19-2254; Rev 3; 4/09 1A Current-Limited Switch for 2 USB Ports The MAX1922 current-limited 70mΩ switch 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 applications. 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. Features o Accurate Current Limit (1.4A min, 2.1A max) o 10ms Internal OC Blanking Timeout o OC Blanking During Power-Up o 125mΩ (max) High-Side MOSFET o Short-Circuit and Thermal Protection with Overcurrent Logic Output o Undervoltage Lockout o 16µA Quiescent Supply Current o 1µA (max) Standby Supply Current o 2.7V to 5.5V Supply Range o UL Recognized: UL# E211395 The MAX1922 has several safety features to ensure that the USB port is protected. Built-in thermal-overload protection limits power dissipation and junction temperature. The device also has accurate internal currentlimiting 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 Ordering Information PINPACKAGE PART TEMP RANGE MAX1922ESA+ -40°C to +85°C 8 SO MAX1922ETB+ -40°C to +85°C 10 TDFN-EP* TOP MARK — AQQ *EP = Exposed paddle. +Denotes a lead(Pb)-free/RoHS-compliant package. USB Ports USB Hubs Docking Stations Pin Configurations TOP VIEW Typical Operating Circuit INPUT 2.7V TO 5.5V IN GND 1 8 OUT IN 2 7 OUT IN 3 6 OUT EN 4 5 OC OUT OUTPUT MAX1922 MAX1922 OC OFF ON SO EN GND Pin Configurations continued at end of data sheet. ________________________________________________________________ Maxim Integrated Products 1 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. MAX1922 General Description MAX1922 1A Current-Limited Switch for 2 USB Ports ABSOLUTE MAXIMUM RATINGS 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 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 SYMBOL CONDITIONS MIN TYP MAX UNITS 5.5 V OPERATING CONDITION Input Voltage VIN 2.7 POWER SWITCH Switch Static Drain-Source OnState Resistance TA = +25°C RDS(ON) TA = 0°C to +85°C Switch Turn-On Time tON ILOAD = 400mA Switch Turn-Off Time tOFF ILOAD = 400mA VIN = 4.4V to 5.5V 70 VIN = 4.4V to 5.5V 100 125 VIN = 3V 3 mΩ 72 150 80 200 µs 6 20 µs ENABLE INPUT (EN) EN High-Level Input Voltage VIH EN Low-Level Input Voltage VIL VIN = 2.7V to 3.6V 2.0 VIN = 3.7V to 5.5V 2.4 V VIN = 2.7V to 5.5V EN Input Current VEN = VIN or GND Startup Time VIN = 5V, COUT = 150µF from EN driven low to 50% full VOUT -1 0.8 V 1 µA 1 ms CURRENT LIMIT Overload Output Current Short-Circuit Output Current ILIMIT ISC Force VOUT to 4.5V 1.4 OUT shorted to GND 1.75 2.1 A 1 1.4 A µA SUPPLY CURRENT Supply Current, Low-Level Input Supply Current, High-Level Input VEN = VIN = VOUT = 5.5V IQ VEN = 0, IOUT = 0 VEN = VIN = 5.5V, VOUT = 0 Supply-Leakage Current 0.002 1 Timer not running 16 25 Timer running 35 TA = +25°C 0.01 TA = 0°C to +85°C 2 15 µA µA UNDERVOLTAGE LOCKOUT Undervoltage Lockout UVLO Rising edge, 100mV hysteresis 2.0 2.4 2.6 V 0.4 V OVERCURRENT (OC) OC Threshold OC Output Low Voltage 2 1.1 VOL ISINK = 1mA, VIN = 3V _______________________________________________________________________________________ A 1A Current-Limited Switch for 2 USB Ports (VIN = 5V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL OC Off-State Current OC Blanking Timeout Period CONDITIONS MIN TYP MAX 1 µA 6 10 13 ms VIN = VOC = 5V tBL From overcurrent condition to OC assertion UNITS THERMAL SHUTDOWN Thermal Shutdown Threshold 165 °C ELECTRICAL CHARACTERISTICS (VIN = 5V, TA = -40°C to +85°C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 5.5 V OPERATING CONDITION Input Voltage VIN 3.0 POWER SWITCH Switch Static Drain-Source On-State Resistance RDS(ON) VIN = 4.4V to 5.5V 125 VIN = 3V 150 Switch Turn-On Time tON ILOAD = 400mA Switch Turn-Off Time tOFF ILOAD = 400mA 1 mΩ 200 µs 20 µs ENABLE INPUT (EN) EN High-Level Input Voltage VIH EN Low-Level Input Voltage VIL EN Input Current VIN = 3.0V to 3.6V 2.0 VIN = 3.7V to 5.5V 2.4 VIN = 3.0V to 5.5V V 0.8 V VEN = VIN or GND -1 1 µA Force VOUT to 4.5V 1.2 2.3 A 1.5 A VEN = VIN = VOUT = 5.5V 2 µA VEN = GND, IOUT = 0, timer not running 25 µA VEN = VIN = 5.5V, VOUT = GND 15 µA 2.9 V 0.4 V CURRENT LIMIT Overload Output Current Short-Circuit Output Current ILIMIT ISC OUT shorted to GND SUPPLY CURRENT Supply Current, Low-Level Input Supply Current, High-Level Input IQ Supply Leakage Current UNDERVOLTAGE LOCKOUT Undervoltage Lockout UVLO Rising edge, 100mV hysteresis 2.0 OVERCURRENT (OC) OC Threshold 1.1 OC Output Low Voltage VOL ISINK = 1mA, VIN = 3V tBL From overcurrent condition to OC assertion OC Off-State Current OC Blanking Timeout Period VIN = VOC = 5V 6 A 1 µA 14 ms Note 1: Specifications to -40°C are guaranteed by design, not production tested. _______________________________________________________________________________________ 3 MAX1922 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (Circuit of Figure 2, VIN = 5V, TA = +25°C, unless otherwise noted.) 17.5 14 12 10 8 6 4 17.0 16.5 15.5 VIN = 3V 15.0 EN = IN OUT = OPEN 10 1 0.1 14.5 2 0.01 14.0 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 -40 -15 10 35 60 85 TEMPERATURE (°C) 10 35 TEMPERATURE (°C) OFF SWITCH CURRENT vs. TEMPERATURE NORMALIZED ON-RESISTANCE vs. TEMPERATURE NORMALIZED OUTPUT CURRENT vs. OUTPUT VOLTAGE 1.2 1 1.1 1.0 0.9 0.8 0.7 0.6 0.1 1.2 NORMALIZED OUTPUT CURRENT 10 IOUT = 850mA 1.3 NORMALIZED RON 100 MAX1922 toc05 1.4 MAX1922 toc04 EN = IN VOUT = 0 -40 -15 60 85 MAX1922 toc06 INPUT VOLTAGE (V) 1000 OFF SWITCH CURRENT (nA) VIN = 5V 16.0 100 MAX1922 toc03 16 IOUT = 0 OFF SUPPLY CURRENT (nA) 18.0 MAX1922 toc02 VEN = 0 IOUT = 0 QUIESCENT CURRENT (μA) QUIESCENT CURRENT (μA) 18 MAX1922 toc01 20 OFF SUPPLY CURRENT vs. TEMPERATURE QUIESCENT CURRENT vs. TEMPERATURE QUIESCENT CURRENT vs. INPUT VOLTAGE ILIMIT(1.75A) 1.0 0.8 0.6 SHORT-CIRCUIT CURRENT 0.4 0.2 0.5 0.4 10 35 TEMPERATURE (°C) 60 0 -40 85 TURN-ON TIME vs. TEMPERATURE 140 IOUT = 850mA COUT = 0.1μF VIN = 3V 100 80 60 VIN = 5V 40 35 60 85 0 OUTPUT VOLTAGE (V) TURN-OFF TIME vs. TEMPERATURE OC BLANKING TIMEOUT vs. TEMPERATURE IOUT = 850mA COUT = 0.1μF 8.0 7.5 7.0 VIN = 5V 6.5 6.0 VIN = 3V 5.5 15 13 12 11 10 9 8 7 4.5 6 0 4.0 10 35 TEMPERATURE (°C) 60 85 VIN = 3V OR 5V IOUT = 1.75A 14 20 -15 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 TEMPERATURE (°C) 5.0 -40 4 8.5 TURN-OFF TIME (μs) 120 10 9.0 MAX1922 toc07 160 -15 OC BLANKING TIMEOUT (ms) -15 MAX1922 toc08 -40 MAX1922 toc09 0.01 TURN-ON TIME (μs) MAX1922 1A Current-Limited Switch for 2 USB Ports 5 -40 -15 10 35 TEMPERATURE (°C) 60 85 -40 -15 10 35 TEMPERATURE (°C) _______________________________________________________________________________________ 60 85 1A Current-Limited Switch for 2 USB Ports CURRENT-LIMIT RESPONSE CURRENT-LIMIT AND OC RESPONSE MAX1922 toc11 MAX1922 toc10 5V VIN AC-COUPLED 500mV/div VIN AC-COUPLED 100mV/div 5V VOUT, 5V/div 0 VOUT, 5V/div 5V VOC, 5V/div 0 VOC, 5V/div 0 IOUT, 2A/div IOUT, 1A/div 0 0 4μs/div 2ms/div SWITCH TURN-ON TIME SWITCH TURN-OFF TIME MAX1922 toc12 MAX1922 toc13 VOUT, 5V/div VOUT, 5V/div 0 0 VEN, 5V/div VEN, 5V/div 0 0 VOC, 5V/div 5V 5V VOC, 5V/div IOUT, 500mA/div IOUT, 500mA/div 0 0 20μs/div 1μs/div STARTUP TIME (TYPICAL USB APPLICATION) MAX1922 toc14 VOUT 5V/div 0 FULL CURRENT LIMIT CHARGES CAPACITOR VEN 5V/div 0 RESISTOR LOAD CURRENT 0 SHORT-CIRCUIT CURRENT LIMIT 5V IIN 1A/div VOC 5A/div 1ms/div _______________________________________________________________________________________ 5 MAX1922 Typical Operating Characteristics (continued) (Circuit of Figure 2, VIN = 5V, TA = +25°C, unless otherwise noted.) 1A Current-Limited Switch for 2 USB Ports MAX1922 Pin Description PACKAGE TDFN SO NAME FUNCTION 6 1 1, 3, 9 2, 3 IN Input. p-channel MOSFET source—connect all IN pins together and bypass with a 1µF capacitor ground. 5 4 EN Active-Low Switch Enable Input. A logic-low turns on the switch. 7 5 OC 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, 8 OUT Switch Output. p-channel MOSFET drain—connect all OUT pins together and bypass with a 0.1µF capacitor to ground. — EP — GND Ground TDFN Only. Exposed paddle. Connect to the GND plane for optimum thermal dissipation. This does not remove the requirement for a proper ground. Continuous Short-Circuit Protection P IN OUT MAX1922 P OC 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 N The MAX1922 has a thermal shutdown feature. The switch turns off and the OC output goes low immediately (no overcurrent blanking) when the junction temperature exceeds +165°C. When the MAX1922 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 OC Indicator 1.24V HOT EN CONTROL CIRCUITRY GND Figure 1. Functional Diagram Detailed Description The MAX1922 p-channel MOSFET power switch limits output current to 1.4A min and 2.1A max. When the output current increases beyond the current limit (ILIMIT), the current also increases through the replica switch (IOUT / 13000). The current-limit error amplifier compares 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. 6 The MAX1922 provides an overcurrent output (OC). A 100kΩ pullup 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 hotswapping 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 overcurrent blanking timeout, the OC output asserts low. Ensure that the MAX1922 input is adequately bypassed to prevent input glitches from triggering spurious OC _______________________________________________________________________________________ 1A Current-Limited Switch for 2 USB Ports 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). INPUT IN OUT OUTPUT 0.1μF* 1μF MAX1922 100kΩ OVERCURRENT OUTPUT OC OFF ON 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)2 RON where ILIMIT is the preset current limit (2.1A max) and RON is the on-resistance of the switch (125mΩ max). When the output is short circuited, foldback-current limiting activates and the voltage drop across the switch equals the input supply voltage. The power dissipated across the switch increases, as does the die temperature. If the fault condition is not removed, the thermaloverload 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 EN GND *USB SPECIFICATIONS REQUIRE A HIGHER VALUE CAPACITOR. Figure 2. Typical Application Circuit 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. 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 inductance 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 regulator as well as local bypass capacitors, limiting overshoot. If severe ringing occurs due to large load inductance, clamp the MAX1922 output below 6V and above -0.3V. _______________________________________________________________________________________ 7 MAX1922 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 overtemperature faults and input voltage droops below the UVLO threshold will cause an immediate OC output. 1A Current-Limited Switch for 2 USB Ports MAX1922 Pin Configurations (continued) Chip Information OUT IN OUT OC GND PROCESS: BiCMOS TOP VIEW 10 9 8 7 6 Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE MAX1922 PACKAGE CODE DOCUMENT NO. 8 SO S8-5 21-0041 10 TDFN-EP T1033-1 21-0137 4 5 EN OUT 3 OUT 2 IN 1 IN + TDFN 8 _______________________________________________________________________________________ 1A Current-Limited Switch for 2 USB Ports REVISION NUMBER REVISION DATE 3 4/09 DESCRIPTION Fixed typo in UL # PAGES CHANGED 1 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. MAX1922 Revision History