19-2357; Rev 0; 4/02 Current-Limited Switch for Single USB Port Features ♦ 0.5A Guaranteed Output Current ♦ Guaranteed 0.75A Short-Circuit Protection ♦ 10ms Internal Fault-Blanking Timeout ♦ No Fault Signal During Power-Up ♦ Thermal Shutdown Protection ♦ 2.7V to 5.5V Supply Range ♦ 14µA Supply Current ♦ Small 10-Pin µMAX Package Ordering Information PART MAX1931EUB TEMP RANGE PIN-PACKAGE -40°C to +85°C 10µMAX Pin Configuration TOP VIEW IN 1 OUT Applications USB Ports and Hubs 10 OUT 2 MAX1931 9 IN IN 3 8 OUT OUT 4 7 FAULT ON 5 6 GND µMAX Notebook Computers Portable Equipment Docking Stations Typical Operating Circuit Hot Plug-In Power Supplies Battery-Charger Circuits INPUT 2.7V TO 5.5V IN OUT OUTPUT MAX1931 FAULT OFF ON ON GND _______________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX1931 General Description The MAX1931 is a current-limited, 60mΩ 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 (14µA) and shutdown current (1µA) 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 µMAX package. MAX1931 Current-Limited Switch for Single USB Port 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 = +70°C) 10-Pin µMAX (derate 5.6mW/°C above +70°C) ............444mW Operating Temperature Range ............................-40°C to +85°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°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. ELECTRICAL CHARACTERISTICS (VIN = 5V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER Operating Voltage Quiescent Current SYMBOL VIN IQ Off Supply Current Undervoltage Lockout Current Limit RON ILIMIT V ON = GND, IOUT = 0 VIN = 4.4V to 5.5V TA = 0°C to +85°C ON Input Leakage VOL FAULT Output High Leakage Current 0.001 2.0 0.01 Startup Time UNITS 5.5 V 35 µA 1 µA 2.6 V 4 20 60 VIN = 4.4V to 5.5V 110 150 VIN = 3V 640 VIN = 2.7V to 3.6V 2 VIN = 3.7V to 5.5V 2.4 mΩ 72 180 850 1060 mA 500 700 mA 0.8 V V V ON = VIN or GND ±1 µA ISINK = 1mA, VIN = 3V 0.4 V 1 µA 13 ms VIN = V FAULT = 5.5V tFB MAX µA TA = 0°C to +85°C VOUT = 4.5V VIN = 2.7V to 5.5V From overcurrent condition to FAULT assertion 6 10 VIN = 5V, COUT = 150µF, RL = 15Ω, from ON driven low to 50% full VOUT 1 80 200 6 20 Switch Turn-On Time tON ILOAD = 400mA Switch Turn-Off Time tOFF ILOAD = 400mA 2 35 TA = +25°C VIL Thermal Shutdown Threshold Timer running TA = +25°C ON Input Logic Low Voltage Fault-Blanking Timeout Period 14 V ON = VIN VIN = 5.5V, VOUT = GND OUT shorted to GND FAULT Output Logic Low Voltage Timer not running Rising edge, 100mV hysteresis ISC VIH TYP 2.7 Continuous Short-Circuit Current Limit ON Input Logic High Voltage MIN V ON = VIN = VOUT = 5.5V UVLO Off Switch Leakage On-Resistance CONDITIONS 3 165 _______________________________________________________________________________________ ms µs µs °C Current-Limited Switch for Single USB Port MAX1931 ELECTRICAL CHARACTERISTICS (VIN = 5V, TA = -40°C to +85°C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL Operating Voltage VIN Quiescent Current IQ Off Supply Current Undervoltage Lockout UVLO Off Switch Leakage On-Resistance RON Current Limit ILIMIT Continuous Short-Circuit Current Limit ON Input Logic Low Voltage ON Input Logic High Voltage MIN MAX UNITS 5.5 V V ON = GND, IOUT = 0, timer not running 35 µA V ON = VIN = VOUT = 5.5V 2 µA 2.9 V V ON = VIN = 5.5V, VOUT = GND 20 µA VIN = 4.4V to 5.5V 150 VIN = 3V 180 3 Rising edge, 100mV hysteresis VOUT = 4.5V 2.0 600 OUT shorted to GND VIL VIH ON Input Leakage FAULT Output Logic Low Voltage CONDITIONS VOL FAULT Output High Leakage Current VIN = 3V to 5.5V VIN = 3V to 3.6V VIN = 3.7V to 5.5V TYP mΩ 1100 mA 750 mA 0.8 V 2 V 2.4 V ON = VIN or GND ±1 µA ISINK = 1mA, VIN = 3V 0.4 V 1 µA VIN = V FAULT = 5.5V Fault-Blanking Timeout Period tFB From overcurrent condition to FAULT assertion Switch Turn-On Time tON ILOAD = 400mA Switch Turn-Off Time tOFF ILOAD = 400mA 6 1 14 ms 200 µs 20 µs Note 1: Specifications to -40°C are guaranteed by design, not production tested. _______________________________________________________________________________________ 3 Typical Operating Characteristics (VIN = 5V, TA = +25°C, unless otherwise noted.) 10 8 6 4 14 MAX1931 toc03 VON (ON) = VIN (GND) OFF SUPPLY CURRENT (nA) 15 QUIESCENT CURRENT (µA) VIN = 3V 13 12 11 10 1 0.1 10 0.01 1 2 3 4 5 -40 6 -20 V0N (ON) = VIN (GND) 60 80 100 0 20 40 60 TEMPERATURE (°C) NORMALIZED ON-RESISTANCE vs. TEMPERATURE NORMALIZED OUTPUT CURRENT vs. OUTPUT VOLTAGE IOUT = 425mA 1.2 NORMALIZED RON 100 40 1.4 MAX1931 toc04 1000 20 TEMPERATURE (°C) INPUT VOLTAGE (V) OFF SWITCH CURRENT vs. TEMPERATURE 0 10 1 -40 1.0 0.8 0.6 0.4 0.1 -20 0 20 40 60 80 0.8 SHORT-CIRCUIT CURRENT 0.6 0.4 0.2 0 -40 100 -20 0 20 40 60 80 1 2 VIN = 3V 4 TURN-OFF TIME vs. TEMPERATURE 7 MAX1931 toc07 ILOAD = 425mA 140 3 OUTPUT VOLTAGE (V) TURN-ON TIME vs. TEMPERATURE ILOAD = 425mA VIN = 5V 6 120 5 80 tOFF (µs) 100 tON (µs) 0 100 TEMPERATURE (°C) TEMPERATURE (°C) 160 VIN = 5V 4 VIN = 3V 3 60 2 40 1 20 0 0 -40 -20 0 20 40 60 TEMPERATURE (°C) 4 80 100 ILIMIT 1.0 0 -40 80 1.2 0.2 0.01 -20 MAX1931 toc08 0 MAX1931 toc06 9 0 NORMALIZED OUTPUT CURRENT 2 MAX1931 toc05 QUIESCENT CURRENT (µA) VIN = 5V 12 100 MAX1931 toc02 VON (ON) = GND (VIN) IOUT = O 14 16 MAX1931 toc01 16 OFF SUPPLY CURRENT vs. TEMPERATURE QUIESCENT CURRENT vs. TEMPERATURE QUIESCENT CURRENT vs. INPUT VOLTAGE OFF SWITCH CURRENT (nA) MAX1931 Current-Limited Switch for Single USB Port 100 -40 -20 0 20 40 60 80 TEMPERATURE (°C) _______________________________________________________________________________________ 100 5 6 Current-Limited Switch for Single USB Port 8 MAX1931 toc10 MAX1931 toc09 10 CURRENT-LIMIT RESPONSE CURRENT-LIMIT AND FAULT RESPONSE 1 1 2 2 3 3 4 4 6 4 2 IOUT = 850mA VIN = 3V OR 5V -40 -20 2ms/div 10µs/div TEMPERATURE (°C) CH1 = VIN, 200mV/div, AC-COUPLED; CH2 = VOUT, 5V/div; CH3 = VFAULT, 5V/div; CH4 = IOUT, 500mA/div CH1 = VIN, 200mV/div, AC-COUPLED; CH2 = VOUT, 5V/div; CH3 = VFAULT, 5V/div; CH4 = IOUT, 1A/div SWITCH TURN-ON TIME SWITCH TURN-OFF TIME STARTUP TIME (TYPICAL USB APPLICATION) 0 20 40 60 80 100 MAX1931 toc13 1 1 2 2 1 CL = 150µF RL = 15Ω MAX1931 toc14 0 MAX1931 toc12 FAULT-BLANKING TIMEOUT (ms) 12 MAX1931 toc11 FAULT-BLANKING TIMEOUT vs. TEMPERATURE 2 FULL CURRENT LIMIT CHARGES CAPACITOR 3 3 3 4 FOLDBACK CURRENT LIMIT RESISTOR LOAD CURRENT 4 4 20µs/div CH1 = VOUT, 5V/div; CH2 = VON, 5V/div; CH3 = VFAULT, 5V/div; CH4 = IOUT, 200mA/div 1µs/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 _______________________________________________________________________________________ 5 MAX1931 Typical Operating Characteristics (continued) (VIN = 5V, TA = +25°C, unless otherwise noted.) Current-Limited Switch for Single USB Port MAX1931 Pin Description PIN NAME FUNCTION Input. P-channel MOSFET source. Connect all IN pins together and bypass with a 1µF ceramic capacitor to ground. 1, 3, 9 IN 2, 4, 8, 10 OUT Switch Output. P-channel MOSFET drain. Connect all OUT pins together and bypass with a 0.1µF capacitor to ground. 5 ON Active-Low Switch On Input. A logic low turns the switch on. 6 GND 7 FAULT 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 P IN OUT MAX1931 P FAULT 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 The MAX1931 features thermal shutdown. The switch turns off and the FAULT output goes low immediately (no fault blanking) when the junction temperature exceeds +165°C. When the MAX1931 cools 20°C, 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. REPLICA AMPLIFIER ON P ON 10ms TIMER CURRENT-LIMIT AMPLIFIER 1.24V FAULT Indicator HOT GND ON CONTROL CIRCUITRY Figure 1. Functional Diagram The MAX1931 provides a fault output (FAULT). A 100kΩ 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 +165°C. • The device is in current limit and the 10ms faultblanking period is exceeded. 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. 6 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 _______________________________________________________________________________________ Current-Limited Switch for Single USB Port 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 (see Figure 2). Output Capacitor Connect a 0.1µF 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). INPUT 2.7V TO 5.5V IN OUT 1µF 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 (150mΩ 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. Chip Information TRANSISTOR COUNT: 715 OUTPUT MAX1931 0.1µF* MAX1931 100kΩ 1 IN 2 OUT 3 IN 4 OUT 5 ON FAULT OFF ON ON OUT 10 IN 9 OUT 8 FAULT 7 GND 6 GND *USB SPECIFICATIONS REQUIRE A LARGER CAPACITOR Figure 2. Typical Application Circuit Figure 3. IN and OUT Cross Connections for a Single-Layer Board _______________________________________________________________________________________ 7 MAX1931 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. 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 MAX1931 Current-Limited Switch for Single USB Port 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 © 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.