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19-2357; Rev 0; 4/02
Current-Limited Switch for Single USB Port
General Description
The MAX1931 is a current-limited, 60m switch with built-in fault blanking. Its accurate preset current limit of 0.64A to 1.06A makes it ideally suited for USB applications. The device's low quiescent supply current (14A) and shutdown current (1A) conserve battery power in portable applications. The MAX1931 operates with inputs from 2.7V to 5.5V, making it ideal for both 3V and 5V systems. A fault signal notifies the microprocessor that the internal current limit has been reached. A 10ms fault-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 fault blanking also prevents a fault signal from being issued when the device is powering up. In the MAX1931, an output overcurrent condition causes the switch to current limit at 0.64A to 1.06A and FAULT to go low after the 10ms blanking period. When the overcurrent condition is removed, FAULT returns to its high-impedance state. The MAX1931 has several safety features to ensure that the USB port is protected. Built-in thermal overload protection limits power dissipation and junction temperatures. The device has an accurate internal current-limiting circuitry to protect the input supply against overload. The MAX1931 is available in a space-saving 10-pin MAX package. o 0.5A Guaranteed Output Current o Guaranteed 0.75A Short-Circuit Protection o 10ms Internal Fault-Blanking Timeout o No Fault Signal During Power-Up o Thermal Shutdown Protection o 2.7V to 5.5V Supply Range o 14A Supply Current o Small 10-Pin MAX Package
Features
MAX1931
Ordering Information
PART MAX1931EUB TEMP RANGE -40C to +85C PIN-PACKAGE 10MAX
Pin Configuration
TOP VIEW
IN 1 OUT IN OUT ON 2 3 4 5 10 OUT 9 IN OUT FAULT GND
MAX1931
8 7 6
Applications
USB Ports and Hubs Notebook Computers Portable Equipment Docking Stations Hot Plug-In Power Supplies Battery-Charger Circuits
INPUT 2.7V TO 5.5V
MAX
Typical Operating Circuit
IN OUT OUTPUT
MAX1931
FAULT OFF ON ON GND
_______________________________________________________________ Maxim Integrated Products
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Current-Limited Switch for Single USB Port MAX1931
ABSOLUTE MAXIMUM RATINGS
IN, ON (ON), FAULT to GND....................................-0.3V to +6V OUT to GND ................................................-0.3V to (VIN + 0.3V) Maximum Continuous Switch Current .....1.2A (internally limited) OUT Short Circuit to GND ..........................................Continuous Continuous Power Dissipation (TA = +70C) 10-Pin MAX (derate 5.6mW/C above +70C) ............444mW Operating Temperature Range ............................-40C to +85C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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.
ELECTRICAL CHARACTERISTICS
(VIN = 5V, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER Operating Voltage Quiescent Current Off Supply Current Undervoltage Lockout Off Switch Leakage UVLO SYMBOL VIN IQ V ON = GND, IOUT = 0 Timer not running Timer running 2.0 0.01 CONDITIONS MIN 2.7 14 35 0.001 1 2.6 4 A TA = 0C to +85C VIN = 4.4V to 5.5V VIN = 4.4V to 5.5V VIN = 3V 640 72 850 500 60 20 110 150 180 1060 700 0.8 2 2.4 1 0.4 1 6 10 1 80 3 6 165 200 20 13 mA mA V V A V A ms ms s s C m TYP MAX 5.5 35 UNITS V A A V
V ON = VIN = VOUT = 5.5V Rising edge, 100mV hysteresis V ON = VIN VIN = 5.5V, VOUT = GND TA = +25C RON ILIMIT ISC VIL VIH TA = +25C
On-Resistance Current Limit Continuous Short-Circuit Current Limit ON Input Logic Low Voltage ON Input Logic High Voltage ON Input Leakage FAULT Output Logic Low Voltage FAULT Output High Leakage Current Fault-Blanking Timeout Period Startup Time Switch Turn-On Time Switch Turn-Off Time Thermal Shutdown Threshold
TA = 0C to +85C VOUT = 4.5V OUT shorted to GND VIN = 2.7V to 5.5V VIN = 2.7V to 3.6V VIN = 3.7V to 5.5V V ON = VIN or GND
VOL
ISINK = 1mA, VIN = 3V VIN = V FAULT = 5.5V
tFB
From overcurrent condition to FAULT assertion VIN = 5V, COUT = 150F, RL = 15, from ON driven low to 50% full VOUT
tON tOFF
ILOAD = 400mA ILOAD = 400mA
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Current-Limited Switch for Single USB Port
ELECTRICAL CHARACTERISTICS
(VIN = 5V, TA = -40C to +85C, unless otherwise noted.) (Note 1) PARAMETER Operating Voltage Quiescent Current Off Supply Current Undervoltage Lockout Off Switch Leakage On-Resistance Current Limit Continuous Short-Circuit Current Limit ON Input Logic Low Voltage ON Input Logic High Voltage ON Input Leakage FAULT Output Logic Low Voltage FAULT Output High Leakage Current Fault-Blanking Timeout Period Switch Turn-On Time Switch Turn-Off Time tFB tON tOFF VOL VIL VIH RON ILIMIT UVLO SYMBOL VIN IQ V ON = GND, IOUT = 0, timer not running V ON = VIN = VOUT = 5.5V Rising edge, 100mV hysteresis V ON = VIN = 5.5V, VOUT = GND VIN = 4.4V to 5.5V VIN = 3V VOUT = 4.5V OUT shorted to GND VIN = 3V to 5.5V VIN = 3V to 3.6V VIN = 3.7V to 5.5V V ON = VIN or GND ISINK = 1mA, VIN = 3V VIN = V FAULT = 5.5V From overcurrent condition to FAULT assertion ILOAD = 400mA ILOAD = 400mA 1 6 2 2.4 1 0.4 1 14 200 20 600 2.0 CONDITIONS MIN 3 TYP MAX 5.5 35 2 2.9 20 150 180 1100 750 0.8 UNITS V A A V A m mA mA V V A V A ms s s
MAX1931
Note 1: Specifications to -40C are guaranteed by design, not production tested.
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Current-Limited Switch for Single USB Port MAX1931
Typical Operating Characteristics
(VIN = 5V, TA = +25C, unless otherwise noted.)
QUIESCENT CURRENT vs. TEMPERATURE
MAX1931 toc02
QUIESCENT CURRENT vs. INPUT VOLTAGE
MAX1931 toc01
OFF SUPPLY CURRENT vs. TEMPERATURE
VON (ON) = VIN (GND) OFF SUPPLY CURRENT (nA) 10
MAX1931 toc03
16 14 QUIESCENT CURRENT (A) 12 10 8 6 4 2 0 0 1 2 3 4 5 6 INPUT VOLTAGE (V) VON (ON) = GND (VIN) IOUT = O
16 VIN = 5V 15 QUIESCENT CURRENT (A) 14 13 12 11 10 9 -40 -20 0 20 40 60 80 VIN = 3V
100
1
0.1
0.01 100 -40 -20 TEMPERATURE (C) 0 20 40 60 TEMPERATURE (C) 80 100
OFF SWITCH CURRENT vs. TEMPERATURE
MAX1931 toc04
NORMALIZED ON-RESISTANCE vs. TEMPERATURE
IOUT = 425mA 1.2 NORMALIZED RON 1.0 0.8 0.6 0.4
MAX1931 toc05
NORMALIZED OUTPUT CURRENT vs. OUTPUT VOLTAGE
ILIMIT
MAX1931 toc06
1000 V0N (ON) = VIN (GND) OFF SWITCH CURRENT (nA) 100
1.4
1.2 NORMALIZED OUTPUT CURRENT 1.0 0.8 SHORT-CIRCUIT CURRENT 0.6 0.4 0.2 0
10
1
0.1
0.2 0 -40 -20 0 20 40 60 80 100 -40 -20 0 20 40 60 80 100 TEMPERATURE (C) TEMPERATURE (C)
0.01
0
1
2
3
4
5
6
OUTPUT VOLTAGE (V)
TURN-ON TIME vs. TEMPERATURE
MAX1931 toc07
TURN-OFF TIME vs. TEMPERATURE
ILOAD = 425mA VIN = 5V
MAX1931 toc08
160 ILOAD = 425mA 140 120 VIN = 3V
7 6 5 tOFF (s) 4 3 2 1 0
100 tON (s) 80 60 40 20 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (C) VIN = 5V
VIN = 3V
-40
-20
0
20
40
60
80
100
TEMPERATURE (C)
4
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Current-Limited Switch for Single USB Port
Typical Operating Characteristics (continued)
(VIN = 5V, TA = +25C, unless otherwise noted.)
FAULT-BLANKING TIMEOUT vs. TEMPERATURE
MAX1931 toc09
MAX1931
CURRENT-LIMIT AND FAULT RESPONSE
MAX1931 toc10
CURRENT-LIMIT RESPONSE
1
MAX1931 toc11
12 FAULT-BLANKING TIMEOUT (ms) 10 8 6 4 2 0 -40 -20 0 20 40 60 80 IOUT = 850mA VIN = 3V OR 5V
1
2
2
3
3
4 100 2ms/div CH1 = VIN, 200mV/div, AC-COUPLED; CH2 = VOUT, 5V/div; CH3 = VFAULT, 5V/div; CH4 = IOUT, 500mA/div
4 10s/div CH1 = VIN, 200mV/div, AC-COUPLED; CH2 = VOUT, 5V/div; CH3 = VFAULT, 5V/div; CH4 = IOUT, 1A/div
TEMPERATURE (C)
SWITCH TURN-ON TIME
MAX1931 toc12
SWITCH TURN-OFF TIME
MAX1931 toc13
STARTUP TIME (TYPICAL USB APPLICATION)
1
MAX1931 toc14
1 2
1 2 2
CL = 150F RL = 15
FULL CURRENT LIMIT CHARGES CAPACITOR RESISTOR LOAD CURRENT
3
3 3 FOLDBACK CURRENT LIMIT
4 20s/div CH1 = VOUT, 5V/div; CH2 = VON, 5V/div; CH3 = VFAULT, 5V/div; CH4 = IOUT, 200mA/div
4 4 1s/div CH1 = VOUT, 5V/div; CH2 = VON, 5V/div; CH3 = VFAULT, 5V/div; CH4 = IOUT, 200mA/div 1ms/div CH1 = VOUT, 5V/div; CH2 = VON, 5V/div; CH3 = IOUT, 500mA/div; CH4 = VFAULT, 5V/div
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Current-Limited Switch for Single USB Port MAX1931
Pin Description
PIN 1, 3, 9 2, 4, 8, 10 5 6 7 NAME IN OUT ON GND FAULT FUNCTION Input. P-channel MOSFET source. Connect all IN pins together and bypass with a 1F ceramic capacitor to ground. Switch Output. P-channel MOSFET drain. Connect all OUT pins together and bypass with a 0.1F capacitor to ground. Active-Low Switch On Input. A logic low turns the switch on. Ground Fault-Indicator Output. This open-drain output goes low when the device is in thermal shutdown, undervoltage lockout, or on a sustained (>10ms) current-limit condition.
Continuous Short-Circuit Protection
IN P OUT
MAX1931
FAULT P
The MAX1931 is a foldback short-circuit-protected switch. In the event of an output short-circuit or currentoverload condition, the current through the switch is foldback-current-limited to 500mA continuous.
Thermal Shutdown
N REPLICA AMPLIFIER ON P
ON
10ms TIMER HOT ON
CURRENT-LIMIT AMPLIFIER 1.24V
The MAX1931 features thermal shutdown. The switch turns off and the FAULT output goes low immediately (no fault blanking) when the junction temperature exceeds +165C. When the MAX1931 cools 20C, the switch turns back on. If the fault short-circuit condition is not removed, the switch cycles on and off, resulting in a pulsed output.
FAULT Indicator
The MAX1931 provides a fault output (FAULT). A 100k pullup resistor from FAULT 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 undervoltage lockout (UVLO) threshold. * The die temperature exceeds the thermal shutdown temperature limit of +165C. * The device is in current limit and the 10ms faultblanking period is exceeded.
GND
CONTROL CIRCUITRY
Figure 1. Functional Diagram
Fault Blanking
_______________Detailed Description
The MAX1931 P-channel MOSFET power switch limits output current to 0.64A (min) to 1.06A (max). When the output current is increased beyond the current limit (ILIMIT), the current also increases through the replica switch (IOUT / 6500). The current-limit error amplifier compares the voltage to the internal 1.24V reference and regulates the current back to the ILIMIT. This switch is not bidirectional; therefore, the input voltage must be higher than the output voltage.
The MAX1931 features 10ms fault blanking. Fault blanking allows current-limit faults, including momentary short-circuit faults that occur when hot-swapping a capacitive load, and also ensures that no fault 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 fault-blanking timeout, the FAULT output asserts low. Ensure that the MAX1931's input is adequately bypassed to prevent input glitches from triggering spurious FAULT outputs. Input voltage glitches less than 150mV do not cause a
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Current-Limited Switch for Single USB Port
spurious FAULT output. Load-transient faults less than 10ms (typ) do not cause a FAULT output assertion. Only current-limit faults are blanked. Die overtemperature faults and input voltage droops below the UVLO threshold cause an immediate fault output. All IN and all OUT pins must be connected with short traces to the power bus. Wide power bus planes provide superior heat dissipation through the switch IN and OUT pins. Figure 3 shows suggested pin connections for a single-layer board. Under normal operating conditions, the package can dissipate and channel heat away. Calculate the maximum power dissipation as follows: P = (ILIMIT)2 RON where ILIMIT is the preset current limit (1.1A max) and RON is the on-resistance of the switch (150m max). When the output is short-circuited, foldback-current-limiting activates and the voltage drop across the switch equals the input supply. The power dissipated across the switch increases, as does the die temperature. If the fault condition is not removed, the thermal-overload protection circuitry activates (see the 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.
MAX1931
Applications Information
Input Capacitor
To limit the input voltage drop during momentary output short-circuit conditions, connect a capacitor from IN to GND. A 1F ceramic capacitor is adequate for most applications; however, higher capacitor values further reduce the voltage drop at the input (see Figure 2).
Output Capacitor
Connect a 0.1F capacitor from OUT to GND. This capacitor helps prevent inductive parasitics from pulling OUT negative during turn-off.
Layout and Thermal Dissipation
To optimize the switch-response time to output shortcircuit conditions, it is very important to keep all traces as short as possible to reduce the effect of undesirable parasitic inductance. Place input and output capacitors as close to the device as possible (no more than 5mm).
Chip Information
TRANSISTOR COUNT: 715
INPUT 2.7V TO 5.5V 1F 100k
IN
OUT
OUTPUT 0.1F*
MAX1931
1 2 IN OUT IN OUT ON OUT IN OUT FAULT GND 10 9 8 7 6
MAX1931
FAULT OFF ON ON GND 5 3 4
*USB SPECIFICATIONS REQUIRE A LARGER CAPACITOR
Figure 2. Typical Application Circuit
Figure 3. IN and OUT Cross Connections for a Single-Layer Board 7
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Current-Limited Switch for Single USB Port MAX1931
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
10LUMAX.EPS
Note: MAX1931 does not have an exposed pad.
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 _____________________ 8 (c) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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