19-3128; Rev 0; 6/04 Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset The MAX1558/MAX1558H are dual, current-limited switches with autoreset for USB applications. Autoreset latches the switch off if it is shorted for more than 20ms, saving system power. The shorted output is then tested to determine when the short is removed to automatically restart the channel. Each channel delivers up to 1.2A and meets all IEC specifications for USB ports. Low quiescent supply current (45µA) and standby current (3µA) conserve battery power in portable applications. The MAX1558/MAX1558H safety features ensure that the USB port is protected. Built-in thermal-overload protection limits power dissipation and junction temperature. Accurate, programmable current-limiting circuitry protects the input supply against both overload and short-circuit conditions. 20ms fault blanking enables the circuit to ignore transient faults, such as those caused when hot swapping a capacitive load, preventing false alarms to the host system. The MAX1558/MAX1558H also feature reverse-current protection circuitry to block current flow from the output to the input when the switches are off. The MAX1558/MAX1558H are available in space-saving 3mm x 3mm, 10-pin TDFN packages. The MAX1558 is enabled with an active-low signal, and the MAX1558H is enabled with an active-high signal. Features ♦ 55mΩ Switch Resistance ♦ Tiny 10-Pin, 3mm x 3mm TDFN Package ♦ 14% Accurate Current Limit ♦ Autorestart when Fault is Removed ♦ Programmable Current Up to 1.2A ♦ Thermal-Overload Protection ♦ Built-In 20ms Fault Blanking ♦ Compliant to All USB Specifications ♦ 2.7V to 5.5V Supply Range ♦ Independent-Output Fault Indicators ♦ Block Reverse Current when Disabled ♦ 15kV ESD Protection (with Capacitor) ♦ UL Listing Pending Ordering Information TEMP RANGE PINPACKAGE MAX1558ETB -40°C to +85°C 10 TDFN (3mm x 3mm) AAR MAX1558HETB -40°C to +85°C 10 TDFN (3mm x 3mm) AAS PART Applications USB Ports and Hubs TOP MARK Notebook Computers and Desktops Typical Operating Circuit PDAs and Palmtop Computers Docking Stations Pin Configuration INPUT 2.7V TO 5.5V INA ONA ONA INB ONB ONB OUTA USB PORT A OUTB USB PORT B TOP VIEW MAX1558 INA 1 10 OUTA ONA (ONA) 2 ISET 3 FLTA 9 FLTA MAX1558 (MAX1558H) 8 GND ONB (ONB) 4 7 FLTB INB 5 6 OUTB FLTB ISET GND TDFN 3mm x 3mm ________________________________________________________________ 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 MAX1558/MAX1558H General Description MAX1558/MAX1558H Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset ABSOLUTE MAXIMUM RATINGS IN_, ON_, OUT_, ISET, FLT_ to GND........................-0.3V to +6V IN_ to OUT_ (when disabled) (Note 1) ........................-6V to +6V IN_ to OUT_ (when enabled) (Note 2) ............-1.6A to +1.6ARMS FLT_ Sink Current................................................................20mA Continuous Power Dissipation (TA = +70°C) 10-Pin TDFN 3mm x 3mm (derate 24.4mW/°C above +70°C) .............................1952mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+160°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Note 1: Reverse current (current from OUT_ to IN_) is blocked when disabled. Note 2: 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 MAX1558/MAX1558H are disabled, the switch turns off and reverse current is internally blocked. 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 (VINA = VINB = 5V, V ONA = V ONB = 0V (MAX1558), VONA = VONB = 5V (MAX1558H), RISET = 26kΩ to GND, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 3) PARAMETER SYMBOL CONDITIONS Supply Voltage Range Switch On-Resistance MIN TYP 2.75 RON VIN_ = 5V, TA = +25°C 55 VIN_ = 3.3V, TA = +25°C 64 VIN_ = 4.4V, TA = 0°C to +85°C MAX UNITS 5.50 V 75 mΩ 105 Standby Supply Current Both switches disabled 3 6 µA Quiescent Supply Current Both switches enabled 45 75 µA OUT_ Off-Leakage Current Switches disabled VOUTA = VOUTB = 0V 0.03 10 VOUTA = VOUTB = 5V 0.03 Reverse Leakage Current VIN_ = 0V, VOUTA = VOUTB = 5V, both switches disabled Undervoltage-Lockout Threshold Rising edge, 3% hysteresis 2.3 Continuous Load Current RISET = 26kΩ 1.2 Current-Limit Threshold VIN_ - VOUT_ = 0.5V Peak Short-Circuit Current Limit RMS Short-Circuit Current Limit VUVLO 0.03 ISHORT ISHORT VOUT_ = 0V (IOUT_ pulsing) VOUT_ = 0V (IOUT_ pulsing) 2.5 µA µA 2.7 V A RISET = 26kΩ 1.20 1.4 RISET = 39kΩ 0.80 0.925 1.05 RISET = 60kΩ 0.50 0.6 0.70 RISET = 26kΩ 1.45 2.0 2.60 RISET = 39kΩ 1.40 RISET = 60kΩ 0.90 RISET = 26kΩ 0.55 RISET = 39kΩ 0.37 RISET = 60kΩ 0.23 1.60 A A(PEAK) ARMS Short-Circuit Continuous CurrentLimit Transition Threshold (Note 4) Fault-Blanking Timeout Period From ILIMIT condition to 50% of V FLT_ 8 20 40 ms Turn-On Delay ROUT_ = 10Ω, COUT_ = 1µF, does not include rise time (from ON asserted to VOUT_ = 10% VIN_) 0.5 1.4 4.0 ms 2 tON 1 _______________________________________________________________________________________ V Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset (VINA = VINB = 5V, V ONA = V ONB = 0V (MAX1558), VONA = VONB = 5V (MAX1558H), RISET = 26kΩ to GND, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 3) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Output Rise Time tRISE COUT_ = 1µF, ROUT_ = 10Ω, (from 10% to 90% of VOUT_) 4 Turn-Off Delay from ON tOFF ROUT_ = 10Ω, COUT_ = 1µF, does not include rise time (from ON deasserted to VOUT_ = 90% VIN_) 100 Output Fall Time tFALL COUT_ = 1µF, ROUT_ = 10Ω (from 90% to 10% of VOUT_) 3 ms +160 °C Thermal-Shutdown Threshold 10°C hysteresis ONA/ONB Logic Input High Voltage VIH VIN_ = 2.7V to 4.0V 1.6 VIN_ 4.0V to 5.5V 2.0 ONA/ONB Logic Input Low Voltage VIL ms 1000 µs V VIN_ = 2.7V to 4.0V 0.6 VIN_ = 4.0V to 5.5V 0.8 Logic Input Current VON_ = 0V or VIN_ -1 FLT_ Output Low Voltage ISINK = 1mA FLT_ Output High Leakage Current VIN_ = V FLT_ = 5.5V Autorestart Current In latched-off state, VOUT_ = 0V 10 Autorestart Threshold In latched-off state, rising 0.4 Autorestart Delay In latched-off state, VOUT_ > 1V 8 20 V +1 µA 0.4 V 1 µA 25 50 mA 0.5 0.6 V 40 ms ELECTRICAL CHARACTERISTICS (VINA = VINB = 5V, V ONA = V ONB = 0V (MAX1558), VONA = VONB = 5V (MAX1558H), RISET = 26kΩ to GND, TA = -40°C to +85°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS Supply Voltage Range Switch On-Resistance MIN 2.7 RON TYP MAX UNITS 5.5 V VIN_ = 5V, TA = +25°C 75 VIN_ = 4.4V, TA = 0°C to +85°C 105 mΩ Standby Supply Current Both switches disabled 6 µA Quiescent Supply Current Both switches enabled 75 µA 10 µA 2.7 V OUT_ Off-Leakage Current Undervoltage-Lockout Threshold Switches disabled, VOUTA = VOUTB = 0V Rising edge, 3% hysteresis 2.3 Continuous Load Current RISET = 26kΩ 1.2 Current-Limit Threshold VIN_ - VOUT_ = 0.5V Peak Short-Circuit Current Limit VOUT_ = 0V (IOUT_ pulsing) Fault-Blanking Timeout Period VUVLO ISHORT A RISET = 26kΩ 1.20 1.60 RISET = 39kΩ 0.80 1.05 RISET = 60kΩ 0.50 0.70 RISET = 26kΩ 1.45 2.60 A(PEAK) 8 40 ms From ILIMIT condition to 50% of V FLT_ A _______________________________________________________________________________________ 3 MAX1558/MAX1558H ELECTRICAL CHARACTERISTICS (continued) ELECTRICAL CHARACTERISTICS (continued) (VINA = VINB = 5V, V ONA = V ONB = 0V (MAX1558), VONA = VONB = 5V (MAX1558H), RISET = 26kΩ to GND, TA = -40°C to +85°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN Turn-On Delay tON ROUT_ = 10Ω, COUT_ = 1µF, does not include rise time (from ON asserted to VOUT_ = 10% VIN_) Turn-Off Delay from ON tOFF ROUT_ = 10Ω, COUT_ = 1µF, does not include rise time (from ON deasserted to VOUT_ = 90% VIN_) ONA/ONB Logic Input High Voltage VIH ONA/ONB Logic Input Low Voltage VIL TYP 0.5 VIN_ = 2.7V to 4.0V 1.6 VIN_ = 4.0V to 5.5V 2.0 MAX UNITS 4.0 ms 1000 µs V VIN_ = 2.7V to 4.0V 0.6 VIN_ = 4.0V to 5.5V 0.8 Logic Input Current VON_ = 0V or VIN_ FLT_ Output Low Voltage ISINK = 1mA FLT_ Output High Leakage Current VIN_ = V FLT_ = 5.5V Autorestart Current In latched-off state, VOUT_ = 0V Autorestart Threshold In latched-off state, rising Autorestart Delay In latched-off state, VOUT_ > 1V -1 V +1 µA 0.4 V 1 µA 10 50 mA 0.4 0.6 V 8 40 ms Note 3: Specifications from 0°C to -40°C are guaranteed by design but not 100% tested. Note 4: The output voltage at which the device transitions from short-circuit current limit to continuous current limit. See the OutputCurrent Fault Protection section. Typical Operating Characteristics (VINA = VINB = 5V, V ONA = V ONB = 0V (MAX1558), VONA = VONB= 5V (MAX1558H), RISET = 26kΩ to GND. Typical values are at TA = +25°C, unless otherwise noted.) QUIESCENT SUPPLY CURRENT vs. SUPPLY VOLTAGE 1.3 1.2 1.1 1.0 0.9 0.8 0.7 50 40 30 20 50 MAX1558/58H toc03 1.4 MAX1558/58H toc02 1.5 QUIESCENT CURRENT vs. TEMPERATURE 60 QUIESCENT CURRENT (µA) MAX1558/58H toc01 1.6 VIN_ = 5.5V QUIESCENT CURRENT (µA) CURRENT-LIMIT PROGRAM vs. RISET CURRENT LIMIT (A) MAX1558/MAX1558H Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset 45 VIN_ = 5V 40 VIN_ = 4.5V 35 10 0.6 0.5 0 24 28 32 36 40 44 RISET (kΩ) 4 48 52 56 60 30 0 1 2 3 4 SUPPLY VOLTAGE (V) 5 6 -40 -15 10 35 TEMPERATURE (°C) _______________________________________________________________________________________ 60 85 Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset SWITCH OFF-LEAKAGE CURRENT vs. TEMPERATURE 2.5 2.0 1.5 1.0 0.5 -15 10 35 60 1 0.1 -40 85 -15 10 35 60 0 1 2 3 4 5 CONTINUOUS CURRENT-LIMIT THRESHOLD vs. TEMPERATURE TURN-ON TIME vs. TEMPERATURE (tON + tRISE) 1.44 8 1.43 7 TURN-ON TIME (ms) 1.42 1.41 1.40 1.39 1.38 -15 10 35 60 VIN_ = 4.5V 6 5 VIN_ = 5.5V VIN_ = 5V 4 1.37 1.36 1.35 0.50 3 -40 85 -15 10 35 60 85 -40 -15 10 35 60 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) TURN-OFF TIME vs. TEMPERATURE (tOFF + tFALL) FAULT-BLANKING TIME vs. TEMPERATURE FAULT OUTPUT LOW VOLTAGE vs. TEMPERATURE 3.00 VIN_ = 5V VIN_ = 4.5V 2.50 VIN_ = 4.5V 23 22 VIN_ = 5V 21 VIN_ = 5.5V 2.25 2.00 20 -15 10 35 TEMPERATURE (°C) 60 85 250 VIN_ = 4.5V 225 85 MAX1558/58H toc12 24 275 FAULT OUTPUT LOW VOLTAGE (mV) 3.25 MAX1558/58H toc11 VIN_ = 5.5V 3.50 25 FAULT-BLANKING TIME (ms) MAX1558/58H toc10 4.00 6 MAX1558/58H toc09 1.45 MAX1558/58H toc08 MAX1558/58H toc07 0.75 -40 0.1 85 NORMALIZED ON-RESISTANCE vs. TEMPERATURE 1.00 2.75 1 OUTPUT VOLTAGE (V) 1.25 3.75 10 TEMPERATURE (°C) 1.50 -40 100 TEMPERATURE (°C) CONTINUOUS CURRENT-LIMIT THRESHOLD (A) -40 NORMALIZED RON (Ω) 10 0.01 0 TURN-OFF TIME (ms) 100 ON_ = IN_ (MAX1558) ON_ = GND (MAX1558H) MAX1558/58H toc06 3.0 1000 MAX1558/58H toc05 ON_ = VIN_ (MAX1558) ON_ = GND (MAX1558H) SWITCH OFF-LEAKAGE CURRENT (nA) SHUTDOWN CURRENT (µA) 3.5 MAX1558/58H toc04 4.0 OFF REVERSE-BLOCKING LEAKAGE CURRENT vs. OUTPUT VOLTAGE OFF REVERSE-BLOCKING LEAKAGE CURRRENT (nA) SHUTDOWN CURRENT vs. TEMPERATURE 200 VIN_ = 5V 175 VIN_ = 5.5V 150 125 100 -40 -25 -10 5 20 35 50 TEMPERATURE (°C) 65 80 -40 -15 10 35 60 85 TEMPERATURE (°C) _______________________________________________________________________________________ 5 MAX1558/MAX1558H Typical Operating Characteristics (continued) (VINA = VINB = 5V, V ONA = V ONB = 0V (MAX1558), VONA = VONB= 5V (MAX1558H), RISET = 26kΩ to GND. Typical values are at TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VINA = VINB = 5V, V ONA = V ONB = 0V (MAX1558), VONA = VONB= 5V (MAX1558H), RISET = 26kΩ to GND. Typical values are at TA = +25°C, unless otherwise noted.) AUTORESET CURRENT vs. INPUT VOLTAGE AUTORESET CURRENT vs. TEMPERATURE 36 34 32 30 28 VIN_ = 5V VIN_ = 4.5V 26 24 40 MAX1558/58H toc14 VIN_ = 5.5V AUTORESET CURRENT (mA) 38 MAX1558/58H toc13 40 AUTORESET CURRENT (mA) MAX1558/MAX1558H Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset TA = -40°C 35 30 TA = +85°C 25 TA = +25°C 22 20 20 -40 -15 10 35 60 3.0 85 3.5 4.0 4.5 5.0 5.5 6.0 VIN (V) TEMPERATURE (°C) SHORT-CIRCUIT RESPONSE INTO 0Ω OVERLOAD RESPONSE INTO 2.5Ω MAX1558/58H toc16 MAX1558/58H toc15 VIN 5V VIN SWITCH ON 5V/div SHORT APPLIED OUT_ 0 VOUT 5V/div 0 FLT_ SHORT REMOVED 5V/div 0 AUTORESTART 5V/div 0 5A/div 0 FLTA_ IOUT_ 1A/div 0 5V/div 0 IOUT_ 20ms/div 20ms/div SWITCH TURN-ON TIME SWITCH TURN-OFF TIME MAX1558/58H toc17 MAX1558/58H toc18 2V/div ON_ 2V/div ON_ 0 0 2V/div OUT_ 0 2V/div OUT_ 0 2.0ms/div 6 1.0ms/div _______________________________________________________________________________________ Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset PIN NAME FUNCTION 1 INA 2 ONA *(ONA) Control Input for Switch A. Can be driven higher than IN_ without damage. A logic low turns switch A on for the MAX1558. A logic high turns switch A on for the MAX1558H. 3 ISET Current-Limit Adjust for Both Channels. Connect a resistor between 26kΩ to 60kΩ from ISET to ground to program the current limit. See Setting the Current Limit in the Applications Information section. 4 ONB *(ONB) Control Input for Switch B. Can be driven higher than IN_ without damage. A logic low turns switch B on for the MAX1558. A logic high turns switch B on for the MAX1558H. 5 INB 6 OUTB Power Output for Switch B. Connect a 1µF capacitor from OUTB to ground. The load condition may require additional bulk capacitance. 7 FLTB 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. 8 GND Ground 9 FLTA 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. 10 OUTA Power Output for Switch A. Connect a 1µF capacitor from OUTA to ground. The load condition may require additional bulk capacitance. — PAD Power Input for OUTA. Connect INA and INB 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. Power Input for OUTB. Connect INB and INA 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. Exposed Pad, Internally Connected to GND. Connect exposed pad to a large copper trace for maximum power dissipation. *( ) are for the MAX1558H only. Detailed Description The MAX1558/MAX1558H are dual current-limited switches designed for USB applications. They have two independent switches, each with its own enable control input and autoreset function. Each switch has an errorflag output to notify the USB controller when currentlimit, short-circuit, undervoltage-lockout, or thermalshutdown conditions occur (Figure 2). The MAX1558/ MAX1558H operate from a 2.7V to 5.5V supply. Each output can supply up to 1.2A. Current limit for both channels is set with one external resistor. The MAX1558/MAX1558H have independent thermal shutdown for each switch in the event of a prolonged overload. An autoreset function monitors the output and automatically turns the switch on when the overload is removed. Separate current limiting and thermal-shutdown circuits permit each switch to operate independently, improving system robustness. 0.1µF INPUT 2.7V TO 5.5V INA ONA ONA INB ONB ONB OUTA 100kΩ 1µF* USB PORT A MAX1558 FLTA OUTB 100kΩ 1µF* USB PORT B FLTB ISET GND *USB APPLICATIONS MAY REQUIRE ADDITIONAL BULK CAPACITANCE Figure 1. Typical Application Circuit _______________________________________________________________________________________ 7 MAX1558/MAX1558H Pin Description MAX1558/MAX1558H Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset INA FLTA INA ONA CHARGE PUMP ONA ILIMA BIAS OUTA THERMAL SHUTDOWN UVLO 30mA FAULT LOGIC REF GND 30mA OSC 25kHz TIMER 20ms OUTB ONB CHARGE PUMP ONB ILIMB INB INB 0.6V PROGRAM ILIMA PROGRAM ILIMB FLTB MAX1558 ISET Figure 2. Functional Diagram 8 _______________________________________________________________________________________ Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset The MAX1558/MAX1558H include a UVLO circuit to prevent erroneous switch operation when the input voltage is low during startup and brownout conditions. Operation is inhibited when VIN_ is less than 2.5V. Output-Current Fault Protection The current limit for both switch outputs is programmed by a resistor between 26kΩ and 60kΩ connected from ISET to ground. See the Current-Limit Program Level vs. RISET curve in the Typical Operating Characteristics and Setting the Current Limit in the Applications Information section. The MAX1558 reduces the gate drive to the MOSFET switch when the programmed current-limit value is reached. If the current-limit program value is reached, the part reduces gate drive to regulate at the current limit. If the current limit persists for 20ms (typ), the output turns off and the fault flag is set until the fault is removed, as detected by the autoreset circuit. When the the output drops below 1V (typ), the current limit is set 30% above the programmed level and pulsed. This lowers the RMS current for a short-circuit condition, which reduces system load current and power dissipation. If a short circuit persists for 20ms, the output turns off and the fault flag is set. The autoreset circuit automatically restarts the part if the fault is removed. Fault Blanking The MAX1558/MAX1558H switches can reach current limit in normal operation when powering up or driving heavy capacitive loads. To differentiate these conditions from short circuits or sustained overloads, the MAX1558/MAX1558H have independent fault-blanking circuits in each switch. When a load transient causes the device to enter the current limit, an internal counter monitors the duration of the fault. For load faults exceeding the 20ms fault-blanking time, the offending switch turns off, the corresponding FLT_ signal asserts low, and that channel enters autoreset mode (see the Autoreset Mode section). Only current-limit and shortcircuit faults are blanked. Thermal-overload faults and input-voltage drops below the UVLO threshold immediately cause the switch to turn off and FLT_ to assert low. Fault blanking allows the MAX1558 to handle USB loads that may not be fully compliant with 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. Autoreset Mode If an output fault is detected for more than the 20ms blanking time, the output latches off and the FLT_ output goes low. The MAX1558/MAX1558H then source 30mA to the faulted output and monitor the output voltage to determine when the overload is removed. If the voltage on the output rises above 0.5V for more than 20ms, the fault resets and the output turns on. The MAX1558 can also be reset from fault manually by toggling ON_ (ON_ for the MAX1558H) for that channel. Reverse Current Blocking The USB specification does not allow an output device to source current back into the USB port. However, the MAX1558/MAX1558H are designed to safely power noncompliant devices. When disabled, each output is switched to a high-impedance state, blocking reversecurrent flow from the output back to the input. However, during normal operation with the device enabled, the MAX1558/MAX1558H are bidirectional switches. Thermal Shutdown The MAX1558/MAX1558H feature 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 FLT_ output goes low immediately; fault blanking does not occur during thermal limit. When the junction cools by 10°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. Fault Indicators The MAX1558/MAX1558H provide an open-drain fault output (FLT_) for each switch. For most applications, connect FLT_ to IN_ through a 100kΩ pullup resistor. FLT_ 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 20ms fault-blanking period is exceeded. • The switch is in autoreset mode. After the fault condition is removed, the FLT_ output deasserts after a 20ms delay. Ensure that the MAX1558/MAX1558H have adequate input bypass capacitance to prevent glitches from triggering FLT_ outputs. Glitches that cause the input supply to drop below 2.5V may cause the undervoltage lockout to trigger, turning the outputs off and asserting the FLT signals. _______________________________________________________________________________________ 9 MAX1558/MAX1558H Undervoltage Lockout and Input Voltage Requirements MAX1558/MAX1558H Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset Applications Information Setting the Current Limit A resistor from ISET to ground programs the currentlimit value for both outputs. Use a resistor between 26kΩ and 86kΩ to set the current limit according to the formula: ILIM(TYPICAL) = 36400 / RISET (Amps) Do not use RISET values below 26kΩ because the maximum current rating of the device may be exceeded. RISET values larger than 60kΩ are not recommended and do not provide a lower limit current than 500mA. If the output drops below 1V (typ), the MAX1558 shifts to a short-circuit current-limit threshold that is 30% above the programmed level given by the ILIM(TYPICAL) formula. If the short-circuit threshold is exceeded, the switch shuts off immediately (no 20ms delay) and ramps the current back up in approximately 3ms. If the short persists and the current ramps all the way up to the short-circuit limit again, the switch again turns off. If the short still persists, the output pulses this way for 20ms, at which time the switch turns off and autoreset mode begins. 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 MAX1558/MAX1558H are capable of driving inductive loads, but avoid exceeding the devices’ absolute maximum ratings. Usually the load inductance is relatively small, and the MAX1558/MAX1558Hs’ 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 MAX1558/MAX1558Hs’ output below +6V and above -0.3V. Turn-On and Turn-Off Behavior In the absence of faults, the MAX1558/MAX1558Hs’ internal switches turn on and off slowly under the control of the ON_ inputs. Transition times for both edges are approximately 4ms. The slow charge-pump 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. Input Capacitor Layout and Thermal Dissipation INA and INB provide the power for all control and charge-pump circuitry and must be connected together externally. 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. When driving inductive loads, a larger capacitance prevents voltage spikes from exceeding the MAX1558/ MAX1558Hs’ absolute maximum ratings. 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 Output Capacitor Place a 1µF or greater capacitor at each output for noise immunity. When starting up into very large capacitive loads, the switch may pulse the output current at the short-circuit current-limit program level until the output voltage rises above 1V. Then, the capacitor continues to charge at the full, continuous current-limit program level. 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 500µF 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). 10 For the maximum operating current (IOUT_ = 1.2A) and the maximum on-resistance of the switch (125mΩ), the power dissipation is: P = (1.2A)2 x 0.125Ω = 180mW per switch The worst-case power dissipation occurs when the switch is in current limit and the output is greater than 1V. The instantaneous power dissipated in each switch is the voltage drop across the switch multiplied by the current limit. The fault-blanking circuit turns the output off if the fault persists for 20ms, while the autoreset circuit can turn it back on after 20ms in the off state. Thus, the average worst-case power is approximately 50% of the instantaneous value. P = 0.5 x (ILIM) x (VIN_ - VOUT_) ______________________________________________________________________________________ Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset P = 0.5 x (1.5A) x (5V - 1V) = 3W Since the package power dissipation is limited to 1952mW, the MAX1558/MAX1558H die temperature exceeds the thermal-shutdown threshold and the switch turns off. After the die temperature cools by 10°C, the switch turns on again. If the fault-overload condition continues, the switch cycles on and off with a duty cycle and period that is a function of the ambient temperature and PC board layout. Chip Information TRANSISTOR COUNT: 2932 PROCESS: BiCMOS A short across the output for more than 20ms places the part in autoreset mode. With VIN_ = 5V and an autoreset test current of 30mA, the power dissipation for a short-circuited output is given by: P = (30mA) x 5V = 0.15W ______________________________________________________________________________________ 11 MAX1558/MAX1558H For a 5V input and 1V output, the maximum possible power dissipation per switch is: 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.) 6, 8, &10L, DFN THIN.EPS MAX1558/MAX1558H Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset D N PIN 1 INDEX AREA E E2 DETAIL A CL CL L A L e e PACKAGE OUTLINE, 6, 8, 10 & 14L, TDFN, EXPOSED PAD, 3x3x0.80 mm 21-0137 NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY F 1 2 COMMON DIMENSIONS SYMBOL A MIN. 0.70 0.80 D 2.90 3.10 2.90 3.10 0.00 0.05 E A1 L k MAX. 0.40 0.20 0.25 MIN. A2 0.20 REF. PACKAGE VARIATIONS PKG. CODE N D2 E2 e JEDEC SPEC b T633-1 6 1.50±0.10 2.30±0.10 0.95 BSC MO229 / WEEA 0.40±0.05 1.90 REF T833-1 8 1.50±0.10 2.30±0.10 0.65 BSC MO229 / WEEC 0.30±0.05 1.95 REF 2.00 REF [(N/2)-1] x e T1033-1 10 1.50±0.10 2.30±0.10 0.50 BSC MO229 / WEED-3 0.25±0.05 T1433-1 14 1.70±0.10 2.30±0.10 0.40 BSC ---- 0.20±0.03 2.40 REF T1433-2 14 1.70±0.10 2.30±0.10 0.40 BSC ---- 0.20±0.03 2.40 REF PACKAGE OUTLINE, 6, 8, 10 & 14L, TDFN, EXPOSED PAD, 3x3x0.80 mm 21-0137 F 2 2 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. 12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.