The LND3526, is a dual high side power control
switch, with independent enable and flag
functions optimized for self powered and buspowered 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 140mΩ onresistance 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.
DUAL USB POWER CONTROL SWITCH
FEATURES
• USB specification compliant
• Over-Current Protection
• 2 independent switches
• 140 mΩ maximum on-resistance
• Thermal shutdown
• 5µA 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
The LND3526 is available in active-high and
active-low versions in 8-pin die and SOIC
packages.
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 •
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
www.lineardimensions.com
•
Absolute Maximum Ratings
ABSOLUTE MAXIMUMRATINGS (note 1)
ParameterSymbolRatingsUnits
Input Supply VoltageV
Fault Flag VoltageV
Fault Flag CurrentI
Output VoltageV
Output CurrentI
ENABLE Input VoltageV
Storage TemperatureT
Operating Ambient
Temperature
FLG
FLG
OUT
OUT
EN
STG
T
IN
A
ELECTRICAL CHARACTERISTICS
TA =25° C, VIN = +5V; unless specified
ParameterSymbolConditionsMinTypMaxUnits
LND 3526
+6V
+6V
50mA
+6V
Internally limitedmA
-0.3 to + 5.5V
-65 to +150
-40 to +85
°C
°C
I
DDOFF
All Switches OFF OUT= Open (note 3)0.755
Supply Current
I
ENABLE
V
Input Threshold
(active Low)
V
ENABLE Input CurrentI
ENABLE Input CapacitanceC
Switch resistanceR
Output Turn-on DelayT
Output Turn-on Rise TimeT
Output Turn-off DelayT
Output Turn-off Fall timeT
Output Leakage CurrentI
Continuous Load CurrentI
Short Circuit Current LimitI
Current Limit ThresholdI
Over Temperature Shutdown
Threshold
O
Error Flag Output ResistanceR
Error Flag Off CurrentI
Under Voltage Lockout
Threshold
UVLO
DDON
ENTL
ENTH
EN
OFF
OL
OUT
SCL
LTH
TTH
FLG
FLG
All switches ON OUT=Open (note 3)110160
High to Low Transition
(Turn –on)
Low to High Transition
(Turn-off)
V
EN =
EN
Each switch ON
ON
ON
R
= 500mA
I
OUT
RL=10Ω each output
RL=10Ω each output
RL=10Ω each output
RL=10Ω each output
F
0V to 5.5V-1
5V100140
3.3V140180
0.81.90V
2.12.4V
±0.01
1pF
0.5ms
1ms
120
120
Output disabled, each output10
Each output0.5A
ENABLE into Load, VOUT = 4.0V0.50.751.25A
Ramped load to enabled output
VOUT<4.0V
TJ(Junction temp) :Increasing
:Decreasing
VIN=5V, IL=10mA
VIN+3.3V,IL=10mA
V
=5V0.011
FLG
VIN= increasing
VIN= decreasing
1.62.2A
135
125
10
15
2.5
2.3
1
25
40
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.
µA
µA
µA
mΩ
µs
µs
µA
°C
°C
Ω
Ω
µA
V
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 •
www.lineardimensions.com
•
FUNCTIONAL DESCRIPTION
LND 3526
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
is greater that VIN ,
out
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.
(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.
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:
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 •
Undervoltage Lockout
UVLO (undervoltage lockout) prevents the output
MOSFET from turning on until V
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.
exceeds
IN
www.lineardimensions.com
•
APPLICATIONS INFORMATION
LND 3526
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
ramped down from high impedance to
140mΩ in milliseconds. This R
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.
ON,
ON
that is
Supply Filtering
LDI recommends the use of a 0.1µF
to 1µF 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
LND3526
IN
GND
0.1µF to 1µF
TIMING DIAGRAMS
90%
10%
t
F
t
R
90%
Vout
10%
Output Rise and Fall Times
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 •
www.lineardimensions.com
•
g
LND 3526
V
EN
50%
t
ON
t
OFF
Vout
90%
Active-Low Switch Delay Times
V
EN
50%
t
ON
90%
Vout
Active-Hi
h Switch Delay Times
TYPICAL CHARACTERISTICS
t
(Temp : 25 °C
10%
OFF
10%
Supply On-Current v/s Input Voltage
150
100
µ
CURRENT( A)
50
0
2.53.0
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 •
3.5
INPUT VOLTAGE (V)
4.55.05.5
4.0
Ω
RESISTANCE (m )
On-Resistance v/s Input Voltage
200
150
100
50
2.53.0
3.5
4.0
INPUT VOLTAGE (V)
4.55.05.5
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•
LND 3526
Flag Delay v/s Input Voltage
12
10
8
µ
6
4
DELAY TIME ( s)
2
0
2.5
3.54.5
3.0
INPUT VOLTAGE (V)
4.0
5.05.5
FUNCTIONAL CHARACTERISTICS
Enable Threshold v/s Input Voltage
3.0
2.5
2.5
Turn OFF
3.0
INPUT VOLTAGE (V)
4.0
2.0
1.5
1.0
ENABLE THRESHOLD (V)
0.5
0
Turn ON
4.5
5.55.03.5
Active Low
Enable Input
Error Flag
V
OUT
Thermal Shutdown
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 •
www.lineardimensions.com
•
LND 3526
p
p
p
p
Active Low
Enable In
V
Active Low
Enable In
V
OUT
ut
OUT
ut
Active Low
Enable In
ut
V
OUT
Turn-On with 47 Ω/10 µF LoadTurn-On with 47 Ω/150 µF Load
Active Low
Enable In
ut
V
OUT
Turn-Off with 47 Ω/10 µF LoadTurn-Off with 47 Ω/10 µF Load
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 •
www.lineardimensions.com
•
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