LND 3526
DUAL USB POWER CONTROL SWITCH
DATA SHEET
GENERAL DESCRIPTION
USB specification compliant
Over-Current
Protection
2 independent switches
140
m
maximum on-resistance
Thermal
shutdown
5A Maximum standby supply current
2.4V typical under-voltage lockout
(UVLO)
3V to 5.5V input
Active-high or active-low ENABLE
versions
Independent open drain fault flag pins
500mA continuous load current per
switch
FEATURES
The LND3526, is a dual high side power control
switch, with independent enable and flag
functions optimized for self powered and bus-
powered universal serial bus (USB) applications.
The LND3526 satisfies the following USB
requirements: Each switch channel supplies up
to 500mA with internal circuitry limiting the fault
current to 750mA. The switch's 140m
on-
resistance meets USB voltage drop
requirements. A flag output is available to
indicate fault conditions to the local USB
controller.
Additional features include: lockout (UVLO) to
ensure that the device remains off until there is a
valid input voltage present, thermal shutdown to
prevent switch failure from high current loads
and 3.3V and 5V logic compatible enable inputs.
The LND3526 is available in active-high and
active-low versions in 8-pin die and SOIC
packages.
APPLICATIONS
USB host and self powered hubs
USB
bus-powered
hubs
USB monitors, printers, cameras and
other USB controlled peripherals
Hot plug-in power supplies
Battery charger circuits
Linear Dimensions, Inc. 445 East Ohio Street, Chicago IL 60611 USA tel 312.321.1810 fax 312.321.1830
www.lineardimensions.com
Absolute Maximum Ratings
Parameter
Symbol
Ratings
Units
Input Supply Voltage
V
IN
+6
V
Fault Flag Voltage
V
FLG
+6
V
Fault Flag Current
I
FLG
50
mA
Output Voltage
V
OUT
+6
V
Output Current
I
OUT
Internally limited
mA
ENABLE Input Voltage
V
EN
-0.3 to + 5.5
V
Storage Temperature
T
STG
-65 to +150
C
Operating Ambient
Temperature
T
A
-40 to +85
C
T
A
=25
C, V
IN
= +5V; unless specified
Parameter
Symbol
Conditions
Min
Typ
Max
Units
I
DDOFF
All Switches OFF OUT= Open (note 3)
0.75
5
A
Supply Current
I
DDON
All switches ON OUT=Open (note 3)
110
160
A
V
ENTL
High to Low Transition
(Turn on)
0.8
1.90
V
ENABLE
Input Threshold
(active Low)
V
ENTH
Low to High Transition
(Turn-off)
2.1
2.4
V
ENABLE Input Current
I
EN
V
EN =
0V to 5.5V
-1
0.01
1
A
ENABLE Input Capacitance
C
EN
1
pF
5V
100
140
Switch resistance
R
ON
Each switch ON
I
OUT
= 500mA
3.3V
140
180
m
Output Turn-on Delay
T
ON
RL=10
each output
0.5
ms
Output Turn-on Rise Time
T
R
RL=10
each output
1
ms
Output Turn-off Delay
T
OFF
RL=10
each output
1
20
s
Output Turn-off Fall time
T
F
RL=10
each output
1
20
s
Output Leakage Current
I
OL
Output disabled, each output
10
A
Continuous Load Current
I
OUT
Each output
0.5
A
Short Circuit Current Limit
I
SCL
ENABLE into Load, VOUT = 4.0V
0.5
0.75
1.25
A
Current Limit Threshold
I
LTH
Ramped load to enabled output
VOUT<4.0V
1.6
2.2
A
Over Temperature Shutdown
Threshold
O
TTH
TJ(Junction temp) :Increasing
:Decreasing
135
125
C
C
Error Flag Output Resistance
R
FLG
VIN=5V, IL=10mA
VIN+3.3V,IL=10mA
10
15
25
40
Error Flag Off Current
I
FLG
V
FLG
=5V
0.01
1
A
Under Voltage Lockout
Threshold
UVLO
VIN= increasing
VIN= decreasing
2.5
2.3
V
Note 1. Exceeding the absolute maximum rating may damage the device
Note 2. The device is not guaranteed to function outside its operating rating
Note 3. Off is
0.8 and on is 2.4V for the LND3526-1. Off is 2.4V and is 0.8V for the LND3526-2. The enable input has
approximately 200mV of hysteresis.
ABSOLUTE MAXIMUM
RATINGS (note 1)
ELECTRICAL CHARACTERISTICS
LND 3526
Linear Dimensions, Inc. 445 East Ohio Street, Chicago IL 60611 USA tel 312.321.1810 fax 312.321.1830
www.lineardimensions.com
LND 3526
FUNCTIONAL DESCRIPTION
Input and Output
IN is power supply connection to the logic
circuitry and the drain of the output MOSFET. In
a typical circuit, current flows from IN to OUT
toward the load. If V
out
is greater that V
IN
,
current will flow form out to in, since the switch is
bi-directional when enabled. The output
MOSFET and driver circuitry are also designed
to allow the MOSFET source to be externally
forced to a higher voltage than the drain (Vout
>Vin) when the switch is disabled. In this
situation, the LND3526 prevents undesirable
current flow from OUT to IN.
Thermal Shutdown
Thermal shutdown is employed to protect the
device from damage should the die temperature
exceed safe margins due mainly to short circuit
faults. Each channel employs its own thermal
sensor. Thermal shutdown shuts off the output
MOSFET and asserts the FLG output if the die
temperature reaches 135
C. The other channel
is not effected.
The LND3526 will automatically reset its output
when the die temperature cools down to 125
C.
The LND3526 output and FLG signal will
continue to cycle on and off until the device is
disabled or the fault is removed.
Depending on PCB layout, package, ambient
temperature etc., it may take several hundred
milliseconds from the incidence of the fault to
the output MOSFET being shut off.
Current-limit response
The current-limit threshold is present internally.
The preset level prevents damage to the output
MOSFET and external load but allows a
minimum current of 0.5A through the output
MOSFET of each channel. The current-limit
circuit senses a portion of the output FET switch
current. The reaction to an overcurrent
condition varies with three scenarios:
(i) Switch Enabled into Short Circuit
If a switch is powered on or enabled into a heavy
load of short circuit, the switch immediately goes
into constant-current mode, reducing the output
voltage. The fault flag goes low until the load is
reduced.
(ii) Short Circuit Applied to Output
When a heavy load is applied, a large transient
current may flow until the current limit circuitry will
respond. Once this occurs, the device limits
current to less than the short-circuit current limit
specification.
(iii) Current-Limit Response
The LND3526 current-limit profile exhibits a small
foldback effect of approximately 500mA. Once
this current-limit threshold is exceeded the device
enters constant-current mode. This constant
current is specified as the short circuit current limit
in the "Electrical Characteristics " table. It is
important to mote that the device will deliver load
current up to the current-limit threshold, which is
typically 1.6A
Fault Flag
FLG is an N-channel, open-drain MOSFET output.
The fault-flag is active (low) for one or more of the
following conditions: undervoltage (while
2V<Vin<2.7), current limit, or thermal shutdown.
Undervoltage Lockout
UVLO (undervoltage lockout) prevents the output
MOSFET from turning on until V
IN
exceeds
approximately 2.5V. In the undervoltage state,
the FLAG will be low. After the switch turns on, if
the voltage drops below approximately 2.3V,
UVLO shuts off the output MOSFET and signals
fault flag. Undervoltage detection functions only
when at least one switch is enabled.
Linear Dimensions, Inc. 445 East Ohio Street, Chicago IL 60611 USA tel 312.321.1810 fax 312.321.1830
www.lineardimensions.com
Enable Input
As with any logic input, the enable pins,
ENA/ENB, must be driven to definitive
logic state at all times. Floating the
input can result in spurious operation.
Do not drive ENA/ENB below GND.
Fault Flag Output
Soft Start
The LND3526 provides a "Soft-Start"
function that ramps up the ON-current to
eliminate any excessive voltage drop
that could occur due to charging a
capacitive load in bus-powered
applications. The "Soft-Start"results
from a switch ON resistance, R
ON,
that is
ramped down from high impedance to
140m
in milliseconds. This R
ON
ramping reduces the inrush current and
related transients occur when charging
capacitive loads; a requirement for
meeting the USB voltage drop
standards for bus-powered applications.
LND 3526
APPLICATIONS INFORMATION
Supply Filtering
LDI recommends the use of a 0.1
F
to 1
F bypass capacitor to control
transients on he power supply pin.
The lack of suitable bypassing can
result in ringing on the IN input when
transients occur. This ringing, due to
supply lead inductance, could
damage LND3526 control circuitry if
the 5.5V maximum input rating is
exceeded.
O 3V to 5.5V
0.1
F to 1F
LND3526
IN
GND
TIMING DIAGRAMS
Output Rise and Fall Times
10%
90%
10%
90%
t
t
R
F
Vout
Linear Dimensions, Inc. 445 East Ohio Street, Chicago IL 60611 USA tel 312.321.1810 fax 312.321.1830
www.lineardimensions.com
TYPICAL CHARACTERISTICS
(Temp : 25
C
t
Vout
ON
t
10%
90%
OFF
50%
VEN
V
90%
OFF
t
Vout
EN
50%
10%
t
ON
Active-Low Switch Delay Times
Active-High Switch Delay Times
LND 3526
Linear Dimensions, Inc. 445 East Ohio Street, Chicago IL 60611 USA tel 312.321.1810 fax 312.321.1830
www.lineardimensions.com
Supply On-Current v/s Input Voltage
CURREN
T( A)
50
100
150
0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
100
150
200
50
RESIST
ANCE (m )
On-Resistance v/s Input Voltage
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