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LM3526-HMWC
Datasheet (NSC)
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Datasheet LM3526-HMWC Datasheet (NSC)

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Page 1
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 applica­tions. The dual port device is ideal for Notebook and desktop PC’s that supply power to more than one port.
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 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 mΩ 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
DS101097-1
DS101097-2
LM3526-H
DS101097-40
DS101097-28
LM3526-L
February 2000
LM3526 Dual Port USB Power Switch and Over-Current Protection
© 2000 National Semiconductor Corporation DS101097 www.national.com
Page 2
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
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Absolute Maximum Ratings (Note 1)
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
= 25˚C)
(Note 2) 700 mW
T
JMAX
(Note 2) 160˚C
Operating Ratings
Supply Voltage Range 2.7V to 5.5V Operating Ambient Range −40˚C to 85˚C Operating Junction Temperature
Range −40˚C to 125˚C Storage Temperature Range −65˚C to +150˚C Lead Temperature
(Soldering, 5 seconds) 260˚C
ESD Rating (Note 3) ESD Rating Output Only
2kV 8kV
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, 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
mΩ
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
VEN=VIN(LM3526-L) VEN= 0V (LM3526-H)
0.01 10 µA
R
FO
FLAG Output Voltage
I
FO
= 10 mA, V
IN
=
5.0V 10 25 ΩI
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 VEN/VEN=0VorVEN/VEN=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
−40˚C ≤ T
J
≤ 85˚C
0.2 1
2
µA
I
DDON
Supply Current Switch-On 115 200 µA
Th
SD
Over-temperature Shutdown Threshold
TJIncreasing, 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), θJA(junction to am-
bient thermal resistance), andT
A
(ambient temperature). The maximumallowablepower dissipation at any temperature is P
DMAX
=
(T
JMAX−TA
)/θJAor the number
given in the Absolute Maximum Ratings, which ever is lower. θ
JA
=
150˚C/W.
Note 3: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ 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
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Page 4
AC 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.
Symbol Parameter Conditions Min Typ Max Units
t
r
OUT Rise Time RL=10Ω 100 µs
t
f
OUT Fall Time RL=10Ω 5µs
t
ON
Turn on Delay, EN to OUT RL=10Ω 150 µs
t
OFF
Turn off Delay, EN to OUT RL=10Ω 5µs
t
OC
Over Current Flag Delay RL=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
DS101097-3
LM3526
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Typical Performance Characteristics V
IN
=
5.0V, I
L
=
500 mA, T
A
=
25˚C unless otherwise specified.
R
ON
vs Temperature
DS101097-4
RONvs Temperature
DS101097-5
Quiescent Current vs Input Voltage
DS101097-6
Quiescent Current vs Temperature
DS101097-7
Current Limit vs Output Voltage
DS101097-8
OC Threshold vs Temperature
DS101097-9
LM3526
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Typical Performance Characteristics V
IN
=
5.0V, I
L
=
500 mA, T
A
=
25˚C unless otherwise
specified. (Continued)
Fault Flag Delay vs Temperature
DS101097-35
Fault Flag Delay vs Temperature
DS101097-36
Under Voltage Lockout (UVLO)
DS101097-34
Under Voltage Lockout Threshold vs Temperature
DS101097-37
Over Current/Current Limit Response
*
DS101097-10
*
Output is shorted to Ground through a 100 mΩ resistor
Short Circuit Response with Thermal Cycling
*
DS101097-11
LM3526
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Page 7
Typical Performance Characteristics V
IN
=
5.0V, I
L
=
500 mA, T
A
=
25˚C unless otherwise
specified. (Continued)
Turn-ON/OFF Response with 47Ω/10µF Load
DS101097-12
Turn-ON/OFF Response with 47Ω/150µF Load
DS101097-13
Thermal Shutdown Response (Port A output shorted
*
)
DS101097-14
*
Port A is shorted to GND through a 100 mΩ resistor
Thermal Shutdown Response (See Notes)
DS101097-29
Enable into a short
DS101097-30
LM3526
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Page 8
Functional Description
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 VINwhen 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 145˚C, the ther­mal shutdown circuitry turns off any switch that is current lim­ited. Non-overloaded switches continue to function normally. If the die temperature rises above 150˚C, both switches are turned off and both fault flag outputs are activated. Hyster­esis ensures that a switch turned off by thermal shutdown will not be turned on again until the die temperature is re­duced to 135˚C. Shorted switches will continue to cycle off and on, due to the rising and falling die temperature, until the short is removed.
UNDERVOLTAGE LOCKOUT
UVLO prevents the MOSFET switch from turning on until in­put voltage exceeds 1.8V (typical).
If input voltage drops below 1.8V (typical), UVLO shuts off the MOSFET switch and signals the fault flag. UVLO func­tions only when device is enabled.
CURRENT LIMIT
FAULT FLAG
The fault flag is an open-drain output capable of sinking 10 mA load current to typically 100 mV above ground.
A parasitic diode exists between the flag pins and V
IN
pin.
Pulling the flag pins to voltages higher than V
IN
will forward bias this diode and will cause an increase in supply current. This diode will also clamp the voltage on the flag pins to a di­ode drop above V
IN
.
The fault flag is active (pulled low) when any of the following conditions are present: under-voltage, current limit, or ther­mal shutdown.
Application Information
FILTERING
The USB specification indicates that “no less than 120 µF tantalum capacitors” must be used on the output of each downstream port. This bulk capacitance provides the short-term transient current needed during a hot plug-in. Current surges caused by the input capacitance of the down stream device could generate undesirable EMI signals. Fer­rite beads in series with all power and ground lines are rec­ommended to eliminate or significantly reduce EMI.
In selecting a ferrite bead, the DC resistance of the wire used must be kept to a minimum to reduce the voltage drop.
A 0.01 µF ceramic capacitor is recommended on each port directly between the V
bus
and ground pins to prevent EMI
damage to other components during the hot-detachment. Adequate capacitance must be connected to the input of the
device to limit the input voltage drop during a hot-plug event to less than 330 mV. For a few tens of µs, the host must sup­ply the in-rush current to the peripheral, charging its bulk ca­pacitance to V
bus
. This current is initially supplied by the in­put capacitor. A 33 µF 16V tantalum capacitor is recommended.
In choosing the capacitors, special attention must be paid to the Effective Series Resistance, ESR, of the capacitors to minimize the IR drop across the capacitor’s ESR.
SOFT START
To eliminate the upstream voltage droop caused by the high in-rush current drawn by the output capacitors, the maximum in-rush current is internally limited to 1.5A.
TRANSIENT OVER-CURRENT DELAY
The LM3526’s 1 ms delay in issuing the fault flag is adequate for most applications. If longer delays are required, an RC fil­ter as shown in
Figure 1
may be used.
DS101097-24
FIGURE 1.
LM3526
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Page 9
Application Information (Continued)
PCB LAYOUT CONSIDERATIONS
In order to meet the USB requirements for voltage drop, droop and EMI, each component used in this circuit must be evaluated for its contribution to the circuit performance. The PCB layout rules and guidelines must be followed.
•
Place the switch as close to the USB connector as pos­sible. Keep all V
bus
traces as short as possible and use at
least 50-mil, 1 ounce copper for all V
bus
traces. Solder
plating the traces will reduce the trace resistance.
•
Avoid vias as much as possible. If vias are used, use mul­tiple vias in parallel and/or make them as large as pos­sible.
•
Place the output capacitor and ferrite beads as close to the USB connector as possible.
•
If ferrite beads are used, use wires with minimum resis­tance and large solder pads to minimize connection re­sistance.
DS101097-23
FIGURE 2. Self-Powered Hub Per-Port Voltage Drop
LM3526
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Typical Applications
DS101097-25
FIGURE 3. Dual-Port USB Self-Powered Hub
DS101097-26
FIGURE 4. Soft-Start Application (Single port shown)
DS101097-27
FIGURE 5. In-rush Current-limit Application
LM3526
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Page 11
Physical Dimensions inches (millimeters) unless otherwise noted
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user.
2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.
National Semiconductor Corporation
Americas Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: support@nsc.com
National Semiconductor Europe
Fax: +49 (0) 180-530 85 86
Email: europe.support@nsc.com Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790
National Semiconductor Asia Pacific Customer Response Group
Tel: 65-2544466 Fax: 65-2504466 Email: ap.support@nsc.com
National Semiconductor Japan Ltd.
Tel: 81-3-5639-7560 Fax: 81-3-5639-7507
www.national.com
See Order Information Table
NS Package Number M08A
LM3526 Dual Port USB Power Switch and Over-Current Protection
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
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