MAX1922

19-2254; Rev 3; 4/09 1A Current-Limited Switch for 2 USB Ports General Description 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. 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. PART MAX1922ESA+ MAX1922ETB+ 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 MAX1922 Ordering Information TEMP RANGE -40°C to +85°C -40°C to +85°C PINPACKAGE 8 SO 10 TDFN-EP* TOP MARK — AQQ Applications Notebook Computers USB Ports USB Hubs Docking Stations *EP = Exposed paddle. +Denotes a lead(Pb)-free/RoHS-compliant package. Pin Configurations TOP VIEW INPUT 2.7V TO 5.5V Typical Operating Circuit IN GND IN IN 1 2 8 7 OUT OUT OUTPUT MAX1922 OUT OUT OC ON OFF EN GND OC MAX1922 3 6 5 EN 4 SO 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. 1A Current-Limited Switch for 2 USB Ports MAX1922 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 OPERATING CONDITION Input Voltage POWER SWITCH Switch Static Drain-Source OnState Resistance Switch Turn-On Time Switch Turn-Off Time ENABLE INPUT (EN) EN High-Level Input Voltage EN Low-Level Input Voltage EN Input Current Startup Time CURRENT LIMIT Overload Output Current Short-Circuit Output Current SUPPLY CURRENT Supply Current, Low-Level Input Supply Current, High-Level Input Supply-Leakage Current UNDERVOLTAGE LOCKOUT Undervoltage Lockout OVERCURRENT (OC) OC Threshold OC Output Low Voltage VOL ISINK = 1mA, VIN = 3V 1.1 0.4 A V UVLO Rising edge, 100mV hysteresis 2.0 2.4 2.6 V IQ VEN = VIN = VOUT = 5.5V VEN = 0, IOUT = 0 VEN = VIN = 5.5V, VOUT = 0 Timer not running Timer running TA = +25°C TA = 0°C to +85°C 0.002 16 35 0.01 2 15 1 25 µA µA µA ILIMIT ISC Force VOUT to 4.5V OUT shorted to GND 1.4 1.75 1 2.1 1.4 A A VIH VIL VIN = 2.7V to 3.6V VIN = 3.7V to 5.5V VIN = 2.7V to 5.5V VEN = VIN or GND VIN = 5V, COUT = 150µF from EN driven low to 50% full VOUT -1 1 2.0 2.4 0.8 1 V V µA ms TA = +25°C RDS(ON) tON tOFF TA = 0°C to +85°C ILOAD = 400mA ILOAD = 400mA 3 VIN = 4.4V to 5.5V VIN = 4.4V to 5.5V VIN = 3V 72 80 6 70 100 125 150 200 20 µs µs mΩ VIN 2.7 5.5 V SYMBOL CONDITIONS MIN TYP MAX UNITS 2 _______________________________________________________________________________________ 1A Current-Limited Switch for 2 USB Ports ELECTRICAL CHARACTERISTICS (continued) (VIN = 5V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER OC Off-State Current OC Blanking Timeout Period THERMAL SHUTDOWN Thermal Shutdown Threshold 165 °C tBL SYMBOL CONDITIONS VIN = VOC = 5V From overcurrent condition to OC assertion 6 10 MIN TYP MAX 1 13 UNITS µA ms MAX1922 ELECTRICAL CHARACTERISTICS (VIN = 5V, TA = -40°C to +85°C, unless otherwise noted.) (Note 1) PARAMETER OPERATING CONDITION Input Voltage POWER SWITCH Switch Static Drain-Source On-State Resistance Switch Turn-On Time Switch Turn-Off Time ENABLE INPUT (EN) EN High-Level Input Voltage EN Low-Level Input Voltage EN Input Current CURRENT LIMIT Overload Output Current Short-Circuit Output Current SUPPLY CURRENT Supply Current, Low-Level Input Supply Current, High-Level Input Supply Leakage Current UNDERVOLTAGE LOCKOUT Undervoltage Lockout OVERCURRENT (OC) OC Threshold OC Output Low Voltage OC Off-State Current OC Blanking Timeout Period tBL VOL ISINK = 1mA, VIN = 3V VIN = VOC = 5V From overcurrent condition to OC assertion 6 1.1 0.4 1 14 A V µA ms UVLO Rising edge, 100mV hysteresis 2.0 2.9 V IQ VEN = VIN = VOUT = 5.5V VEN = GND, IOUT = 0, timer not running VEN = VIN = 5.5V, VOUT = GND 2 25 15 µA µA µA ILIMIT ISC Force VOUT to 4.5V OUT shorted to GND 1.2 2.3 1.5 A A VIH VIL VIN = 3.0V to 3.6V VIN = 3.7V to 5.5V VIN = 3.0V to 5.5V VEN = VIN or GND -1 2.0 2.4 0.8 1 V V µA RDS(ON) tON tOFF VIN = 4.4V to 5.5V VIN = 3V ILOAD = 400mA ILOAD = 400mA 1 125 150 200 20 mΩ µs µs VIN 3.0 5.5 V SYMBOL CONDITIONS MIN TYP MAX UNITS Note 1: Specifications to -40°C are guaranteed by design, not production tested. _______________________________________________________________________________________ 3 1A Current-Limited Switch for 2 USB Ports MAX1922 Typical Operating Characteristics (Circuit of Figure 2, VIN = 5V, TA = +25°C, unless otherwise noted.) QUIESCENT CURRENT vs. INPUT VOLTAGE MAX1922 toc01 QUIESCENT CURRENT vs. TEMPERATURE MAX1922 toc02 OFF SUPPLY CURRENT vs. TEMPERATURE EN = IN OUT = OPEN OFF SUPPLY CURRENT (nA) 10 MAX1922 toc03 20 18 QUIESCENT CURRENT (μA) 16 14 12 10 8 6 4 2 0 VEN = 0 IOUT = 0 18.0 IOUT = 0 17.5 QUIESCENT CURRENT (μA) 17.0 16.5 16.0 15.5 15.0 14.5 14.0 VIN = 3V VIN = 5V 100 1 0.1 0.01 -40 -15 10 35 60 85 -40 -15 TEMPERATURE (°C) 10 35 TEMPERATURE (°C) 60 85 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 INPUT VOLTAGE (V) OFF SWITCH CURRENT vs. TEMPERATURE MAX1922 toc04 NORMALIZED ON-RESISTANCE vs. TEMPERATURE MAX1922 toc05 NORMALIZED OUTPUT CURRENT vs. OUTPUT VOLTAGE ILIMIT(1.75A) MAX1922 toc06 1000 EN = IN VOUT = 0 OFF SWITCH CURRENT (nA) 100 1.4 1.3 1.2 NORMALIZED RON 1.1 1.0 0.9 0.8 0.7 IOUT = 850mA 1.2 NORMALIZED OUTPUT CURRENT 1.0 0.8 0.6 10 1 SHORT-CIRCUIT CURRENT 0.4 0.2 0 0.1 0.6 0.5 0.01 -40 -15 10 35 TEMPERATURE (°C) 60 85 0.4 -40 -15 10 35 60 85 TEMPERATURE (°C) 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 OUTPUT VOLTAGE (V) TURN-ON TIME vs. TEMPERATURE 140 120 TURN-ON TIME (μs) VIN = 3V 100 80 60 40 20 0 -40 -15 10 35 60 85 TEMPERATURE (°C) VIN = 5V IOUT = 850mA COUT = 0.1μF MAX1922 toc07 TURN-OFF TIME vs. TEMPERATURE MAX1922 toc08 OC BLANKING TIMEOUT vs. TEMPERATURE 14 OC BLANKING TIMEOUT (ms) 13 12 11 10 9 8 7 6 5 VIN = 3V OR 5V IOUT = 1.75A MAX1922 toc09 160 9.0 8.5 8.0 TURN-OFF TIME (μs) 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 -40 -15 10 35 60 VIN = 3V VIN = 5V IOUT = 850mA COUT = 0.1μF 15 85 -40 -15 10 35 60 85 TEMPERATURE (°C) TEMPERATURE (°C) 4 _______________________________________________________________________________________ 1A Current-Limited Switch for 2 USB Ports Typical Operating Characteristics (continued) (Circuit of Figure 2, VIN = 5V, TA = +25°C, unless otherwise noted.) MAX1922 CURRENT-LIMIT AND OC RESPONSE MAX1922 toc10 CURRENT-LIMIT RESPONSE MAX1922 toc11 5V 5V VIN AC-COUPLED 100mV/div VOUT, 5V/div 0 VOC, 5V/div 0 IOUT, 1A/div 0 2ms/div 0 4μs/div IOUT, 2A/div 0 5V VOUT, 5V/div VOC, 5V/div VIN AC-COUPLED 500mV/div SWITCH TURN-ON TIME MAX1922 toc12 SWITCH TURN-OFF TIME MAX1922 toc13 VOUT, 5V/div 0 VEN, 5V/div 0 VOUT, 5V/div VEN, 5V/div 0 5V VOC, 5V/div 0 5V VOC, 5V/div IOUT, 500mA/div 0 20μs/div 1μs/div IOUT, 500mA/div 0 STARTUP TIME (TYPICAL USB APPLICATION) MAX1922 toc14 0 FULL CURRENT LIMIT CHARGES CAPACITOR VOUT 5V/div VEN 5V/div 0 RESISTOR LOAD CURRENT 0 5V 1ms/div SHORT-CIRCUIT CURRENT LIMIT IIN 1A/div VOC 5A/div _______________________________________________________________________________________ 5 1A Current-Limited Switch for 2 USB Ports MAX1922 Pin Description PACKAGE TDFN 6 1, 3, 9 5 7 2, 4, 8, 10 — SO 1 2, 3 4 5 6, 7, 8 — NAME GND IN EN OC OUT EP Ground Input. p-channel MOSFET source—connect all IN pins together and bypass with a 1µF capacitor ground. Active-Low Switch Enable Input. A logic-low turns on the switch. 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. Switch Output. p-channel MOSFET drain—connect all OUT pins together and bypass with a 0.1µF capacitor to ground. TDFN Only. Exposed paddle. Connect to the GND plane for optimum thermal dissipation. This does not remove the requirement for a proper ground. FUNCTION Continuous Short-Circuit Protection IN P OUT MAX1922 OC P 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 REPLICA AMPLIFIER ON P 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. ON CURRENT-LIMIT AMPLIFIER 1.24V OC Indicator 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. 10ms TIMER 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 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 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. 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. MAX1922 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 1μF 100kΩ OVERCURRENT OUTPUT OFF ON IN OUT OUTPUT 0.1μF* MAX1922 OC EN GND 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 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. *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. _______________________________________________________________________________________ 7 1A Current-Limited Switch for 2 USB Ports MAX1922 Pin Configurations (continued) PROCESS: BiCMOS OUT OUT 10 9 8 OC IN Chip Information TOP VIEW 7 GND 6 Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE PACKAGE CODE S8-5 T1033-1 DOCUMENT NO. 21-0041 21-0137 MAX1922 8 SO 10 TDFN-EP + 1 IN 2 OUT 3 IN 4 OUT 5 EN TDFN 8 _______________________________________________________________________________________ 1A Current-Limited Switch for 2 USB Ports Revision History REVISION NUMBER 3 REVISION DATE 4/09 Fixed typo in UL # DESCRIPTION PAGES CHANGED 1 MAX1922 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.