Triple Switch with Autoreset Fault Blanking MAX1940 triple curren

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Triple Switch with Autoreset Fault Blanking MAX1940 triple curren

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19-2497; 7/02
Triple Switch with Autoreset Fault Blanking
MAX1940 triple current-limited switch with autoreset supplies guaranteed 500mA load channel accordance with specifications. MAX1940 operates from 5.5V input supply consumes only 60µA quiescent current when operating only standby. Selectable active-high/active-low control logic independent shutdown controls each channel provide additional flexibility. autoreset feature latches switch event short circuit, saving system power. switch reactivates upon removal shorted condition. MAX1940 provides several safety features protect port. Built-in thermal-overload protection turns switch when temperature exceeds +160°C. Accurate internal current-limiting circuitry protects input supply against both overload shortcircuit conditions. Independent open-drain fault signals (FAULTA, FAULTB, FAULTC) notify microprocessor when thermal-overload, current-limit, undervoltage lockout (UVLO), short-circuit fault occurs. 20ms fault-blanking feature enables circuit ignore momentary faults, such those caused when hot-swapping capacitive load, preventing false alarms host system. fault-blanking feature also prevents fault signals from being issued when device powers load. MAX1940 available space-saving 16-pin QSOP package operates over extended (-40°C +85°C) temperature range.
Features
Triple Switch Tiny 16-Pin QSOP Package Autoreset Feature Saves System Power Guaranteed 500mA Load Current Channel Built-In 20ms Fault-Blanking Circuitry Active-High/Active-Low Control Logic Fully Compliant Specifications 5.5V Input Voltage Range Independent Shutdown Control Independent Fault Indicator Outputs Thermal-Overload Protection Standby Current Certification Pending
MAX1940
Ordering Information
PART MAX1940EEE TEMP RANGE -40°C +85°C PIN-PACKAGE QSOP
Applications
Ports Hubs Notebook Computers Desktop Computers PDAs Palmtop Computers Docking Stations
Typical Operating Circuit
MAX1940
FAULTA FAULTB FAULTC
Configuration
VIEW
FAULTA OUTA
INPUT 5.5V
OUTA
PORT
MAX1940
OUTB FAULTB OUTC FAULTC
OUTC ACTIVE-HIGH/ACTIVE-LOW SELECTABLE PORT OUTB PORT
QSOP
Maxim Integrated Products
pricing, delivery, ordering information, please contact Maxim/Dallas Direct! 1-888-629-4642, visit Maxim's website www.maxim-ic.com.
Triple Switch with Autoreset Fault Blanking MAX1940
ABSOLUTE MAXIMUM RATINGS
IN_, ON_, OUT_, SEL, FAULT_, GND.-0.3V IN1, OUTA.-0.3V IN2, OUTB.-0.3V IN4, OUTC .-0.3V OUT_ Continuous Switch Current (per channel, internally limited).1.4A FAULT_ Current .20mA Continuous Power Dissipation +70°C) 16-Pin QSOP (derate 8.3mW/°C above +70°C).667mW Operating Temperature Range .-40°C +85°C Junction Temperature .+150°C Storage Temperature Range .-65°C +150°C Lead Temperature (soldering, 10s) .+300°C
Stresses beyond those listed under "Absolute Maximum Ratings" cause permanent damage device. These stress ratings only, functional operation device these other conditions beyond those indicated operational sections specifications implied. Exposure absolute maximum rating conditions extended periods affect device reliability.
ELECTRICAL CHARACTERISTICS
(VIN_ CIN_ 0.1µF, COUT_ 1µF, +85°C, unless otherwise noted. Typical values +25°C.)
PARAMETER Supply Voltage Range Switch On-Resistance Standby Supply Current Quiescent Supply Current IIN_ SYMBOL VIN_ +85°C, each switch switches disabled switch enabled, IOUT_ switches enabled, IOUT_ switches enabled, IOUT_ OUT_ Off-Leakage Current Undervoltage Lockout Threshold Continuous Load Current Continuous Current Limit Short-Circuit Current Limit Short-Circuit Detect Threshold Continuous Current-Limit Blanking Timeout Period Short-Circuit Blanking Timeout Period Turn-On Delay Output Rise Time Turn-Off Delay Output Fall Time Thermal-Shutdown Threshold ON_, Input High Level ON_, Input Level ON_, Input Leakage Current tRISE tOFF tFALL ILIM VIN_ VOUT_ 0.5V VOUT_ (IOUT_ pulsing) (Note From continuous current-limit condition FAULT_ asserted From short-circuit current-limit condition FAULT_ asserted ROUT_ does include rise time (from VOUT_) ROUT_ from VOUT_ ROUT_ does include fall time (from VOUT_) ROUT_ from VOUT_ 15°C hysteresis VIN_ 5.5V VIN_ 5.5V VON_ VIN_ ILKG VULVO switches disabled, VOUT_ +85°C Rising edge, hysteresis 0.35 35.0 CONDITIONS 0.02 ARMS UNITS
Triple Switch with Autoreset Fault Blanking
ELECTRICAL CHARACTERISTICS (continued)
(VIN_ CIN_ 0.1µF, COUT_ 1µF, +85°C, unless otherwise noted. Typical values +25°C.)
PARAMETER FAULT_ Output Voltage FAULT_ Output High Leakage Current OUT_ Autoreset Current OUT_ Autoreset Threshold OUT_ Autoreset Blanking Time SYMBOL CONDITIONS ISINK 1mA, VIN_ VIN_ FAULT_ 5.5V latched state, VOUT_ latched state, OUT_ rising latched state, VOUT_ 0.5V UNITS
MAX1940
ELECTRICAL CHARACTERISTICS
(VIN_ CIN_ 0.1µF, COUT_ 1µF, -40°C +85°C, unless otherwise noted.) (Note
PARAMETER Supply Voltage Range Switch On-Resistance Standby Supply Current Quiescent Supply Current OUT_ Off-Leakage Current Undervoltage Lockout Threshold Continuous Load Current Continuous Current Limit Short-Circuit Current Limit Continuous Current-Limit Blanking Timeout Period Short-Circuit Blanking Timeout Period Turn-On Delay Turn-Off Delay ON_, Input High Level ON_, Input Level ON_, Input Leakage Current FAULT_ Output Voltage FAULT_ Output High Leakage Current OUT_ Autoreset Current OUT_ Autoreset Threshold OUT_ Autoreset Blanking Time tOFF ILIM VIN_ VOUT_ 0.5V VOUT_ (IOUT_ pulsing) From continuous current-limit condition FAULT_ asserted From short-circuit current-limit condition FAULT_ asserted ROUT_ does include rise time (from VOUT_) ROUT_ does include fall time (from VOUT_) VIN_ 5.5V VIN_ 5.5V VON_ VIN_ ISINK 1mA, VIN_ VIN_ FAULT_ 5.5V latched state, VOUT_ latched state, OUT_ rising latched state, VOUT_ 0.5V IIN_ ILKG VULVO SYMBOL VIN_ Each switch switches disabled switch enabled, IOUT_ switches enabled, IOUT_ switches enabled, IOUT_ switches disabled, VOUT_ Rising edge, hysteresis 35.0 CONDITIONS UNITS
Note Short-circuit detect threshold output voltage which device transitions from short-circuit current limit continuous current limit. Note Specifications -40°C guaranteed design, production tested.
Triple Switch with Autoreset Fault Blanking MAX1940
Typical Operating Characteristics
(Circuit Figure VIN_ CIN_ 0.1µF, COUT_ 1µF, SEL, +25°C, unless otherwise noted.)
QUIESCENT SUPPLY CURRENT INPUT VOLTAGE
MAX1940 toc01
QUIESCENT SUPPLY CURRENT TEMPERATURE
SHUTDOWN SUPPLY CURRENT (µA) VIN_ 4.5V VIN_ SWITCHES ACTIVE VIN_ 5.5V
MAX1940 toc02
SHUTDOWN SUPPLY CURRENT TEMPERATURE
GND, VSEL
MAX1940 toc03
SWITCHES ACTIVE QUIESCENT SUPPLY CURRENT (µA)
QUIESCENT SUPPLY CURRENT (µA)
INPUT VOLTAGE
TEMPERATURE (°C)
TEMPERATURE (°C)
SWITCH OFF-LEAKAGE (ONE SWITCH) TEMPERATURE
MAX1940 toc04
NORMALIZED ON-RESISTANCE TEMPERATURE
MAX1940 toc05
CONTINUOUS CURRENT-LIMIT THRESHOLD TEMPERATURE
CONTINUOUS CURRENT-LIMIT THRESHOLD (mA)
MAX1940 toc06
1000 OUT_, VSEL SWITCH OFF-LEAKAGE (nA)
NORMALIZED ON-RESISTANCE
VIN_ 5.0V
VIN_ 5.5V
VIN_ 4.5V
0.01 TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
TURN-ON TIME (tON tRISE) TEMPERATURE
MAX1940 toc07
TURN-OFF TIME (tOFF tFALL) TEMPERATURE
MAX1940 toc08
FAULT-BLANKING TIME TEMPERATURE
MAX1940 toc09
ROUT_ TURN-ON TIME (ms) VIN_
VIN_ 4.5V
ROUT_ TURN-OFF TIME (ms) VIN_ 4.5V VIN_ VIN_ 5.5V
22.0 21.5 21.0 20.5 20.0 19.5 19.0 VIN_ 5.5V VIN_ 4.5V
FAULT-BLANKING TIME (ms)
VIN_
VIN_ 5.5V
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
Triple Switch with Autoreset Fault Blanking MAX1940
Typical Operating Characteristics (continued)
(Circuit Figure VIN_ CIN_ 0.1µF, COUT_ 1µF, SEL, +25°C, unless otherwise noted.)
FAULT OUTPUT VOLTAGE TEMPERATURE
MAX1940 toc10
AUTORESET CURRENT TEMPERATURE
MAX1940 toc11
AUTORESET CURRENT INPUT VOLTAGE
AUTORESET CURRENT (mA) +85°C -40°C
MAX1940 toc12
MAX1940 toc15
4.7k VIN_ VIN_ 5.5V
AUTORESET CURRENT (mA) VIN_ 4.5V VIN_ 5.5V VIN_
+25°C
FAULT OUTPUT VOLTAGE (mV)
VIN_ 4.5V
INPUT VOLTAGE
TEMPERATURE (°C)
TEMPERATURE (°C)
OVERLOAD RESPONSE INTO
MAX1940 toc13
OVERLOAD RESPONSE INTO (EXPANDED TIME SCALE)
MAX1940 toc14
SHORT-CIRCUIT RESPONSE INTO
VIN_ 5V/div VOUT_ 5V/div 10ms/div VFAULT_ 5V/div IOUT_ 1A/div VIN_ 5V/div VOUT_ 5V/div 400µs/div VFAULT_ 5V/div IOUT_ 1A/div VIN_ 5V/div VOUT_ 5V/div 10ms/div VFAULT_ 5V/div IOUT_ 1A/div
SHORT-CIRCUIT RESPONSE INTO (EXPANDED TIME SCALE)
MAX1940 toc16
SWITCH TURN-ON TIME (tON tRISE)
VSEL ROUT_ COUT_
MAX1940 toc17
SWITCH TURN-ON TIME (tON tFALL)
VSEL ROUT_ COUT_
MAX1940 toc18
VIN_ 5V/div VOUT_ 5V/div 400µs/div VFAULT_ 5V/div IIN_ 2A/div 1ms/div VON_ 5V/div VOUT_ 2V/div VON_ 5V/div VOUT_ 2V/div 1ms/div
Triple Switch with Autoreset Fault Blanking MAX1940
Typical Operating Characteristics (continued)
(Circuit Figure VIN_ CIN_ 0.1µF, COUT_ 1µF, SEL, +25°C, unless otherwise noted.)
STARTUP TIME COUT
MAX1940 toc19
STARTUP TIME COUT 330µF
MAX1940 toc20
VSEL ROUT_ COUT_
VSEL ROUT_ COUT_ 330µF
400µs/div VOUT_ 5V/div VON_ 5V/div VFAULT_ 5V/div IOUT_ 500mA/div
500mA 1ms/div VOUT_ 5V/div VON_ 5V/div VFAULT_ 5V/div IOUT_ 500mA/div
500mA
STARTUP TIME COUT 100µF
MAX1940 toc21
UNDERVOLTAGE LOCKOUT RESPONSE
MAX1940 toc22
VSEL ROUT_ COUT_ 100µF
ROUT_ COUT_
1ms/div VOUT_ 2V/div VON_ 5V/div VFAULT_ 5V/div IOUT_ 500mA/div 500mA
VIN_ 5V/div VOUT_ 5V/div
10ms/div VFAULT_ 5V/div
Triple Switch with Autoreset Fault Blanking
Description
NAME FAULTC OUTC FAULTB OUTB OUTA FAULTA FUNCTION Control Input Switch active polarity (see Table Power Input. Connect inputs together bypass with 0.1µF ceramic capacitor GND. Load conditions might require additional bulk capacitance prevent pulling down. Power Input. Connect inputs together bypass with 0.1µF ceramic capacitor GND. Load conditions might require additional bulk capacitance prevent pulling down. Power Input. Connect inputs together bypass with 0.1µF ceramic capacitor GND. Load conditions might require additional bulk capacitance prevent pulling down. Control Input Switch active polarity (see Table Power Input. Connect inputs together bypass with 0.1µF ceramic capacitor GND. Load conditions might require additional bulk capacitance prevent pulling down. Power Input. Connect inputs together bypass with 0.1µF ceramic capacitor GND. Load conditions might require additional bulk capacitance prevent pulling down. Control Input Switch active polarity (see Table Fault Indicator Output Switch Open-drain output asserts when switch enters thermal shutdown, undervoltage lockout, sustained (>20ms) current-limit short-circuit condition. Power Output Switch Bypass OUTC with ceramic capacitor. Load conditions might require additional bulk capacitance. When disabled, OUTC goes into high-impedance state. Logic Input Polarity Select. sets active polarity inputs. Connect high activehigh inputs. Connect active-low inputs. Fault Indicator Output Switch Open-drain output asserts when switch enters thermal shutdown, undervoltage lockout, enters sustained (>20ms) current-limit short-circuit condition. Power Output Switch Bypass OUTB with ceramic capacitor. Load conditions might require additional bulk capacitance. When disabled, OUTB goes into high-impedance state. Ground Power Output Switch Bypass OUTA with ceramic capacitor. Load conditions might require additional bulk capacitance. When disabled, OUTA goes into high-impedance state. Fault Indicator Output Switch Open-drain output asserts when switch enters thermal shutdown, undervoltage lockout, sustained (>20ms) current-limit short-circuit condition.
MAX1940
Triple Switch with Autoreset Fault Blanking MAX1940
CHARGE PUMP FAULTA SWITCH (EXPANDED)
ILIM OUTA THERMAL SHUTDOWN
25mA
MAX1940
FAULT LOGIC 20ms TIMERS OUTB SWITCH (SEE SWITCH UVLO 25kHz OUTC BIAS SWITCH (SEE SWITCH FAULTC FAULTB
Figure Functional Diagram
Detailed Description
MAX1940 triple current-limited power switch provides three independent switches, each with enable-control input fault indicator (see Figure logic input sets active polarity enable control inputs. fault indicators notify system when current-limit, short-circuit, undervoltage lockout, thermal-shutdown threshold exceeded. MAX1940 operates from 5.5V input supply supplies minimum output current 700mA channel. built-in current limit 0.9A (typ) limits output current event overload condition. Built-in short-circuit detection pulses output current
output voltage falls below resulting lower output current reduced power dissipation device. Independent thermal shutdown allows normal operation continue channel experiences prolonged overload short-circuit condition. Low-RON NMOS switches enable MAX1940 provide three switches space-saving 16-pin QSOP package. internal micropower charge pump generates high-side supply needed driving gates these high-side switches. Separate current-limiting thermal-shutdown circuitry permits each switch operate independently, improving system robustness.
Triple Switch with Autoreset Fault Blanking
On/Off Control Undervoltage Lockout
sets active polarity logic inputs MAX1940. Connect same voltage enable respective OUT_ switch. Connect opposite voltage disable respective output (see Table output disabled switch enters high-impedance state. MAX1940 includes UVLO circuit prevent erroneous switch operation when input voltage goes during startup brownout conditions. Input voltages less than 3.4V inhibit operation device. FAULT_ asserts during undervoltage lockout condition.
MAX1940
Table On/Off Control
OUT_ BEHAVIOR
Fault Indicators
MAX1940 provides independent open-drain fault output (FAULT_) each switch. Connect FAULT_ through 100k pullup resistor most applications. FAULT_ asserts when following conditions occur: input voltage below UVLO threshold. switch junction temperature exceeds +160°C thermal-shutdown temperature limit. switch current-limit short-circuit currentlimit mode after fault-blanking period (20ms) expires. FAULT_ output deasserts after 20ms delay once fault condition removed. Ensure that MAX1940 input bypass capacitance prevents glitches from triggering FAULT_ outputs. Limit input voltage slew rate 0.2V/µs prevent erroneous FAULT_ indications. differentiate large capacitive loads from short circuits sustained overloads, MAX1940 independent fault-blanking circuit each switch. When load transient causes device enter current limit, internal counter monitors duration fault. load faults exceeding 20ms faultblanking time, switch turns off, FAULT_ asserts low, device enters autoreset mode (see Output Fault Protection Autoreset Mode section). Only current-limit short-circuit faults blanked. Thermal overload faults input voltage drops below UVLO threshold immediately turn switch assert FAULT_ low. Fault blanking allows MAX1940 handle loads that might fully compliant with specifications. MAX1940 successfully powers loads with additional bypass capacitance and/or large startup currents while protecting upstream power source. fault reported switch brings load within 20ms blanking period. Table summary current-limit fault behavior.
Output Fault Protection Autoreset
MAX1940 senses switch output voltage selects continuous current limiting VOUT_ greater than short-circuit current limiting VOUT_ less than When VOUT_ greater than device operates continuous current-limit mode that limits output current 0.9A. When VOUT_ less than device operates short-circuit current-limit mode, sourcing 1.2A pulses load. When either fault condition persists 20ms, output turns fault flag asserted. output automatically restarts 20ms after short overload removed. MAX1940 detects short-circuit removal sourcing 25mA from output monitoring output voltage. When voltage output exceeds 0.5V 20ms, fault flag resets, output turns back 25mA current source turns off. Active loads expected have measurable current when supplied with less than 0.5V.
Thermal Shutdown
Independent thermal shutdown each channel permits normal operation switches continue while third experiences thermal fault. switch turns FAULT_ output asserts immediately when junction temperature exceeds +160°C. Thermal shutdown does utilize 20ms fault-blanking timeout period. switch turns again FAULT_ returns high when junction temperature cools +15°C. switch cycles overload condition persists, resulting pulsed output that reduces system power.
Triple Switch with Autoreset Fault Blanking MAX1940
Table Current-Limiting Fault Behavior
CONDITION MAX1940 BEHAVIOR short detected output, channel turns off, blanking timer begins. FAULT_ remains high during blanking timeout period. short persists during fault-blanking period, output pulses 0.35ARMS. short removed before 18ms short-circuit blanking timeout period, next ramped current pulse soft-starts output. FAULT_ remains high. short circuit persists after fault-blanking period, FAULT_ goes low, autoreset mode begins, output sources 25mA. output voltage rises above 0.5V 20ms, output turns FAULT_ goes high (see ShortCircuit Response Typical Operating Characteristics.)
Output Short Circuit (VOUT_
Output current regulates ILIM blanking timer turns FAULT_ remains high during blanking timeout period. Continuous current ILIM persists until either 20ms blanking period expires thermal fault occurs. Output Overload Current overcurrent persists after 20ms, FAULT_ goes low, autoreset mode enabled, output sources (VOUT_ 25mA. output voltage rises above 0.5V 20ms, output turns FAULT_ goes high (see Overload Response into Typical Operating Characteristics.) Thermal Fault +160°C) junction temperature +160°C immediately asserts FAULT_ (the blanking timeout period does apply thermal faults) turns switch. When junction cools 15°C, thermal fault cleared FAULT_ goes high. Note that other fault conditions present when thermal fault clears, those fault states take effect.
Applications Information
Input Power Supply Capacitance
Connect inputs together externally. powers internal control circuitry charge pump each switch. Bypass with 0.1µF ceramic capacitor. When driving inductive loads operating from inductive sources, which occur when MAX1940 powered long leads traces, larger input bypass capacitance required prevent voltage spikes from exceeding MAX1940's absolute maximum ratings during short-circuit events.
cables, which might inductive component load. This inductance causes output voltage port oscillate during load step. MAX1940 drives inductive loads, avoid exceeding device's absolute maximum ratings. Usually, load inductance relatively small, MAX1940's input includes substantial bulk capacitance from upstream regulator well local bypass capacitors, limiting overshoot. severe ringing occurs because large load inductance, clamp MAX1940 outputs below above -0.3V.
Turn-On Turn-Off Behavior
MAX1940's slow turn-on turn-off minimizes load transients upstream power source. Under fault conditions, outputs MAX1940 turn rapidly provide maximum safety upstream power source downstream devices. Internal blocks shut down minimize supply current when three channels off.
Output Capacitor
Bypass OUT_ with ceramic capacitor local decoupling. Additional bulk capacitance 470µF) reduces output-voltage transients under dynamic load conditions. Using output capacitors greater than 470µF might assert FAULT_ current limit cannot charge output capacitor within 20ms fault-blanking period. addition bulk capacitance, small-value (0.1µF greater) ceramic capacitors improve output's resilience electrostatic discharge (ESD).
Layout Thermal Dissipation
Keep traces short possible reduce effect undesirable parasitic inductance optimize switch response time output short-circuit conditions. Place input output capacitors more than from device leads. Connect OUT_
Driving Inductive Loads
wide variety devices (mice, keyboards, cameras, printers) typically connect port with
Triple Switch with Autoreset Fault Blanking
active switch dissipates little power with minimal change package temperature. Calculate power dissipation this condition follows:
100k
MAX1940
MAX1940
O.1µF OUTC OUTB OUTA FAULTA FAULTB FAULTC
100k 100k
INPUT 5.5V
PORT 1µF*
PORT 1µF*
(IOUT_)2 normal operating current (IOUT_ 0.5A) maximum on-resistance switch (135m), power dissipation (0.5A)2 0.135 34mW switch. worst-case power dissipation occurs when output current just below current-limit threshold (1.2A max) with output voltage greater than this case, power dissipated each switch voltage drop across switch multiplied current limit: ILIM (VIN VOUT) input output, maximum power dissipation switch 1.2A 4.8W Because package power dissipation 667mW, MAX1940 temperature exceeds +160°C thermal shutdown threshold, switch output shuts down until junction temperature cools +15°C. duty cycle period strong functions ambient temperature board layout (see Thermal Shutdown section). output current exceeds current-limit threshold, output voltage pulled below short-circuit detect threshold, MAX1940 enters fault state after 20ms, which point autoreset mode enabled 25mA sourced output. input, OUT_ short-circuited GND, autoreset mode active, power dissipation follows: 0.025A 0.125W
PORT 1µF*
*USB APPLICATIONS REQUIRE ADDITIONAL BULK CAPACITANCE
Figure Typical Application Circuit
power with short traces. Wide power planes provide superior heat dissipation well.
Chip Information
TRANSISTOR COUNT: 4259 PROCESS: BiCMOS
Triple Switch with Autoreset Fault Blanking MAX1940
Package Information
(The package drawing(s) this data sheet reflect most current specifications. latest package outline information, www.maxim-ic.com/packages.)
QSOP.EPS
Maxim cannot assume responsibility circuitry other than circuitry entirely embodied Maxim product. circuit patent licenses implied. Maxim reserves right change circuitry specifications without notice time.
_Maxim Integrated Products, Gabriel Drive, Sunnyvale, 94086 408-737-7600 2002 Maxim Integrated Products Printed registered trademark Maxim Integrated Products.

Triple Switch with Autoreset Fault Blanking MAX1940 triple curren

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