EN
x
= 0 );
T
J
= 25°C
375
600
µA
EN
x
= V
IN
(EN
x
= 0 );
-40°C
T
J
125°C
800
µA
I
DDOFF
Shutdown Supply Current
EN
x
= 0 (EN
x
= V
IN
);
T
J
= 25°C
1
µA
-40°C
T
J
125°C
5
µA
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
JMAX
), Junction to Ambient Thermal Resistance (
JA
), and
the Ambient Temperature (T
A
). The LM3544 in the 16-pin SOIC package has a T
JMAX
of 150°C and a
JA
of 130°C/W. The maximum allowable power dissipation
at any temperature is P
MAX
= (T
JMAX
- T
A
)/
JA
. Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the part will go into
thermal shutdown.
Note 3: The Human body model is a 100 pF capacitor discharged through a 1.5 k
resistor into each pin.
Note 4: Thermal Shutdown will protect the device from permanent damage.
LM3544
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3
AC Electrical Characteristics
Limits are for T
J
= 25°C and V
IN
= 5.0V.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
t
r
OUT
x
Rise Time (Note 5)
C
L
= 33 µF, I
LOAD
= 500 mA
1.5
ms
t
f
OUT
x
Fall Time (Note 6)
C
L
= 33 µF, I
LOAD
= 500 mA
0.9
ms
t
ON
Turn-on Delay (Note 7)
C
L
= 33 µF, I
LOAD
= 500 mA
2.9
ms
t
OFF
Turn-off Delay (Note 8)
C
L
= 33 µF, I
LOAD
= 500 mA
0.7
ms
t
F
Flag Delay (Note 9)
I
FLAG
= 10 mA
7
ms
Note 5: Time for OUT
x
to rise from 10% to 90% of its enabled steady-state value after EN
x
(EN
x
) is asserted.
Note 6: Time for OUT
x
to fall from 10% to 90% of its enabled steady-state value after EN
x
(EN
x
) is deasserted.
Note 7: Time between EN
x
rising through V
IH
(EN
x
falling through V
IL
) and OUT
x
rising through 90% of its enabled steady-state voltage.
Note 8: Time between EN
x
falling through V
IL
(EN
x
rising through V
IH
) and OUT
x
falling through 10% of its enabled steady-state voltage.
Note 9: Time between EN
x
rising through V
IN
(EN
x
falling through V
IN
) and FLAG
X
falling through 0.3V when OUT
X
is connected to GND.
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.
15, 14, 11, 10
OUT 1, 2, 3, 4
Switch Outputs: These pins are the outputs of the high side switches.
3, 4, 7, 8
LM3544-H: EN 1, 2, 3, 4
(LM3544-L: EN 1, 2, 3, 4)
Enable (Inputs): Active-high (or active-low) logic enable inputs.
16, 13, 12, 9
FLAG 1, 2, 3, 4
Fault Flag (Outputs): Active-low open drain outputs. Indicates over-current,
UVLO or thermal shutdown. See
Application Information
section for more
details.
LM3544
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4
Typical Performance Characteristics
V
IN
= 5.0, I
OUT_X
= 500mA, T
A
= 25°C unless otherwise
specified.
R
ON
vs Input Voltage
R
ON
vs Junction Temperature
10120805
10120806
Quiescent Current, Output(s) Enabled vs
Junction Temperature
Quiescent Current, Output(s) Disabled vs
Junction Temperature
10120807
10120808
Quiescent Current, Output(s) Enabled vs
Input Voltage
Quiescent Current, Output(s) Disabled vs
Input Voltage
10120809
10120810
LM3544
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