19-1903; Rev 3; 10/03 Dual USB Switch with Fault Blanking and Autoreset Applications Features ♦ Dual USB Switch in Tiny 10-Pin µMAX Package ♦ Autoreset Feature Saves Power ♦ Guaranteed 720mA Load per Channel ♦ Built-In 20ms Fault Blanking ♦ Compliant to USB Specification ♦ Blocks Reverse Current in Shutdown (MAX1823A/MAX1823B) ♦ 4V to 5.5V Input Voltage Range ♦ Independent Shutdown Control (MAX1823/MAX1823A—Active Low) (MAX1823B/MAX1823H—Active High) ♦ Independent FAULT Indicator Outputs ♦ Thermal-Overload Protection ♦ 50µA Quiescent Current (Both Switches On) ♦ 3µA Standby Current ♦ UL Recognized Ordering Information PART TEMP RANGE PIN-PACKAGE MAX1823EUB -40°C to +85°C 10 µMAX MAX1823AEUB -40°C to +85°C 10 µMAX MAX1823BEUB -40°C to +85°C 10 µMAX MAX1823HEUB -40°C to +85°C 10 µMAX USB Ports and Hubs Notebook and Desktop Computers Typical Operating Circuit PDAs and Palmtop Computers Docking Stations INA OUTA USB PORT A OUTB USB PORT B IN Pin Configuration INPUT 4V TO 5.5V INB MAX1823 MAX1823A TOP VIEW *(ONA) ONA 1 INA 2 IN 3 INB 4 10 FAULTA MAX1823 MAX1823A MAX1823B MAX1823H *(ONB) ONB 5 FAULTA 9 OUTA 8 GND 7 OUTB ONA ONA 6 FAULTB ONB ONB FAULTB GND µMAX *( ) ARE FOR MAX1823B/MAX1823H. ________________________________________________________________ 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 MAX1823/MAX1823A/MAX1823B/MAX1823H General Description The MAX1823 is a dual, current-limited switch with autoreset specifically made for USB applications. The autoreset feature latches the switch off if the output is shorted, saving system power. The switch reactivates when the short circuit is removed. Each channel is guaranteed to supply 720mA and meet USB specifications. Low quiescent supply current (50µA) and standby current (3µA) conserve battery power in portable applications. The MAX1823 has multiple safety features to ensure that the USB port is protected. Built-in thermal-overload protection limits power dissipation and junction temperature. Accurate internal current-limiting circuitry protects the input supply against both overload and short-circuit conditions. Independent fault signals (FAULTA and FAULTB) notify the microprocessor (µP) when a thermal-overload, current-limit, undervoltagelockout (UVLO), or short-circuit fault occurs. A 20ms fault-blanking feature ignores momentary faults, such as those caused when hot swapping a capacitive load, preventing false alarms to the host system. The MAX1823A/MAX1823B also block reverse current (current from OUT_ to IN_) while in shutdown. The MAX1823 is available in a space-saving 10-pin µMAX package. The MAX1823/MAX1823A are enabled with an active-low signal, and the MAX1823B/MAX1823H are enabled with an active-high signal. For a single version of this device, refer to the MAX1946 data sheet. For a triple version, refer to the MAX1940 data sheet. MAX1823/MAX1823A/MAX1823B/MAX1823H Dual USB Switch with Fault Blanking and Autoreset ABSOLUTE MAXIMUM RATINGS IN, INA, INB, ONA, ONB, ONA, ONB OUTA, OUTB to GND ...........................................-0.3V to +6V FAULTA, FAULTB to GND..........................-0.3V to (VIN_ + 0.3V) MAX1823/MAX1823H, INA, IN to OUTA; INB, IN to OUTB ...................................................-0.3V to +6V MAX1823A/MAX1823B, INA, IN to OUTA; INB, IN to OUTB (when disabled, Note 3)...............-6V to +6V INA, IN to OUTA; INB, IN to OUTB (when enabled, Note 4)..............................-1.5A to +1.5ARMS FAULTA, FAULTB Current .................................................20mA 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 Junction Temperature ......................................................+150°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 (Circuit of Figure 1, VIN = VINA = VINB = 5V, ONA = ONB = GND (MAX1823/MAX1823A), ONA = ONB = IN (MAX1823B/MAX1823H), TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS Supply Voltage Range Switch On-Resistance MIN TYP 4.0 RON Standby Supply Current Quiescent Supply Current MAX UNITS 5.5 V TA = +25°C, each switch, MAX1823/MAX1823H 75 105 TA = +25°C, each switch, MAX1823A/MAX1823B 90 120 mΩ TA = 0°C to +85°C, each switch, MAX1823/MAX1823H 135 TA = 0°C to +85°C, each switch, MAX1823A/MAX1823B 165 ON_ = IN_ (MAX1823/MAX1823A), ON_ = GND (MAX1823B/MAX1823H) 3 10 IOUTA = IOUTB = 0A, one channel on 40 80 IOUTA = IOUTB = 0A, both channels on 50 100 0.02 1.00 ON_ = IN_ (MAX1823/MAX1823A), ON_ = GND (MAX1823B/MAX1823H), VOUTA = VOUTB = 0V, TA = +25oC ON_ = IN_ (MAX1823/MAX1823A), ON_ = GND (MAX1823B/MAX1823H), VOUTA = VOUTB = 0V, TA = 0oC to +85oC VUVLO Rising edge, 3% hysteresis Continuous Load Current Continuous Current Limit Short-Circuit Current Limit 2 µA µA OUT_ Off-Leakage Current Undervoltage-Lockout Threshold µA 3.0 0.02 10.00 3.4 3.8 720 ILIM ISHORT V mA VIN - VOUT_ = 0.5V 0.72 0.90 1.20 A VOUT_ = 0V (IOUT pulsing) 0.8 1.2 1.6 APEAK VOUT_ = 0V (IOUT pulsing) 0.35 _______________________________________________________________________________________ ARMS Dual USB Switch with Fault Blanking and Autoreset (Circuit of Figure 1, VIN = VINA = VINB = 5V, ONA = ONB = GND (MAX1823/MAX1823A), ONA = ONB = IN (MAX1823B/MAX1823H), TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX Short-Circuit Detect Threshold (Note 1) Continuous Current-Limit Blanking Timeout Period From continuous current-limit condition to FAULT_ assertion 10 20 35 ms Short-Circuit Blanking Timeout Period From short-circuit current-limit condition to FAULT_ assertion 7.5 18 35.0 ms MAX1823/MAX1823H 0.5 1.2 4.0 MAX1823A/MAX1823B 0.3 0.8 3.0 Turn-On Delay tON Output Rise Time tRISE Turn-Off Delay from ON Output Fall Time ROUT_ = 10kΩ, does not include rise time 1 UNITS V ms ROUT_ = 10Ω, from 10% to 90% of VOUT_ 2.5 ROUT_ = 10Ω, does not include fall time (from ON_ (MAX1823) or ON_ (MAX1823H) deasserted to VOUT = 90% of VIN_) 0.8 ms 3.0 ms tOFF tFALL ROUT_ = 10Ω, does not include fall time (from ON_ (MAX1823A) or ON_ (MAX1823B) deasserted to VOUT = 90% of VIN_) 0.1 ROUT_ = 10Ω, from 90% to 10% of VOUT_ (MAX1823/MAX1823H) 2.5 ROUT_ = 10Ω, from 90% to 10% of VOUT_ (MAX1823A/MAX1823B) 2.8 3.0 ms Thermal-Shutdown Threshold 15oC hysteresis Logic Input High Voltage VIN_ = 4V to 5.5V Logic Input Low Voltage VIN_ = 4V to 5.5V Logic Input Current ON_ = GND or IN_ (MAX1823/MAX1823A), ON_ = GND or IN_ (MAX1823B/MAX1823H) FAULT_ Output Low Voltage FAULT_ Output High Leakage Current o +160 2 C V 0.8 V +1 µA ISINK = 1mA, VIN_ = 4V 0.4 V VIN_ = V FAULT_ = 5.5V 1 µA mA -1 Autoreset OUT_ Current In latched-off state, VOUT_ = 0V 10 30 45 Autoreset Threshold In latched-off state, rising 0.4 0.5 0.6 V Autoreset Blanking Time In latched-off state, VOUT_ > 0.5V 10 20 35 ms _______________________________________________________________________________________ 3 MAX1823/MAX1823A/MAX1823B/MAX1823H ELECTRICAL CHARACTERISTICS (continued) MAX1823/MAX1823A/MAX1823B/MAX1823H Dual USB Switch with Fault Blanking and Autoreset ELECTRICAL CHARACTERISTICS (Circuit of Figure 1, VIN = VIN_ = VON_ = 5V (MAX1823B/MAX1823H); VIN = VIN_ = 5V, ON_ = GND (MAX1823/MAX1823A), TA = -40°C to +85°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS Supply Voltage Range Switch On-Resistance MIN TYP 4.0 RON Standby Supply Current MAX UNITS 5.5 V Each switch, MAX1823/MAX1823H 135 Each switch, MAX1823A/MAX1823B 165 ON_ = IN_ (MAX1823/MAX1823A), ON_ = GND (MAX1823B/MAX1823H) 10 IOUTA = IOUTB = 0A, one channel on 80 OUT_ Off-Leakage Current VUVLO IOUTA = IOUTB = 0A, both channels on 100 ON_ = IN_ (MAX1823/MAX1823A), ON_ = GND (MAX1823B/MAX1823H), VOUTA = VOUTB = 0V 10 Rising edge, 3% hysteresis Continuous Load Current Continuous Current Limit Current Limit into Short Circuit µA µA Quiescent Supply Current Undervoltage-Lockout Threshold mΩ 3.0 3.8 720 ILIM V mA VIN_ - VOUT_ = 0.5V 0.72 1.20 A VOUT_ = 0V (IOUT pulsing) 0.8 1.6 APEAK Continuous Current-Limit Blanking Timeout Period From continuous current-limit condition to FAULT_ assertion 10 35 ms Short-Circuit Blanking Timeout Period From short-circuit current-limit condition to FAULT_ assertion 7.5 35.0 ms MAX1823/MAX1823H 0.5 4.0 MAX1823A/MAX1823B 0.3 3.0 Turn-On Delay Turn-Off Delay from ON 4 ISHORT µA tON tOFF ROUT_ = 10kΩ, does not include rise time ms ROUT_ = 10Ω, does not include fall time (from ON_ (MAX1823/MAX1823A) or ON_ (MAX1823B/MAX1823H) deasserted to VOUT_ = 90% VIN_) _______________________________________________________________________________________ 3 ms Dual USB Switch with Fault Blanking and Autoreset (Circuit of Figure 1, VIN = VIN_ = VON_ = 5V (MAX1823B/MAX1823H); VIN = VIN_ = 5V, ON_ = GND (MAX1823/MAX1823A), TA = -40°C to +85°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS Logic Input High Voltage VIN_= 4V to 5.5V Logic Input Low Voltage VIN_= 4V to 5.5V MIN TYP MAX UNITS 0.8 V 2 V Logic Input Current V ON_ = 0V or VIN_ +1 µA FAULT_ Output Low Voltage ISINK = 1mA, VIN_ = 4V -1 0.4 V FAULT_ Output High Leakage Current VIN_ = V FAULT_ = 5.5V 1 µA Autoreset OUT_Current In latched-off state, VOUT_ = 0V 10 50 mA Autoreset Threshold In latched-off state, rising 0.4 0.6 V Autoreset Blanking Time In latched-off state, VOUT_ > 0.5V 10 35 ms Note 1: The output voltage at which the device transitions from short-circuit current limit to continuous current limit. Note 2: Specifications to -40°C are guaranteed by design, not production tested. Note 3: Reverse current (current from OUT_ to IN_) is blocked when disabled. Note 4: Forward current (current from IN_ to OUT_) is internally limited. Reverse current, from OUT_ to IN_, is not limited when the device is enabled and must be kept below 1.5ARMS to prevent permanent device damage. When the MAX1823A/MAX1823B are disabled, the switch turns off and reverse current is internally blocked. Typical Operating Characteristics (Circuit of Figure 1, VIN = VINA = VINB = 5V, ON_ = GND (MAX1823/MAX1823A), ON_ = IN_ (MAX1823B/MAX1823H), TA = +25°C, unless otherwise noted.) QUIESCENT CURRENT vs. TEMPERATURE QUIESCENT CURRENT (µA) 42 36 30 24 18 12 VIN_ = 5.5V 53 51 VIN_ = 5V 49 VIN_ = 4.5V 47 3.5 MAX1823 toc03 48 MAX1823 toc02 54 QUIESCENT CURRENT (µA) 55 MAX1823 toc01 60 SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE SHUTDOWN SUPPLY CURRENT (µA) QUIESCENT CURRENT vs. INPUT VOLTAGE ON_ = IN_ (MAX1823/MAX1823A) ON_ = GND (MAX1823B/MAX1823H) 3.3 3.1 2.9 2.7 6 0 45 0 1 2 3 4 INPUT VOLTAGE (V) 5 6 2.5 -40 -15 10 35 TEMPERATURE (°C) 60 85 -40 -15 10 35 60 85 TEMPERATURE (°C) _______________________________________________________________________________________ 5 MAX1823/MAX1823A/MAX1823B/MAX1823H ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (continued) (Circuit of Figure 1, VIN = VINA = VINB = 5V, ON_ = GND (MAX1823/MAX1823A), ON_ = IN_ (MAX1823B/MAX1823H), TA = +25°C, unless otherwise noted.) SWITCH OFF-LEAKAGE vs. TEMPERATURE NORMALIZED RON 1.25 10 1 1.00 0.75 0.01 35 60 85 -40 -15 TEMPERATURE (°C) 10 35 60 3.6 VIN_ = 5V 3.4 MAX1823 toc06 -40 85 -15 VIN_ = 5V 10 35 60 85 FAULT-BLANKING TIME vs. TEMPERATURE MAX1823 toc08 3.3 VIN_ = 5.5V 3.1 2.9 22.0 2.7 VIN_ = 5.5V 21.8 VIN_ = 4.5V 21.6 21.4 VIN_ = 5V VIN_ = 5.5V 21.2 VIN_ = 4.5V 2.5 3.0 -15 VIN_ = 4.5V 910 TEMPERATURE (°C) 3.5 TURN-OFF TIME (ms) VIN_ = 4.5V 10 35 60 21.0 -40 85 -15 10 35 60 85 -40 -15 10 35 60 85 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) FAULT_ OUTPUT LOW VOLTAGE vs. TEMPERATURE AUTORESET CURRENT vs. TEMPERATURE (MAX1823/MAX1823H) AUTORESET CURRENT vs. TEMPERATURE (MAX1823A/MAX1823B) 0.200 VIN_ = 4.5V 0.175 0.150 VIN_ = 5.5V VIN_ = 5.5V 35 30 25 MAX1823 toc12 VIN_ = 5V 36 AUTORESET CURRENT (mA) 0.225 40 MAX1823 toc11 IFAULT_ = 1mA AUTORESET CURRENT (mA) 0.250 MAX1823 toc10 -40 VIN_ = 5V TURN-OFF TIME vs. TEMPERATURE (tOFF + tFALL) MAX1823 toc07 4.0 3.2 920 TEMPERATURE (°C) TURN-ON TIME vs. TEMPERATURE (tON + tRISE) 3.8 VIN_ = 5.5V MAX1823 toc09 10 FAULT-BLANKING TIME (ms) -15 930 900 0.50 -40 TURN-ON TIME (ms) 940 CONTINUOUS CURRENT LIMIT (mA) MAX 1823 toc05 MAX1823 toc04 100 SWITCH OFF-LEAKAGE (nA) 1.50 0.1 VIN_ = 5.5V 34 VIN_ = 5V 32 30 20 0.125 VIN_ = 5V VIN_ = 4.5V 0.100 VIN_ = 4.5V 28 15 -40 -15 10 35 TEMPERATURE (°C) 6 CONTINUOUS CURRENT-LIMIT THRESHOLD vs. TEMPERATURE NORMALIZED RON vs. TEMPERATURE 1000 FAULT_ OUTPUT LOW VOLTAGE (V) MAX1823/MAX1823A/MAX1823B/MAX1823H Dual USB Switch with Fault Blanking and Autoreset 60 85 -40 -15 10 35 TEMPERATURE (°C) 60 85 -40 -15 10 35 TEMPERATURE (°C) _______________________________________________________________________________________ 60 85 Dual USB Switch with Fault Blanking and Autoreset AUTORESET CURRENT vs. INPUT VOLTAGE (MAX1823/MAX1823H) OVERLOAD RESPONSE INTO 2.5Ω (MAX1823/MAX1823H) AUTORESET CURRENT vs. INPUT VOLTAGE (MAX1823A/MAX1823B) MAX1823 toc15 37 AUTORESET CURRENT (mA) 40 TA = +25°C 30 20 TA = +85°C 10 MAX1823 toc14 TA = -40°C AUTORESET CURRENT (mA) 39 MAX1823 toc13 50 5V B 0 C 0 35 TA = +85°C 33 TA = +25°C 31 29 27 0 A D TA = -40°C 0 25 3.6 4.4 5.2 6.0 3.6 INPUT VOLTAGE (V) 4.4 5.2 6.0 A: VIN_, 5V/div B: VOUTA, 5V/div INPUT VOLTAGE (V) OVERLOAD RESPONSE INTO 2.5Ω (EXPANDED TIME SCALE) OVERLOAD RESPONSE INTO 2.5Ω (MAX1823A/MAX1823B ONLY) SHORT-CIRCUIT RESPONSE INTO 0Ω (MAX1823/MAX1823H) MAX1823 toc17 MAX1823 toc16 A 5V B 0 MAX1823 toc18 5V A B 10ms/div C: VFAULTA, 5V/div D: IOUTA, 1A/div 0 5V A B 0 C C C 0 0 0 D D 0 0 A: VIN_, 5V/div B: VOUTA, 5V/div 10ms/div C: VFAULTA, 5V/div D: IOUTA, 1A/div A: VIN_, 5V/div B: VOUTA, 5V/div SHORT-CIRCUIT RESPONSE INTO 0Ω (MAX1823A/MAX1823B) 500µs/div C: VFAULTA, 5V/div D: IOUTA, 1A/div 0 A: VIN_, 5V/div B: VOUTA, 5V/div 10ms/div C: VFAULTA, 5V/div D: IOUTA, 1A/div SWITCH TURN-ON TIME (MAX1823/MAX1823A) SHORT-CIRCUIT RESPONSE INTO 0Ω (EXPANDED TIME SCALE) MAX1823 toc19 MAX1823 toc21 MAX1823 toc20 5V A D A 5V A 0 B 0 C B 0 C 5V D 0 0 B D 0 A: VIN_, 5V/div B: VOUTA, 5V/div 10ms/div C: VFAULTA, 5V/div D: IOUTA, 2A/div A: VIN_, 5V/div B: VOUTA, 5V/div 500µs/div C: VFAULTA, 5V/div D: IOUTA, 2A/div 0 A: VONA, 5V/div B: VOUTA, 2V/div 1ms/div _______________________________________________________________________________________ 7 MAX1823/MAX1823A/MAX1823B/MAX1823H Typical Operating Characteristics (continued) (Circuit of Figure 1, VIN = VINA = VINB = 5V, ON_ = GND (MAX1823/MAX1823A), ON_ = IN_ (MAX1823B/MAX1823H), TA = +25°C, unless otherwise noted.) MAX1823/MAX1823A/MAX1823B/MAX1823H Dual USB Switch with Fault Blanking and Autoreset Typical Operating Characteristics (continued) (Circuit of Figure 1, VIN = VINA = VINB = 5V, ON_ = GND (MAX1823/MAX1823A), ON_ = IN_ (MAX1823B/MAX1823H), TA = +25°C, unless otherwise noted.) STARTUP TIME (TYPICAL USB APPLICATION) SWITCH TURN-OFF TIME (tOFF + tFALL) MAX1823 toc23 MAX1823 toc22 A 0 A 0 B 5V C 0 B D 0 0 1ms/div A: VONA, 5V/div B: VFAULTA, 5V/div A: VONA, 5V/div B: VOUTA, 2V/div 500µs/div C: VOUTA, 2V/div D : IOUTA, 0.5A/div Pin Description PIN NAME FUNCTION 1 ONA *(ONA) Control Input for Switch A. Can be driven higher than IN_ without damage. A logic low turns switch A on for the MAX1823/MAX1823A, and a logic high turns switch A on for the MAX1823B/MAX1823H. 2, 3, 4 INA, IN, INB Power Input. Connect all IN_ pins together, and bypass with a 0.1µF capacitor to ground. Load conditions may require additional bulk capacitance to prevent the input from being pulled down. 5 ONB *(ONB) Control Input for Switch B. Can be driven higher than IN_ without damage. A logic low turns switch B on for the MAX1823/MAX1823A, and a logic high turns switch B on for the MAX1823B/MAX1823H. 6 FAULTB Fault-Indicator Output for Switch B. This open-drain output goes low when switch B is in thermal shutdown or UVLO or in a sustained (>20ms) current-limit or short-circuit condition. 7 OUTB Power Output for Switch B. Connect a 1µF capacitor from OUTB to ground. Load condition may require additional bulk capacitance. 8 GND Ground 9 OUTA Power Output for Switch A. Connect a 1µF capacitor from OUTA to ground. Load condition may require additional bulk capacitance. 10 FAULTA Fault-Indicator Output for Switch A. This open-drain output goes low when switch A is in thermal shutdown or UVLO or in a sustained (>20ms) current-limit or short-circuit condition. *() are for the MAX1823B/MAX1823H only. 8 _______________________________________________________________________________________ Dual USB Switch with Fault Blanking and Autoreset The MAX1823 is a dual, current-limited switch designed for USB applications. It has two independent switches, each with its own enable control input and autoreset function. Each switch has an error-flag output to notify the USB controller when the current-limit, short-circuit, undervoltage-lockout, or thermal-shutdown threshold is reached (Figure 2). The MAX1823 operates from a 4V to 5.5V input voltage range and guarantees a minimum 720mA output current. A built-in 0.9A current limit limits the current in the event of a heavy-overload condition. The MAX1823 has independent thermal shutdown for each switch in the event of a prolonged overload or short-circuit condition. The autoreset function monitors the overload and automatically turns the switch on when the overload is removed. Use of low-RON NMOS switches enables the MAX1823 to provide two switches in the ultra-small 10-pin µMAX package. An internal micropower charge pump generates the high-side supply needed for driving the gates of these high-side switches. Separate current-limiting and thermal-shutdown circuits permit each switch to operate independently, improving system robustness. Undervoltage-Lockout and Input-Voltage Requirements The MAX1823 includes a UVLO circuit to prevent erroneous switch operation when the input voltage goes low during startup and brownout conditions. Operation is inhibited when VIN_ is less than 3.4V. Output Fault Protection The MAX1823 senses the switch output voltage and selects continuous current limiting when VOUT is greater than 1V or short-circuit current limiting when VOUT is less than 1V. When VOUT is greater than 1V, the device operates in a continuous current-limit mode that sets the output current limit to 0.9A. When VOUT is less than 1V, the device operates in short-circuit current-limit mode, sourcing 0.35ARMS current pulses to the load. Thermal Shutdown The MAX1823 features independent thermal shutdown for each switch channel, allowing one switch to deliver power even if the other switch has a fault condition. When the junction temperature exceeds +160°C, the switch turns off and the FAULT_ output goes low immediately; fault blanking does not occur during thermal limit. When the junction cools by 15°C, the switch turns on again. If the fault overload condition continues, the switch cycles on and off, resulting in a pulsed output, saving battery power. Reverse Current Blocking The USB specification does not allow an output device to source current back into the USB port. However, the MAX1823A/MAX1823B are designed to safely power noncompliant devices. When disabled, each output is switched to a high-impedance state, blocking reverse current flow from the output back to the input. However, during normal operation with the device enabled, the MAX1823A/MAX1823B are bidirectional switches. Fault Indicators The MAX1823 provides an open-drain fault output (FAULT_) for each switch. For most applications, connect FAULT_ to IN_ through a 100kΩ pullup resistor. FAULT_ goes low when any of the following conditions occur: • The input voltage is below the UVLO threshold. • The switch junction temperature exceeds the +160°C thermal-shutdown temperature limit. • The switch is in current-limit or short-circuit limit mode after the fault-blanking period is exceeded. • The switch is in autoreset mode. IN INPUT 4V TO 5.5V USB PORT A 1µF* INB 0.1µF Autoreset Mode If an output fault is detected for more than the 20ms blanking time, the output latches off, the FAULT_ output goes low, and a 25mA current is forced at the output. If the voltage on the output exceeds 0.5V for 20ms, the fault resets, the 25mA current source shuts down, and the output turns on. The device monitors the output voltage so that a short-circuit condition can be detected. Active loads are not expected to have measurable currents when the supply is below 0.5V. The MAX1823/MAX1823A can also be reset from fault manually by toggling ON_ (ON_ for the MAX1823B/MAX1823H) for that channel. OUTA INA 100kΩ 100kΩ MAX1823 FAULTA OUTB FAULTB ONA ONB ONA ONB USB PORT B 1µF* GND * USB APPLICATIONS MAY REQUIRE ADDITIONAL BULK CAPACITANCE. Figure 1. Typical Application Circuit _______________________________________________________________________________________ 9 MAX1823/MAX1823A/MAX1823B/MAX1823H Detailed Description MAX1823/MAX1823A/MAX1823B/MAX1823H Dual USB Switch with Fault Blanking and Autoreset After the fault condition is removed, the FAULT_ output deasserts after a 20ms delay. Ensure that the MAX1823 has adequate input bypass capacitance to prevent glitches from triggering FAULT_ outputs. Input glitches greater than 0.2V/µs may cause erroneous FAULT_ indications. Behavior During Current Limit and Fault Blanking The MAX1823 limits switch current in three ways. When ON_ is deasserted (high for MAX1823/MAX1823A, low for MAX1823B/MAX1823H), the switch is off and leakage dominates the residual output current. When ON_ is asserted (low for MAX1823/MAX1823A, high for MAX1823B/MAX1823H), the switch supplies a continuous output current of at least 720mA. When the output current exceeds the 0.9A threshold, the MAX1823 limits the current depending on the output voltage. For V OUT_ greater than 1V (current-limit mode), the MAX1823 regulates the output current to 0.9A. For VOUT_ less than 1V (short-circuit mode), the MAX1823 pulses the switch, decreasing the current to 0.35ARMS (Table 1). Note that a thermal overload may result from either of these high-current conditions. The MAX1823 switches may enter current limit in normal operation when powering up or driving heavy capacitive loads. To differentiate these conditions from short circuits or sustained overloads that may damage the device, the MAX1823 has an independent faultblanking circuit in each switch. When a load transient causes the device to enter current limit, an internal counter starts to monitor the duration of the fault. For load faults exceeding 20ms fault-blanking time, the switch turns off, the FAULT_ signal asserts low, and the device enters autoreset mode (see the Autoreset Mode section). Only current-limit and short-circuit faults are blanked. Thermal-overload faults and input voltage drops below the UVLO threshold immediately cause the switch to turn off and FAULT_ to assert low. INA FAULTA INA ONA CHARGE PUMP *(ONA) ILIM BIAS OUTA UVLO THERMAL SHUTDOWN FAULT LOGIC REF 4V TO 5.5V IN_ OSC 25kHz 0.1µF 1µF 25mA TIMER 20ms GND 25mA OUTB MAX1823/MAX1823A MAX1823B/MAX1823H *(ONB) ONB 1µF ILIM CHARGE PUMP INB INB *( ) ARE FOR THE MAX1823B/MAX1823H. FAULTB Figure 2. Functional Diagram 10 ______________________________________________________________________________________ Dual USB Switch with Fault Blanking and Autoreset CONDITION MAX1823 BEHAVIOR • • Output short circuit (VOUT < 1V) • • • Output overload current (VOUT > 1V) • • • Thermal fault (TJ > +160°C) • An output short circuit ramps the current to ISHORT in 2ms to 3ms, the switch shuts off, the blanking timer turns on, FAULT_ stays high, and the output current pulses at 0.35ARMS. Removing the short circuit before the 15ms short-circuit blanking timeout period allows the next ramped current pulse to soft-start the output. The FAULT_ flag stays high. A short circuit exceeding 15ms to 20ms forces FAULT_ low at 20ms, enables autoreset mode, and sources 25mA at the output. An output voltage above 0.5V for 20ms resets the switch, turns on the output, and forces FAULT_ high. An output overload regulates the current at ILIM (0.9A), and FAULT_ stays high until the overload is removed, a thermal fault occurs, or the 20ms continuous current-limit timeout period is reached. An overcurrent condition still present at 20ms forces FAULT_ low, enables autoreset, and sources 25mA at the output. An output voltage above 0.5V for 20ms resets the switch, turns on the output, and forces FAULT_ high. A junction temperature of +160°C immediately forces FAULT_ low (the blanking timer does not apply to thermal faults) and turns off the switch. The junction cooling 15°C removes the thermal fault condition, enables autoreset mode, and sources 25mA at the output. FAULT_ remains low while a thermal fault condition is present. An output voltage above 0.5V for 20ms resets the switch, turns on the output, and forces FAULT_ high. Fault blanking allows the MAX1823 to handle USB loads that may not be fully compliant with the USB specifications. USB loads with additional bypass capacitance and/or large startup currents can be successfully powered even while protecting the upstream power source. No fault is indicated if the switch is able to bring up the load within the 20ms blanking period. Applications Information Input Power Source IN, INA, and INB provide the power for all control and charge-pump circuitry. All three IN_ pins must be connected together externally. The input-voltage slew rate should be less than 0.2V/µs to prevent erroneous FAULT_ indications. This condition should not occur under normal USB applications. Input Capacitor Connect a capacitor from IN_ to ground to limit the input voltage drop during momentary output short-circuit conditions. A 0.1µF ceramic capacitor is required for local decoupling; higher capacitor values further reduce the voltage drop at the input (see the Typical Application Circuit (Figure 1)). When driving inductive loads, a larger capacitance prevents voltage spikes from exceeding the MAX1823’s absolute maximum ratings. Output Capacitor Place a 1µF or greater capacitor at each output for noise immunity. When starting up into very large capacitive loads, the switch pulses the output current at 0.35ARMS until the output voltage rises above 1V, then the capacitor continues to charge at the full 0.9A current limit. There is no limit to the output capacitor size, but to prevent a startup fault assertion, the capacitor must charge up within the fault-blanking delay period. Typically, starting up into a 330µF or smaller capacitor does not trigger a fault output. In addition to bulk capacitance, small-value (0.1µF or greater) ceramic capacitors improve the output’s resilience to electrostatic discharge (ESD). 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 MAX1823 is capable of driving inductive loads, but avoids exceeding the device’s absolute maximum ratings. Usually the load inductance is relatively small, and the MAX1823’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 MAX1823’s output below 6V and above -0.3V. ______________________________________________________________________________________ 11 MAX1823/MAX1823A/MAX1823B/MAX1823H Table 1. MAX1823 Current Limiting and Fault Behavior MAX1823/MAX1823A/MAX1823B/MAX1823H Dual USB Switch with Fault Blanking and Autoreset Turn-On and Turn-Off Behavior In the absence of faults, the MAX1823’s internal switches turn on and off slowly under the control of the ON_ inputs. Transition times for both edges are provided in the Electrical Characteristics table. The slow chargepump switch drive minimizes load transients on the upstream power source. Under thermal fault and UVLO, the power device turns off rapidly (100ns) to protect the power device. Layout and Thermal Dissipation To optimize the switch response time to output shortcircuit conditions, keep all traces as short as possible to reduce the effect of undesirable parasitic inductance. Place input and output capacitors no more than 5mm from device leads. 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 switch IN_ and OUT_ pins. While the switches are on, power dissipation is small, and the package temperature change is minimal. Calculate the power dissipation for this condition as follows: P = (IOUT_)2 RON For the normal operating current (IOUT_ = 0.5A), and the maximum on-resistance of the switch (135mΩ), the power dissipation is: P = (0.5A)2 x 0.135Ω = 34mW per switch For a 5V input and 1V output, the maximum power dissipation per switch is: P = (1.2A) ( 5V - 1V) = 4.8W Since the package power dissipation is only 444mW, the MAX1823 die temperature exceeds the thermalshutdown threshold, and the switch output shuts down until the junction temperature cools by 15°C. The duty cycle and period are strong functions of the ambient temperature and the PC board layout. A short circuit at the output causes the power dissipated across the switch and the junction temperature to increase. If the fault condition persists, the thermaloverload-protection circuitry activates, and the output shuts down until the junction temperature decreases by 15°C (see the Thermal Shutdown section). Since the output short-circuit current is 25mA (typ), and with VIN_ = 5V, calculate the power dissipation for a short-circuited output as follows: P = (0.025A)(5) = 0.125W Chip Information TRANSISTOR COUNT: 3227 PROCESS: BiCMOS The worst-case power dissipation occurs when the switch is in current limit and the output is greater than 1V. In this case, the power dissipated in each switch is the voltage drop across the switch multiplied by the current limit: P = (ILIM) (VIN - VOUT) 12 ______________________________________________________________________________________ Dual USB Switch with Fault Blanking and Autoreset 10LUMAX.EPS e 4X S 10 10 INCHES H ÿ 0.50±0.1 0.6±0.1 1 1 0.6±0.1 BOTTOM VIEW TOP VIEW D2 MILLIMETERS MAX DIM MIN 0.043 A 0.006 A1 0.002 A2 0.030 0.037 0.120 D1 0.116 0.118 D2 0.114 0.120 E1 0.116 0.118 E2 0.114 0.199 H 0.187 L 0.0157 0.0275 L1 0.037 REF b 0.007 0.0106 e 0.0197 BSC c 0.0035 0.0078 0.0196 REF S α 0∞ 6∞ MAX MIN 1.10 0.15 0.05 0.75 0.95 3.05 2.95 3.00 2.89 3.05 2.95 2.89 3.00 4.75 5.05 0.40 0.70 0.940 REF 0.177 0.270 0.500 BSC 0.090 0.200 0.498 REF 0∞ 6∞ E2 GAGE PLANE A2 c A b A1 α E1 D1 L L1 FRONT VIEW SIDE VIEW PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE, 10L uMAX/uSOP APPROVAL DOCUMENT CONTROL NO. 21-0061 REV. I 1 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 ____________________ 13 © 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX1823/MAX1823A/MAX1823B/MAX1823H 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.)