Current-Limited Switch for Two USB Ports

Transcription

1 9-2385; Rev 2; /2 Current-Limited Switch for Two USB Ports General escription The MAX93 current-limited 7mΩ switch with built-in fault blanking provides an accurate, preset.2a to 2.3A current limit, making it ideal for dual USB applications. Its low quiescent supply current (6µA) and standby current (µa) conserve battery power in portable applications. The MAX93 operates with inputs from 2.7V to 5.5V, making it ideal for both 3V and 5V systems. The MAX93 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 current-limiting circuitry to protect the input supply against overload. The MAX93 is offered in a space-saving 8-pin SO package and operates over the extended (-4 C to +85 C) temperature range. Features Pin Compatible with TPS2 TPS23 Accurate Current Limit (.2A min, 2.3A max) 25mΩ (max) High-Side MOSFET Short-Circuit and Thermal Protection Undervoltage Lockout 6µA Quiescent Supply Current µa (max) Standby Supply Current 2.7V to 5.5V Supply Range UL Recognized: UL# E2395 MAX93 Notebook Computers USB Ports and Hubs ocking Stations Applications Ordering Information PART TEMP RANGE P-PACKAGE MAX93ESA -4 C to +85 C 8 SO Pin Configuration Typical Operating Circuit TOP VIEW PUT 2.7V TO 5.5V PUT 8 MAX MAX NC OFF SO Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/allas irect! at , or visit Maxim s website at

2 MAX93 ABSOLUTE MAXIMUM RATGS, to...-.3v to +6V to...-.3v to (V +.3V) Maximum Switch Current...2.3A (internally limited) Short Circuit to...continuous Continuous Power issipation (T A = +7 C) 8-Pin SO (derate 5.88mW/ C above +7 C)...47mW Operating Temperature Range (extended)...-4 C to +85 C Storage Temperature Range C to +5 C Lead Temperature (soldering, s)...+3 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 (V = 5V, T A = C to +85 C, unless otherwise noted. Typical values are at T A = +25 C.) PARAMETER SYMBOL CITIS M TYP MAX UNITS OPERATG CITI Input Voltage V V POWER SWITCH Switch Static rain-source On-Resistance R S() T A = +25 C V = 4.4V to 5.5V 7 T A = C to +85 C V = 4.4V to 5.5V 25 V = 3V 72 5 Switch Turn-On Time t I LOA = 4mA 8 2 µs Switch Turn-Off Time t OFF I LOA = 4mA µs ABLE PUT () V = 2.7V to 3.6V 2. High-Level Input Voltage V IH V = 3.7V to 5.5V 2.4 Low-Level Input Voltage V IL V = 2.7V to 5.5V.8 V Input Current V = V or - + µa Startup Time CURRT LIMIT V = 5V, C = 5µF from driven low to 5% full V ms Overload Output Current I LIMIT Force V to 4.5V A Short-Circuit Output Current I SC shorted to.5 A SUPPLY CURRT Supply Current, Low-Level Input V = V = V = 5.5V.2 µa Supply Current, High-Level Input I Q V =, I = Supply Leakage Current UNERVOLTAGE LOCK Timer not running 6 25 Timer running 35 V = V = 5.5V, T A = +25 C. 2 V = T A = C to +85 C 5 Undervoltage Lockout UVLO Rising edge, mv hysteresis V THERMAL SHUTOWN Thermal-Shutdown Threshold 65 C mω V µa µa 2

3 ELECTRICAL CHARACTERISTICS (V = 5V, T A = -4 C to +85 C, unless otherwise noted.) (Note ) PARAMETER SYMBOL CITIS M TYP MAX UNITS OPERATG CITI Input Voltage V V POWER SWITCH Switch Static rain-source On-Resistance V = 4.4V to 5.5V 25 R S() V = 3V 5 Switch Turn-On Time t I LOA = 4mA 2 µs Switch Turn-Off Time t OFF I LOA = 4mA 2 µs ABLE PUT () V = 3V to 3.6V 2. High-Level Input Voltage V IH V = 3.7V to 5.5V 2.4 mω V MAX93 Low-Level Input Voltage V IL V = 3V to 5.5V.8 V Input Current V = V or - + µa CURRT LIMIT Overload Output Current I LIMIT Force V to 4.5V A Short-Circuit Output Current I SC shorted to.5 A SUPPLY CURRT Supply Current, Low-Level Input V = V = V = 5.5V 2 µa Supply Current, High-Level Input I Q V =, I =, timer not running 25 µa Supply Leakage Current V = V = 5.5V, V = 5 µa UNERVOLTAGE LOCK Undervoltage Lockout UVLO Rising edge, mv hysteresis V Note : Specifications to -4 C are guaranteed by design, not production tested. (Circuit of Figure 2, V = 5V, T A = +25 C, unless otherwise noted.) QUIESCT CURRT (µa) QUIESCT CURRT vs. PUT VOLTAGE 2 V = 8 I = PUT VOLTAGE (V) MAX93 toc QUIESCT CURRT (µa) QUIESCT CURRT vs. TEMPERATURE 8. I = V = 5V V = 3V Typical Operating Characteristics MAX93 toc2 OFF SUPPLY CURRT (na). = = OP OFF SUPPLY CURRT vs. TEMPERATURE MAX93 toc3 3

4 MAX93 Typical Operating Characteristics (continued) (Circuit of Figure 2, V = 5V, T A = +25 C, unless otherwise noted.) OFF SWITCH CURRT (na). = V = OFF SWITCH CURRT vs. TEMPERATURE MAX93 toc4 NORMALIZE R NORMALIZE -RESISTANCE vs. TEMPERATURE I = 85mA MAX93 toc5 NORMALIZE PUT CURRT NORMALIZE PUT CURRT vs. PUT VOLTAGE I LIMIT (.75A) SHORT-CIRCUIT CURRT PUT VOLTAGE (V) MAX93 toc6 TURN- TIME (µs) TURN- TIME vs. TEMPERATURE I = 85mA C =.µf V = 5V V = 3V MAX93 toc7 TURN-OFF TIME (µs) TURN-OFF TIME vs. TEMPERATURE I = 85mA C =.µf V = 5V V = 3V MAX93 toc8 5V CURRT-LIMIT RESPSE MAX93 toc9 4µs/div V AC-COUPLE 5mV/div V, 5V/div I, 2A/div SWITCH TURN- TIME MAX93 toc SWITCH TURN-OFF TIME MAX93 toc STARTUP TIME (TYPICAL USB APPLICATI) MAX93 toc2 V, 5V/div V, 5V/div V, 5V/div V, 5V/div FULL CURRT LIMIT CHARGES CAPACITOR V 5V/div V 5V/div RESISTOR LOA CURRT 2µs/div I, 5mA/div µs/div I, 5mA/div SHORT-CIRCUIT CURRT LIMIT ms/div I A/div 4

5 P NAME FUNCTI Ground Pin escription 2, 3 Input. P-channel MOSFET source connect all pins together and bypass with a µf capacitor to ground. 4 Active-Low Switch Enable Input. A logic low turns on the switch. 5 NC No Connection. This pin is not internally connected and can be connected to. 6, 7, 8 Switch Output. P-channel MOSFET drain connect all pins together and bypass with a.µf capacitor to ground. MAX93 P P MAX93 Thermal Shutdown The MAX93 has a thermal shutdown feature. The switch turns off when the junction temperature exceeds +65 C. When the MAX93 cools 2 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 P CURRT-LIMIT AMPLIFIER Applications Information Input Capacitor To limit the input voltage drop during momentary output short-circuit conditions, connect a capacitor from to. A µf ceramic capacitor is adequate for most applications; however, higher capacitor values further reduce the voltage drop at the input (Figure 2)..24V Output Capacitor Connect a.µf capacitor from to. This capacitor helps to prevent inductive parasitics from pulling negative during turn-off. Figure. Functional iagram etailed escription The MAX93 P-channel MOSFET power switch limits output current to.2a (min) and 2.3A (max). When the output current increases beyond the current limit (I LIMIT ), the current also increases through the replica switch (I / 3,). The current-limit error amplifier compares the voltage to the internal.24v reference and regulates the current back to the I LIMIT (Figure ). These switches are not bidirectional. As a result, the input voltage must be higher than the output voltage. Continuous Short-Circuit Protection The MAX93 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 A continuous. Layout and Thermal issipation It is important to 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 and pins must be connected with short traces to the power bus. Wide power-bus planes provide superior heat dissipation through the MAX93 s and pins. Under normal operating conditions, the package can dissipate and channel heat away. Calculate the maximum power dissipation as follows: P = (I LIMIT ) 2 R where I LIMIT is the preset current limit (2.3A max) and R is the on-resistance of the switch (25mΩ 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 tempera- 5

6 MAX93 PUT µf.µf* MAX93 OVERCURRT PUT OFF PUT riving 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 MAX93 is capable of driving inductive loads, but avoid exceeding the device s absolute maximum ratings. Usually the load inductance is relatively small, and the MAX93 s 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 MAX93 output below 6V and above -.3V. *USB SPECIFICATIS REQUIRE A HIGHER VALUE CAPACITOR. Figure 2. Typical Application Circuit ture. If the fault condition is not removed, the thermaloverload protection circuitry activates (see the Thermal Shutdown section). Wide power-bus planes connected to and and a ground plane in contact with the device help dissipate additional heat. TRANSISTOR COUNT: 75 PROCESS: BiCMOS Chip Information 6

7 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 N E H CHES MILLIMETERS IM A A M.53.4 MAX.69. M.35. MAX B C e.5 BSC.27 BSC E H L SOICN.EPS MAX93 TOP VIEW VARIATIS: IM CHES MILLIMETERS M MAX M MAX N MS AA AB AC A C e B A FRT VIEW L SIE VIEW -8 PROPRIETARY FORMATI TITLE: PACKAGE LE,.5" SOIC APPROVAL OCUMT CTROL NO. REV. 2-4 B 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, 2 San Gabriel rive, Sunnyvale, CA Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.