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LM3526 Dual Port USB Power Switch and Over-Current Protection
LM3526
Dual Port USB Power Switch and Over-Current
Protection
General Description
The LM3526 provides Universal Serial Bus standard power
switch and over-current protection for all host port applica-
tions. The dual port device is ideal for Notebook and desktop
PCs that supply power to more than one port.
A 1 ms delay on the fault flag output prevents erroneous
overcurrent reporting caused by in-rush currents during hot-
plug events.
The dual stage thermal protection circuit in the LM3526
provides individual protection to each switch and the entire
device. In a short-circuit/over-current event, the switch dis-
sipating excessive heat is turned off, allowing the second
switch to continue to function uninterrupted.
The LM3526 accepts an input voltage between 2.7V and
5.5V allowing use as a device-based in-rush current limiter
for 3.3V USB peripherals, as well as Root and Self-Powered
Hubs at 5.5V. The Enable inputs accept both 3.3V and 5.0V
logic thresholds.
The small size, low R
ON
, and 1 ms fault flag delay make the
LM3526 a good choice for root hubs as well as per-port
power control in embedded and stand-alone hubs.
Features
n
Compatible with USB1.1 and USB 2.0
n
1 ms fault flag delay filters Hot-Plug events
n
Smooth turn-on eliminates in-rush induced voltage drop
n
UL recognized component: REF# 205202
n
1A nominal short circuit output current protects PC
power supplies
n
Thermal shutdown protects device in direct short
condition
n
500mA minimum continuous load current
n
Small SO-8 package minimizes board space
n
2.7V to 5.5V input voltage range
n
140 m
Max. switch resistance
n
1 µA Max. standby current
n
200 µA Max. operating current
n
Under-voltage lockout (UVLO)
Applications
n
Universal Serial Bus (USB) Root Hubs including
Desktop and Notebook PC
n
USB Monitor Hubs
n
Other Self-Powered USB Hub Devices
n
High Power USB Devices Requiring In-rush Limiting
n
General Purpose High Side Switch Applications
Typical Operating Circuit and Connection Diagram
10109701
10109702
LM3526-H
10109740
10109728
LM3526-L
March 2005
LM3526
Dual
Port
USB
Power
Switch
and
Over-Current
Protection
© 2005 National Semiconductor Corporation
DS101097
www.national.com Ordering Information
Part Number
Enable, Delivery Option
Package Type
LM3526M-H
Active High Enable, 95 units per rail
SO-8,
NS Package Number
M08A
LM3526M-L
Active Low Enable, 95 units per rail
LM3526MX-H
Active High Enable, 2500 units per reel
LM3526MX-L
Active Low Enable, 2500 units per reel
LM3526
www.national.com
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.
Supply Voltage
0.3V to 6V
Output Voltage
0.3V to 6V
Voltage at All Other Pins
0.3V to 5.5V
Power Dissipation (T
A
= 25C)
(Note 2)
700 mW
T
JMAX
(Note 2)
150C
Operating Ratings
Supply Voltage Range
2.7V to 5.5V
Operating Ambient Range
40C to 85C
Operating Junction Temperature
Range
40C to 125C
Storage Temperature Range
65C to +150C
Lead Temperature
(Soldering, 5 seconds)
260C
ESD Rating (Note 3)
ESD Rating Output Only
2kV
8kV
DC Electrical Characteristics
Limits in standard typeface are for T
J
= 25C, and limits in boldface type apply over the full operating temperature range. Un-
less otherwise specified: V
IN
= 5.0V, V
EN
= 0V (LM3526-L) or V
EN
= V
IN
(LM3526-H).
Symbol
Parameter
Conditions
Min
Typ
Max
Units
R
ON
On Resistance
V
IN
= 5V, I
OUT
= 500mA, each switch
100
140
m V
IN
= 2.7V, I
OUT
= 500mA, each switch
110
180
I
OUT
OUT pins continuous
output current
Each Output
0.5
A
I
SC
Short Circuit Output
Current
Each Output (enable into Load) (Note 4)
V
OUT
= 4.0V
V
OUT
= 0.1V
0.5
1.2
1
1.9
1.5
A
OC
THRESH
Over-current Threshold
2.2
3.2
A
I
LEAK
OUT pins Output Leakage
Current
V
EN
= V
IN
(LM3526-L)
V
EN
= 0V (LM3526-H)
0.01
10
µA
R
FO
FLAG Output Voltage
I
FO
= 10 mA, V
IN
= 5.0V
10
25 I
FO
= 10 mA, V
IN
= 3.3V
11
35
I
FO
= 10 mA, V
IN
= 2.7V
12
40
I
EN
EN/EN Leakage Current
V
EN
/V
EN
= 0V or V
EN
/V
EN
= V
IN
0.5
0.5
µA
V
IH
EN/EN Input Logic High
(Note 5)
2.4
1.9
V
V
IL
EN/EN Input Logic Low
(Note 5)
1.7
0.8
V
V
UVLO
Under-Voltage Lockout
Threshold
1.8
V
I
DDOFF
Supply Current
Switch-Off
40C
T
J
85C
0.2
1
2
µA
I
DDON
Supply Current
Switch-On
115
200
µA
Th
SD
Over-temperature
Shutdown Threshold
T
J
Increasing, with no shorted output
T
J
Increasing, with shorted output (s)
T
J
Decreasing (Note 4)
150
145
135
C
I
FH
Error Flag Leakage
Current
V
flag
= 5V
0.01
1
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 power dissipation must be derated at elevated temperatures and is dictated by T
JMAX
(Maximum junction temperature), JA
(junction to
ambient thermal resistance), and T
A
(ambient temperature). The maximum allowable power dissipation at any temperature is P
DMAX
= (T
JMAX
T
A
)/ JA
or the
number given in the Absolute Maximum Ratings, which ever is lower. JA
= 150C/W.
Note 3: The human body model is a 100 pF capacitor discharged through a 1.5 k
resistor into each pin. Enable pin ESD threshold is 1.7kV.
Note 4: Thermal Shutdown will protect the device from permanent damage.
Note 5: For LM3526-L, OFF is EN
2.4V and ON is EN 0.8V. For LM3526-H, OFF is EN 0.8V and ON is EN 2.4V.
LM3526
www.national.com
3 AC Electrical Characteristics
Limits in standard typeface are for T
J
= 25C, and limits in boldface type apply over the full operating temperature range. Un-
less otherwise specified: V
IN
= 5.0V.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
t
r
OUT Rise Time
R
L
= 10 100
µs
t
f
OUT Fall Time
R
L
= 10 5
µs
t
ON
Turn on Delay, EN to OUT
R
L
= 10 150
µs
t
OFF
Turn off Delay, EN to OUT
R
L
= 10 5
µs
t
OC
Over Current Flag Delay
R
L
= 0
1
ms
Pin Description
Pin Number
Pin Name
Pin Function
1, 4
ENA, ENB
(LM3526-L)
ENA, ENB
(LM3526-H)
Enable (Input): Logic-compatible enable inputs.
2, 3
FLAG A
FLAG B
Fault Flag (Output): Active-low, open-drain outputs. Indicates overcurrent, UVLO or thermal
shutdown. *See application section for more information.
6
GND
Ground
7
IN
Supply Input: This pin is the input to the power switch and the supply voltage for the IC.
8, 5
OUT A
OUT B
Switch Output: These pins are the outputs of the high side switch.
Typical Application Circuit
10109703
LM3526
www.national.com
4 Typical Performance Characteristics
V
IN
= 5.0V, I
L
= 500 mA, T
A
= 25C unless otherwise
specified.
R
ON
vs Temperature
R
ON
vs Temperature
10109704
10109705
Quiescent Current vs Input Voltage
Quiescent Current vs Temperature
10109706
10109707
Current Limit vs Output Voltage
OC Threshold vs Temperature
10109708
10109709
LM3526
www.national.com
5 Typical Performance Characteristics
V
IN
= 5.0V, I
L
= 500 mA, T
A
= 25C unless otherwise
specified. (Continued)
Fault Flag Delay vs Temperature
Fault Flag Delay vs Temperature
10109735
10109736
Under Voltage Lockout (UVLO)
Under Voltage Lockout Threshold vs Temperature
10109734
10109737
Over Current/Current Limit Response*
Short Circuit Response with
Thermal Cycling*
10109710
* Output is shorted to Ground through a 100 m
resistor
10109711
LM3526
www.national.com
6 Typical Performance Characteristics
V
IN
= 5.0V, I
L
= 500 mA, T
A
= 25C unless otherwise
specified. (Continued)
Turn-ON/OFF Response with
47
/10µF Load
Turn-ON/OFF Response with
47
/150µF Load
10109712
10109713
Thermal Shutdown Response
(Port A output shorted*)
Thermal Shutdown Response (See Notes)
10109714
* Port A is shorted to GND through a 100 m
resistor
10109729
Enable into a short
10109730
LM3526
www.national.com
7 Functional Description
The LM3526-H and LM3526-L are high side P-Channel
switches with active-high and active-low enable inputs, re-
spectively. Fault conditions turn-off and inhibit turn-on of the
output transistor and activate the open-drain error flag tran-
sistor sinking current to the ground.
INPUT AND OUTPUT
IN (Input) is the power supply connection to the control
circuitry and the source of the output MOSFET.
OUT (Output) is the connection to the drain of the output
MOSFET. In a typical application circuit, current flows
through the switch from IN to OUT towards the load.
If V
OUT
is greater than V
IN
when the switch is enabled,
current will flow from OUT to IN since the MOSFET is
bidirectional.
THERMAL SHUTDOWN
The LM3526 is internally protected against excessive power
dissipation by a two-stage thermal protection circuit. If the
device temperature rises to approximately 145C, the ther-
mal shutdown circuitry turns off any switch that is current
limited. Non-overloaded switches continue to function nor-
mally. If the die temperature rises above 150C, both
switches are turned off and both fault flag