MAX1922
1A Current-Limited Switch for 2 USB Ports
________________________________________________________________
Maxim Integrated Products
1
OUT
1
2
8
7
OUT
OUTIN
IN
GND
SO
TOP VIEW
3
4
6
5
MAX1922
OC
EN
MAX1922
IN OUTPUTOUT
INPUT
2.7V TO 5.5V
ON
OFF
GND
OC
EN
Typical Operating Circuit
19-2254; Rev 3; 4/09
Pin Configurations
Ordering Information
General Description
The MAX1922 current-limited 70mΩswitch with built-in
fault blanking provides an accurate, preset 1.4A to 2.1A
current limit, making it ideal for dual USB applications.
Its low quiescent supply current (16µA) and standby
current (1µA) conserve battery power in portable appli-
cations. The MAX1922 operates with inputs from 2.7V
to 5.5V, making it ideal for both 3V and 5V systems.
An overcurrent signal (OC) notifies the microprocessor
that the internal current limit has been reached. A 10ms
overcurrent-blanking feature allows momentary faults
(such as those caused when hot-swapping into a
capacitive load) to be ignored, thus preventing false
alarms to the host system. This blanking also prevents
an OC signal from being issued when the device is
powering up.
The MAX1922 has several safety features to ensure that
the USB port is protected. Built-in thermal-overload pro-
tection limits power dissipation and junction tempera-
ture. The device also has accurate internal current-
limiting circuitry to protect the input supply against
overload.
The MAX1922 is offered in a space-saving 8-pin SO
package and a 10-pin TDFN package and operates over
the extended (-40°C to +85°C) temperature range.
Applications
Notebook Computers
USB Ports
USB Hubs
Docking Stations
Features
oAccurate Current Limit (1.4A min, 2.1A max)
o10ms Internal OC Blanking Timeout
oOC Blanking During Power-Up
o125mΩ(max) High-Side MOSFET
oShort-Circuit and Thermal Protection with
Overcurrent Logic Output
oUndervoltage Lockout
o16µA Quiescent Supply Current
o1µA (max) Standby Supply Current
o2.7V to 5.5V Supply Range
oUL Recognized: UL# E211395
PART TEMP RANGE PIN-
PACKAGE
TOP
MARK
MAX1922ESA+ -40°C to +85°C 8 SO —
MAX1922ETB+ -40°C to +85°C 10 TDFN-EP* AQQ
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
*
EP = Exposed paddle.
+
Denotes a lead(Pb)-free/RoHS-compliant package.
Pin Configurations continued at end of data sheet.
MAX1922
1A Current-Limited Switch for 2 USB Ports
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN = 5V, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
IN, EN, OC to GND...................................................-0.3V to +6V
OUT to GND ................................................-0.3V to (VIN + 0.3V)
Maximum Switch Current.........................2.3A (internally limited)
OUT Short-Circuit to GND ..........................................Continuous
Continuous Power Dissipation (TA= +70°C)
8-Pin SO (derate 5.88mW/°C above +70°C)................471mW
10-Pin TDFN (derate 18.5mW/°C above +70°C) .......1481mW
Operating Temperature Range (extended).........-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
OPERATING CONDITION
Input Voltage VIN 2.7 5.5 V
POWER SWITCH
TA = +25°C VIN = 4.4V to 5.5V 70 100
VIN = 4.4V to 5.5V 125
Switch Static Drain-Source On-
State Resistance RDS
(
ON
)
TA = 0°C to +85°C VIN = 3V 72 150
mΩ
Switch Turn-On Time tON ILOAD = 400mA 80 200 µs
Switch Turn-Off Time tOFF ILOAD = 400mA 3 6 20 µs
ENABLE INPUT (EN)
VIN = 2.7V to 3.6V 2.0
EN High-Level Input Voltage VIH VIN = 3.7V to 5.5V 2.4 V
EN Low-Level Input Voltage VIL VIN = 2.7V to 5.5V 0.8 V
EN Input Current VEN = VIN or GND -1 1 µA
Startup Time VIN = 5V, COUT = 150µF from EN driven low
to 50% full VOUT 1ms
CURRENT LIMIT
Overload Output Current ILIMIT Force VOUT to 4.5V 1.4 1.75 2.1 A
Short-Circuit Output Current ISC OUT shorted to GND 1 1.4 A
SUPPLY CURRENT
Supply Current, Low-Level Input VEN = VIN = VOUT = 5.5V 0.002 1 µA
Timer not running 16 25
Supply Current, High-Level
Input IQVEN = 0, IOUT = 0 Timer running 35 µA
TA = +25°C 0.01 2
Supply-Leakage Current VEN = VIN = 5.5V,
VOUT = 0 TA = 0°C to +85°C 15 µA
UNDERVOLTAGE LOCKOUT
Undervoltage Lockout UVLO Rising edge, 100mV hysteresis 2.0 2.4 2.6 V
OVERCURRENT (OC)
OC Threshold 1.1 A
OC Output Low Voltage VOL ISINK = 1mA, VIN = 3V 0.4 V
MAX1922
1A Current-Limited Switch for 2 USB Ports
_______________________________________________________________________________________ 3
Note 1: Specifications to -40°C are guaranteed by design, not production tested.
ELECTRICAL CHARACTERISTICS
(VIN = 5V, TA= -40°C to +85°C, unless otherwise noted.) (Note 1)
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 5V, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
OC Off-State Current VIN = VOC = 5V 1 µA
OC Blanking Timeout Period tBL From overcurrent condition to OC assertion 6 10 13 ms
THERMAL SHUTDOWN
Thermal Shutdown Threshold 165 °C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
OPERATING CONDITION
Input Voltage VIN 3.0 5.5 V
POWER SWITCH
VIN = 4.4V to 5.5V 125
Switch Static Drain-Source
On-State Resistance RDS
(
ON
)
VIN = 3V 150 mΩ
Switch Turn-On Time tON ILOAD = 400mA 200 µs
Switch Turn-Off Time tOFF ILOAD = 400mA 1 20 µs
ENABLE INPUT (EN)
VIN = 3.0V to 3.6V 2.0
EN High-Level Input Voltage VIH VIN = 3.7V to 5.5V 2.4 V
EN Low-Level Input Voltage VIL VIN = 3.0V to 5.5V 0.8 V
EN Input Current VEN = VIN or GND -1 1 µA
CURRENT LIMIT
Overload Output Current ILIMIT Force VOUT to 4.5V 1.2 2.3 A
Short-Circuit Output Current ISC OUT shorted to GND 1.5 A
SUPPLY CURRENT
Supply Current, Low-Level Input VEN = VIN = VOUT = 5.5V 2 µA
Supply Current, High-Level
Input IQVEN = GND, IOUT = 0, timer not running 25 µA
Supply Leakage Current VEN = VIN = 5.5V, VOUT = GND 15 µA
UNDERVOLTAGE LOCKOUT
Undervoltage Lockout UVLO Rising edge, 100mV hysteresis 2.0 2.9 V
OVERCURRENT (OC)
OC Threshold 1.1 A
OC Output Low Voltage VOL ISINK = 1mA, VIN = 3V 0.4 V
OC Off-State Current VIN = VOC = 5V 1 µA
OC Blanking Timeout Period tBL From overcurrent condition to OC assertion 6 14 ms
MAX1922
1A Current-Limited Switch for 2 USB Ports
4 _______________________________________________________________________________________
Typical Operating Characteristics
(Circuit of Figure 2, VIN = 5V, TA = +25°C, unless otherwise noted.)
0
6
4
2
8
10
12
14
16
18
20
0 0.5 2.0 2.51.0 1.5 3.0 3.5 4.0 4.5 5.0 5.5
QUIESCENT CURRENT vs. INPUT VOLTAGE
MAX1922 toc01
INPUT VOLTAGE (V)
QUIESCENT CURRENT (μA)
IOUT = 0
VEN = 0
14.5
14.0
15.5
15.0
16.5
16.0
17.5
17.0
18.0
-40 -15 10 35 60 85
QUIESCENT CURRENT vs. TEMPERATURE
MAX1922 toc02
TEMPERATURE (°C)
QUIESCENT CURRENT (μA)
VIN = 5V
VIN = 3V
IOUT = 0
100
0.01
OFF SUPPLY CURRENT
vs. TEMPERATURE
0.1
1
10
MAX1922 toc03
TEMPERATURE (°C)
OFF SUPPLY CURRENT (nA)
-40 -15 10 35 60 85
EN = IN
OUT = OPEN
0
40
20
80
60
140
120
100
160
-40 -15 10 35 60 85
TURN-ON TIME vs. TEMPERATURE
MAX1922 toc07
TEMPERATURE (°C)
TURN-ON TIME (μs)
IOUT = 850mA
COUT = 0.1μF
VIN = 3V
VIN = 5V
4.0
5.5
6.0
5.0
4.5
7.5
7.0
6.5
8.5
8.0
9.0
-40 10-15 35 60 85
TURN-OFF TIME vs. TEMPERATURE
MAX1922 toc08
TEMPERATURE (°C)
TURN-OFF TIME (μs)
IOUT = 850mA
COUT = 0.1μF
VIN = 3V
VIN = 5V
5
7
6
12
8
9
10
11
14
13
15
-40 -15 10 35 60 85
OC BLANKING TIMEOUT
vs. TEMPERATURE
MAX1922 toc09
TEMPERATURE (°C)
OC BLANKING TIMEOUT (ms)
IOUT = 1.75A
VIN = 3V OR 5V
100
1000
0.01
OFF SWITCH CURRENT
vs. TEMPERATURE
0.1
1
10
MAX1922 toc04
TEMPERATURE (°C)
OFF SWITCH CURRENT (nA)
-40 -15 10 35 60 85
EN = IN
VOUT = 0
-40 -15 35 85
NORMALIZED ON-RESISTANCE
vs. TEMPERATURE
MAX1922 toc05
TEMPERATURE (°C)
NORMALIZED RON
10 60
0.4
0.7
0.6
0.5
0.9
0.8
1.3
1.2
1.1
1.0
1.4
IOUT = 850mA
0
0.4
0.2
0.8
0.6
1.0
1.2
0 0.5 2.0 2.5 3.0 3.51.0 1.5 4.0 4.5 5.0
NORMALIZED OUTPUT CURRENT
vs. OUTPUT VOLTAGE
MAX1922 toc06
OUTPUT VOLTAGE (V)
NORMALIZED OUTPUT CURRENT
SHORT-CIRCUIT CURRENT
ILIMIT(1.75A)
MAX1922
1A Current-Limited Switch for 2 USB Ports
_______________________________________________________________________________________
5
5V
0
0
0
2ms/div
MAX1922 toc10
CURRENT-LIMIT AND OC RESPONSE
VIN AC-COUPLED
100mV/div
VOUT, 5V/div
VOC, 5V/div
IOUT, 1A/div
5V
5V
0
0
4μs/div
MAX1922 toc11
CURRENT-LIMIT RESPONSE
VIN AC-COUPLED
500mV/div
VOUT, 5V/div
IOUT, 2A/div
VOC, 5V/div
5V
0
0
0
20μs/div
MAX1922 toc12
SWITCH TURN-ON TIME
VOUT, 5V/div
IOUT,
500mA/div
VOC, 5V/div
VEN, 5V/div
5V
0
0
0
1μs/div
MAX1922 toc13
SWITCH TURN-OFF TIME
VOUT, 5V/div
IOUT,
500mA/div
VOC, 5V/div
VEN, 5V/div
STARTUP TIME
(TYPICAL USB APPLICATION)
MAX1922 toc14
1ms/div
0
0
5V
0
FULL CURRENT LIMIT CHARGES CAPACITOR
RESISTOR LOAD CURRENT
SHORT-CIRCUIT
CURRENT LIMIT
VOUT 5V/div
VEN 5V/div
IIN 1A/div
VOC 5A/div
Typical Operating Characteristics (continued)
(Circuit of Figure 2, VIN = 5V, TA = +25°C, unless otherwise noted.)
MAX1922
Detailed Description
The MAX1922 p-channel MOSFET power switch limits
output current to 1.4A min and 2.1A max. When the out-
put current increases beyond the current limit (ILIMIT),
the current also increases through the replica switch
(IOUT / 13000). The current-limit error amplifier com-
pares the voltage to the internal 1.24V reference and
regulates the current back to the ILIMIT (Figure 1).
These switches are not bidirectional; therefore, the
input voltage must be higher than the output voltage.
Continuous Short-Circuit Protection
The MAX1922 is a short-circuit-protected switch. In the
event of an output short-circuit condition, the current
through the switch is foldback-current-limited to 1A
continuous.
Thermal Shutdown
The MAX1922 has a thermal shutdown feature. The
switch turns off and the OC output goes low immediate-
ly (no overcurrent blanking) when the junction tempera-
ture exceeds +165°C. When the MAX1922 cools 20°C,
the switch turns back on. If the fault short-circuit condi-
tion is not removed, the switch cycles on and off, result-
ing in a pulsed output.
OC
Indicator
The MAX1922 provides an overcurrent output (OC). A
100kΩpullup resistor from OC to IN provides a logic
control signal. This open-drain output goes low when
any of the following conditions occur:
•The input voltage is below the 2.4V undervoltage
lockout (UVLO) threshold.
•The die temperature exceeds the thermal shutdown
temperature limit of +165°C.
•The device is in current limit for greater than 10ms.
OC
Blanking
The MAX1922 features 10ms overcurrent blanking.
Blanking allows brief current-limit faults, including
momentary short-circuit faults that occur when hot-
swapping a capacitive load, and ensures that no OC is
issued during power-up. When a load transient causes
the device to enter current limit, an internal counter
starts. If the load fault persists beyond the 10ms over-
current blanking timeout, the OC output asserts low.
Ensure that the MAX1922 input is adequately bypassed
to prevent input glitches from triggering spurious OC
Pin Description
MAX1922
P
P
P
OUT
GND
1.24V
N
ON CURRENT-LIMIT
AMPLIFIER
REPLICA
AMPLIFIER
ON
EN
HOT
IN
CONTROL
CIRCUITRY
OC
10ms
TIMER
Figure 1. Functional Diagram
1A Current-Limited Switch for 2 USB Ports
6 _______________________________________________________________________________________
PACKAGE
TDFN SO NAME FUNCTION
61 GND Ground
1, 3, 9 2, 3 IN Inp ut. p - channel M O S FE T sour ce— connect al l IN p i ns tog ether and b yp ass w i th a 1µF cap aci tor g r ound .
54EN Active-Low Switch Enable Input. A logic-low turns on the switch.
75OC Overcurrent-Indicator Output. This open-drain output goes low when the device is in thermal shutdown
or undervoltage lockout, or during a sustained (10ms) current-limit condition.
2, 4,
8, 10
6, 7,
8OUT Switch Output. p-channel MOSFET drain—connect all OUT pins together and bypass with a 0.1µF
capacitor to ground.
——EP
TDFN Only. Exposed paddle. Connect to the GND plane for optimum thermal dissipation. This does not
remove the requirement for a proper ground.
MAX1922
1A Current-Limited Switch for 2 USB Ports
outputs. Input voltage glitches less than 150mV do not
cause a spurious OC output. Load-transient faults less
than 10ms (typ) will not cause an OC output assertion.
Only current-limit faults are blanked. Die overtempera-
ture faults and input voltage droops below the UVLO
threshold will cause an immediate OC output.
Applications Information
Input Capacitor
To limit the input voltage drop during momentary output
short-circuit conditions, connect a capacitor from IN to
GND. A 1µF ceramic capacitor is adequate for most
applications; however, higher capacitor values further
reduce the voltage drop at the input (Figure 2).
Output Capacitor
Connect a 0.1µF capacitor from OUT to GND. This
capacitor helps to prevent inductive parasitics from
pulling OUT negative during turn-off.
Layout and Thermal Dissipation
Important: Optimize the switch response time to output
short-circuit conditions by keeping all traces as short
as possible to reduce the effect of undesirable parasitic
inductance. Place input and output capacitors as close
as possible to the device (no more than 5mm away). All
IN and OUT pins must be connected with short traces
to the power bus. Wide power-bus planes provide
superior heat dissipation through the MAX1922’s IN
and OUT pins. Under normal operating conditions, the
package can dissipate and channel heat away.
Calculate the maximum power dissipation as follows:
P = (ILIMIT)2RON
where ILIMIT is the preset current limit (2.1A max) and
RON is the on-resistance of the switch (125mΩmax).
When the output is short circuited, foldback-current lim-
iting activates and the voltage drop across the switch
equals the input supply voltage. The power dissipated
across the switch increases, as does the die tempera-
ture. If the fault condition is not removed, the thermal-
overload protection circuitry activates (see
Thermal
Shutdown
section). Wide power-bus planes connected
to IN and OUT and a ground plane in contact with the
device help dissipate additional heat.
Driving Inductive Loads
A wide variety of devices (mice, keyboards, cameras,
and printers) can load the USB port. These devices
commonly connect to the port with cables, which can
add an inductive component to the load. This induc-
tance causes the output voltage at the USB port to ring
during a load step. The MAX1922 is capable of driving
inductive loads, but avoid exceeding the device’s
absolute maximum ratings. Usually the load inductance
is relatively small, and the MAX1922 input includes a
substantial bulk capacitance from an upstream regula-
tor as well as local bypass capacitors, limiting over-
shoot. If severe ringing occurs due to large load
inductance, clamp the MAX1922 output below 6V and
above -0.3V.
Figure 2. Typical Application Circuit
MAX1922
IN OUTPUT
OUT
INPUT
1μF0.1μF*
*USB SPECIFICATIONS REQUIRE
A HIGHER VALUE CAPACITOR.
OVERCURRENT
OUTPUT
ON
100kΩ
OFF
GND
OC
EN
_______________________________________________________________________________________ 7
MAX1922
1A Current-Limited Switch for 2 USB Ports
8 _______________________________________________________________________________________
TOP VIEW
1
+
34
10 8 7
MAX1922
2
9
5
6
TDFN
OUT
OUT
OC
IN
IN
OUT
INOUT
GNDEN
Pin Configurations (continued) Chip Information
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns, go
to www.maxim-ic.com/packages.
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
8 SO S8-5 21-0041
10 TDFN-EP T1033-1 21-0137
1A Current-Limited Switch for 2 USB Ports
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________
9
© 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
3 4/09 Fixed typo in UL # 1
MAX1922
