MAX1838 19-2033 Rev 1 2/10 Dual USB Switch with Fault Blanking and Autoreset General Description Features The MAX1838 is a dual, current-limited USB switch with Dual USB Switch with Auxiliary Input auxiliary input supply. Each switch meets all IEC speci- Autoreset from Fault Condition fications for USB ports and is guaranteed to supply 500mA from either of two input supplies. A control pin Guaranteed 500mA Load per Channel selects the power source from either the main or auxil- Programmable Current Limits on Auxiliary Inputs iary supply. Reverse Current Protection The MAX1838 has multiple protection features, includ- ing independent thermal-shutdown on each channel to Thermal Overload Protection limit junction temperature in case of a prolonged short Built-In 20ms Fault-Blanking or overload condition. The device has accurate internal current-limit and reverse-current protection to safe- 4V to 5.5V Range guard the input supply against overload. When pow- Independent FAULT Indicator Outputs ered from the auxiliary supply, the current limit on each channel is set independently with an external resistor. An autoreset feature latches the switch off if the output is shorted, thereby saving system power. When the short is removed, the switch automatically turns back Ordering Information on. Independent fault signals (FAULTA and FAULTB) notify the microprocessor (P) that the internal current PART TEMP RANGE PIN-PACKAGE limit has been reached. A 20ms fault-blanking feature MAX1838EEE -40C to +85C 16 QSOP prevents the MAX1838 from issuing false alarms to the host during power-up or when hot-swapping into a capacitive load. The MAX1838 is available in a space-saving 16-pin QSOP. For other USB current-limited switches, refer to the MAX1693, MAX1694, MAX1812, and MAX1823. Applications Desktops Typical Operating Circuit Notebook Computers USB Ports Docking Stations Pin Configuration AUX AUXA FAULTB AUXB FAULTA TOP VIEW GND 1 16 FAULTA MAX1838 OUTB IN INA OUTB SEL 2 15 ADJA INB 10F AUXA 3 14 OUTA2 OUTA INA 4 MAX1838 13 OUTA1 SEL OUTA INB 5 12 OUTB2 ON ADJB AUXB 6 11 OUTB1 ADJA GND ON 7 10 ADJB GND 9 FAULTB 8 QSOP Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com.Dual USB Switch with Fault Blanking and Autoreset ABSOLUTE MAXIMUM RATINGS IN , AUX , ON, OUT , SEL, FAULT , Operating Temperature Range ...........................-40C to +85C ADJ to GND.........................................................-0.3V to +6V Junction Temperature......................................................+150C IN , AUX to OUTA IN , AUX to OUTB .................-6V to +6V Storage Temperature Range .............................-65C to +150C AUX to IN .................................................................-6V to +6V Lead Temperature (soldering, 10s) .................................+300C Maximum Continuous Switch Current (per channel, internally limited).............................................1.2A FAULT Current ..................................................................20mA Continuous Power Dissipation (T = +70C) A 16-Pin QSOP (derate 8.3mW/C above +70C)..........667mW 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 (V = V = 5V, ON = SEL = GND, ADJ = open, T = 0C to +85C, unless otherwise noted. Typical values are at T = IN AUX A A +25C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS V 4.0 5.5 IN Supply Voltage Range V V 4.0 5.5 AUX V = 5V, each switch 95 170 IN Switch On-Resistance R m ON V = 4V, each switch 100 IN AUX Standby Supply Current V = V 7 16 A ON AUX IN Standby Supply Current V = V 13A ON IN AUX Quiescent Supply Current V = 0V, I = 0A 66 350 A ON OUT IN Quiescent Supply Current V = 0V, I = 0A, SEL = AUX 23 300 A ON OUT OUT Off-Leakage Current V = V , V = V = 0V 0.02 10 A ON IN OUTA OUTB Reverse Leakage Current V = 5.5V, V = V = 0V 0.02 10 A OUT IN AUX Undervoltage Lockout Threshold V V or V rising edge, 3% hysteresis 3.0 3.5 3.8 V UVLO IN AUX Continuous Load Current 500 mA V - V = 0.5V, SEL = AUX 0.6 0.9 1.2 IN OUT Current-Limit Threshold I V - V = 0.5V, SEL = GND 0.6 0.9 1.2 A LIM AUX OUT R = 67k 0.09 0.225 0.36 ADJ SEL = GND, 0.3 0.48 A PEAK V = 0V R = 67k OUT ADJ (I pulsing) 0.09 A OUT RMS Short-Circuit Current Limit I SHORT 0.6 1.2 1.8 A PEAK SEL = AUX , V = 0V OUT 0.35 A RMS Continuous Current-Limit From continuous current-limit condition to 10 20 35 ms Blanking Timeout Period FAULT assertion Short-Circuit Blanking Timeout From short-circuit current-limit condition to 7.5 18 35 ms Period FAULT assertion 2 MAX1838