Datasheet LND3526 Datasheet (Linear Dimensions)

LND 3526
DATA SHEET
GENERAL DESCRIPTION
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 140m 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
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
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Absolute Maximum Ratings
ABSOLUTE MAXIMUM RATINGS (note 1)
Parameter Symbol Ratings Units
Input Supply Voltage V Fault Flag Voltage V Fault Flag Current I Output Voltage V Output Current I ENABLE Input Voltage V
Storage Temperature T
Operating Ambient Temperature
FLG
FLG
OUT
OUT
EN
STG
T
IN
A
ELECTRICAL CHARACTERISTICS
TA =25° C, VIN = +5V; unless specified
Parameter Symbol Conditions Min Typ Max Units
LND 3526
+6 V +6 V 50 mA +6 V
Internally limited mA
-0.3 to + 5.5 V
-65 to +150
-40 to +85
°C
°C
I
DDOFF
All Switches OFF OUT= Open (note 3) 0.75 5
Supply Current
I
ENABLE
V Input Threshold (active Low)
V
ENABLE Input Current I
ENABLE Input Capacitance C
Switch resistance R
Output Turn-on Delay T
Output Turn-on Rise Time T
Output Turn-off Delay T
Output Turn-off Fall time T
Output Leakage Current I
Continuous Load Current I Short Circuit Current Limit I
Current Limit Threshold I
Over Temperature Shutdown Threshold
O
Error Flag Output Resistance R
Error Flag Off Current I
Under Voltage Lockout Threshold
UVLO
DDON
ENTL
ENTH
EN
OFF
OL
OUT
SCL
LTH
TTH
FLG
FLG
All switches ON OUT=Open (note 3) 110 160
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=10 each output
RL=10 each output
RL=10 each output
RL=10 each output
F
0V to 5.5V -1
5V 100 140
3.3V 140 180
0.8 1.90 V
2.1 2.4 V
±0.01
1pF
0.5 ms
1ms
120
120
Output disabled, each output 10
Each output 0.5 A ENABLE into Load, VOUT = 4.0V 0.5 0.75 1.25 A Ramped load to enabled output
VOUT<4.0V
TJ(Junction temp) :Increasing :Decreasing
VIN=5V, IL=10mA VIN+3.3V,IL=10mA
V
=5V 0.01 1
FLG
VIN= increasing VIN= decreasing
1.6 2.2 A
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
m
µs
µs
µA
°C
°C
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
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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 140m 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
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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
2.5 3.0
Linear Dimensions, Inc. 445 East Ohio Street, Chicago IL 60611 USA tel 312.321.1810 fax 312.321.1830
3.5
INPUT VOLTAGE (V)
4.5 5.0 5.5
4.0
RESISTANCE (m )
On-Resistance v/s Input Voltage
200
150
100
50
2.5 3.0
3.5
4.0
INPUT VOLTAGE (V)
4.5 5.0 5.5
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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
3.5 4.5
3.0
INPUT VOLTAGE (V)
4.0
5.0 5.5
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 Load Turn-On with 47 Ω/150 µF Load
Active Low Enable In
ut
V
OUT
Turn-Off with 47 Ω/10 µF Load Turn-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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