Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fa
|
|
|
Top Searches for this datasheet
19-1694; 4/01
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection
MAX4271/MAX4272/MAX4273 comprise complete family integrated hot-swap controllers. They allow safe insertion removal circuit cards into live backplanes. discharged filter capacitors circuit card provide impedance live backplane. High inrush currents from backplane circuit card burn connectors components, momentarily collapse backplane power supply leading system reset. This family hot-swap controllers prevents such problems regulating current preset limit when board plugged allowing system stabilize safely. After startup cycle completed, on-chip comparators provide DualSpeed/BiLevelprotection against short circuits, load glitches, overcurrent conditions. event fault condition, load disconnected. Fault recovery handled unlatching (MAX4271), autoretry (MAX4272), programmed (MAX4273) methods. MAX4271 family includes many integrated features that reduce component count design time. onboard charge pump provides gate drive lowcost, external N-FET. Integrated features like startup current regulation current glitch protection eliminate external timing resistors capacitors. Also featured open-drain status output indicate fault condition, adjustable overcurrent response time. MAX4271 (latched fault protection) MAX4272 (autoretry fault protection) come 8-pin packages. MAX4273 (full function) comes space-saving 16-pin QSOP package 16-pin package. parts specified across extended temperature range, have absolute maximum rating provide extra protection against inductive kickback during board removal.
DualSpeed/BiLevel trademark Maxim Integrated Products.
Features
Provide Safe Swap +12V Power Supplies with External Components Unique Current Regulation Architecture Minimizes N-FET Linear Mode Duration Autoretry Feature (MAX4272/MAX4273) DualSpeed/BiLevel Current Limit Protects Against Current Glitches Short Circuits Power-On RESET (MAX4273) Absolute Maximum Rating Protects Against Inductive Kickbacks During Board Removal Internal Charge Pump Generates Gate Drive External N-MOSFET Status Output Indicates Fault/Safe Condition Space-Saving 8-Pin 16-Pin QSOP Packages
MAX4271/MAX4272/MAX4273
_Applications
Base Stations RAID Remote-Access Servers Network Routers Switches ISDN
Ordering Information
PART MAX4271ESA MAX4272ESA MAX4273EEE MAX4273ESE TEMP. RANGE -40°C +85°C -40°C +85°C -40°C +85°C -40°C +85°C PIN-PACKAGE QSOP
Configurations appear data sheet.
Typical Operating Circuit
BACKPLANE REMOVABLE CARD 2.7V 13.2V RSENSE VOUT CBOARD STAT STAT CSPD SENSE GATE
MAX4271 MAX4272
CTIM CTIM
Maxim Integrated Products
free samples latest literature, visit www.maxim-ic.com phone 1-800-998-8800. small orders, phone 1-800-835-8769.
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection MAX4271/MAX4272/MAX4273
ABSOLUTE MAXIMUM RATINGS
.+15V STAT, OUTC, LLMON, AUXVCC .-0.3V +14V GATE .-0.3V (VIN 8.5V) GATE LLMON (Note 1).-1V +8.5V INC, (Note .-1V +14V CEXT .-8.5V (VIN 0.3V) CSPD, CTON, .-0.3V lower (VIN 0.3V) +12V VSENSE, RTH, CTIM GND.-0.3V (VIN 0.3V) Current into INC, (Note .±2mA Current into Other .±50mA Continuous Power Dissipation +70°C) 8-Pin (derate 5.9mW/°C above +70°C).471mW 16-Pin QSOP (derate 8.3mW/°C above +70°C).667mW 16-Pin (derate 8.7mW/°C above +70°C).696mW Operating Temperature Range .-40°C +85°C Storage Temperature Range .-65°C +150°C Lead Temperature (soldering, 10s) .+300°C
Note GATE pulled below LLMON, current must limited 2mA. Note pulled below ground. Limiting current ensures that these pins never lower than about -0.8V.
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 +2.7V +13.2V, -40°C +85°C, unless otherwise noted. Typical values +25°C.) (Note
PARAMETER POWER SUPPLIES Input Voltage Range Supply Current CURRENT CONTROL Slow Comparator Threshold Slow Comparator Response Time VSC,TH tCSPD VSENSE CSPD floating CSPD 100nF Fast Comparator Threshold VFC,TH MAX4273 only MAX4271/MAX4272 Fast Comparator Response Time SENSE Input Bias Current MOSFET DRIVER Startup Period (Notes Gate Charge Current MAX4271/MAX4272 CTIM 100nF tSTART IGATE MAX4273 CTON 100nF capacitor GATE (Note tFCD IB,SENSE 10mV overdrive, from overload condition gate discharging VSENSE +25°C TMIN TMAX +25°C TMIN TMAX +25°C TMIN TMAX 43.5 43.5 13.2 SYMBOL CONDITIONS UNITS
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection
ELECTRICAL CHARACTERISTICS (continued)
(VIN +2.7V +13.2V, -40°C +85°C, unless otherwise noted. Typical values +25°C.) (Note
PARAMETER SYMBOL CONDITIONS Time from trigger VGATE 0.1V (triggered either input slow comparator), CGATE 1000pF Time from current overload VGATE 0.1V (triggered fast comparator, during normal operation), CGATE 1000pF Voltage which internal zener clamp circuitry triggered, measured with respect (MAX4271/MAX4272), measured with respect VLLMON (MAX4273) Measured with respect VIN, IGATE 8.5µA 2.7V 2.75 UNITS
MAX4271/MAX4272/MAX4273
Slow Turn-Off Time
tSLOW,OFF
Fast Turn-Off Time
tFAST,OFF
Maximum Gate Protection Voltage
Minimum Gate Drive Voltage
During fast discharge, fast comparator fault normal operation Gate Discharge Current IGATE,DIS During startup (current regulation provided fast comparator) During normal discharge, slow comparator fault normal mode, going LLMON Overvoltage Threshold GATE Overvoltage Threshold LLMON Impedance REFERENCE (MAX4273) Output Voltage Line Regulation Load Regulation RESET COMPARATORS Threshold Voltage Hysteresis Power-Supply Rejection Ratio Propagation Delay VHYST PSRR tD,COMP 2.7V 13.2V 10mV overdrive, going positive negative, going negative going positive VREF
VREF, LINE
Startup initiated only after VLLMON less than this voltage (MAX4273) Startup initiated only after VGATE less than this voltage Impedance GND, after fault (MAX4273) load, 2.7V 13.2V, load IREF 100µA,
1.164 1.236
VREF,
LOAD
rising threshold
0.575
0.625
mV/V
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection MAX4271/MAX4272/MAX4273
ELECTRICAL CHARACTERISTICS (continued)
(VIN +2.7V +13.2V, -40°C +85°C, unless otherwise noted. Typical values +25°C.) (Note
PARAMETER Input Voltage Range Input Bias Current Pulse Width (Note DIGITAL OUTPUTS (STAT, OUTC) Output Leakage Current Output Voltage Retry Timeout Period Default Retry Timeout Period tRETRY tRETRY (default) RETRY TIMING (MAX4272, MAX4273) 100nF capacitor CTIM (Note CTIM connection VSTAT 13.2, VOUTC 13.2 ISINK IB,COMP tRESTART unlatch fault MAX4271, MAX4273 with CTIM SYMBOL CONDITIONS Input driven absolute maximum limit without false output inversion -0.1 0.001 13.2 UNITS
UNDERVOLTAGE LOCKOUT (UVLO) Threshold Hysteresis Delay VUVLO VUVLO,HYST tD,UVLO Time input voltage must exceed undervoltage lockout before startup initiated Startup initiated when this threshold exceeded 2.25 2.67
Note devices 100% tested +25°C. temperature limits guaranteed design. Note Startup period time during which slow comparator ignored fast comparator regulates sense current. measured from time brought high. Note Inferred from test with CTIM 1nF. Note current available GATE function VGATE (see Typical Operating Characteristics). Note Guaranteed design.
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection
Typical Operating Characteristics
(VIN RSENSE 100m, CBOARD 47µF, +25°C, unless otherwise noted.)
MAX4271/MAX4272/MAX4273
SUPPLY CURRENT INPUT VOLTAGE
MAX4271/3-01
SUPPLY CURRENT TEMPERATURE
SUPPLY CURRENT (mA)
MAX4271/3-02
SLOW COMPARATOR RESPONSE TIME INPUT VOLTAGE
tCSPD (µs)
MAX4271/3-03
SUPPLY CURRENT (mA) IGATE 10µA
tCSPD (ms)
CSPD 110nF TIME
CSPD TIME
TEMPERATURE (°C)
SLOW COMPARATOR THRESHOLD INPUT VOLTAGE
MAX4271/3-04
FAST COMPARATOR RESPONSE TIME OVERDRIVE VOLTAGE
MAX4271/3-05
FAST COMPARATOR RESPONSE TIME TEMPERATURE
MAX4271/3-06
51.0 50.8 50.6 50.4 VSC,TH (mV) 50.2 50.0 49.8 49.6 49.4 49.2 49.0 +85°C -40°C +25°C
RESPONSE TIME (ns)
RESPONSE TIME (ns)
1000 OVERDRIVE VOLTAGE (mV)
TEMPERATURE (°C)
FAST COMPARATOR THRESHOLD INPUT VOLTAGE
MAX4271/3-07
TIME FAST DISCHARGE GATE CGATE
EXTERNAL MOSFET DISCHARGE VGATE 0.1V
MAX4271/3-08
STARTUP PERIOD INPUT VOLTAGE
CTIM 100nF TIME
MAX4271/3-09
VFC,TH (mV) +85°C -40°C +25°C
100k TIME DISCHARGE GATE (µs) 0.01
tSTART (ms)
tSTART (µs)
CTIM TIME
1000
CGATE (nF)
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection MAX4271/MAX4272/MAX4273
Typical Operating Characteristics (continued)
(VIN RSENSE 100m, CBOARD 47µF, +25°C, unless otherwise noted.)
FAST GATE DISCHARGE CURRENT VGATE
MAX4271/3-10
GATE CHARGE CURRENT GATE VOLTAGE
MAX4271/3-11
GATE CHARGE CURRENT TEMPERATURE
VGATE
MAX4271/3-12
FAST GATE DISCHARGE CURRENT (mA)
IGATE (µA) 3.0V
IGATE (µA)
5.0V
VGATE TEMPERATURE (°C)
GATE VOLTAGE INPUT VOLTAGE
MAX4271/3-13
SLOW GATE DISCHARGE CURRENT GATE VOLTAGE
MAX4271/3-13a
TIME CHARGE GATE CGATE
EXTERNAL MOSFET TIME CHARGE GATE (ms) 0.01 0.001 0.01 VGATE VGATE
MAX4271/3-14
IGATE 10µA +85°C +25°C
IGATE (µA)
1000
VGATE
-40°C
VGATE
TRIGGERED FAULT FALLING
1000
VGATE
CGATE (nF)
FAST GATE DISCHARGE CURRENT
MAX4271/3-15
SLOW GATE DISCHARGE CURRENT TEMPERATURE
MAX4271/3-16
TIME SLOW DISCHARGE GATE CGATE
EXTERNAL MOSFET DISCHARGE VGATE 0.1V
MAX4271/3-17
FAST GATE DISCHARGE CURRENT (mA) RISING
IGATE (µA) VGATE TRIGGERED FAULT FALLING
1000 TIME DISCHARGE GATE (ms)
FALLING
0.01
0.001 0.01
1000
TEMPERATURE (°C)
CGATE (nF)
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection
Typical Operating Characteristics (continued)
(VIN RSENSE 100m, CBOARD 47µF, +25°C, unless otherwise noted.)
FAST GATE DISCHARGE CURRENT TEMPERATURE
FAST GATE DISCHARGE CURRENT (mA) TEMPERATURE (°C) 50µs/div CBOARD 470µF, RSENSE 100m, CGATE 200µs/div CBOARD 470µF, RSENSE 100m, CGATE 22nF, VGATE (2V/div) VOUT (2V/div) VGATE
MAX4271/3-18
MAX4271/MAX4272/MAX4273
MAX4271/MAX4272 TURN-OFF TIME (CBOARD 470µF)
MAX4271/3-19
MAX4271/MAX4272 TURN-OFF TIME (EXTERNAL CGATE 22nF, CBOARD 470µF)
MAX4271/3-20
VGATE 2V/div ILOAD 1A/div
ILOAD (1A/div)
VOUT 2V/div
MAX4273 TURN-OFF TIME (EXTERNAL CGATE 22nF, CBOARD 470µF)
MAX4271/3-20a
MAX4273 TURN-OFF TIME (CBOARD 470µF)
MAX4271/3-20b
COMPARATOR THRESHOLD INPUT VOLTAGE
MAX4271/3-21
0.605 ILOAD 1A/div COMPARATOR THRESHOLD
VGATE 2V/div
ILOAD 1A/div
VGATE 2V/div
0.603
RISING
0.601 FALLING 0.599
VOUT 2V/div
VOUT 2V/div
0.597
0.595 20µs/div 50µs/div
ON-COMPARATOR THRESHOLD TEMPERATURE
MAX4271/3-22
UVLO THRESHOLD VOLTAGE TEMPERATURE
MAX4271/3-26
UVLO DELAY TEMPERATURE
MAX4271/3-27
0.6100 COMPARATOR THRESHOLD 0.6075 0.6050 0.6025 0.6000 0.5975 0.5950
2.60 2.55 UVLO THRESHOLD RISING 2.50 2.45 FALLING 2.40 2.35 2.30
UVLO DELAY (ms)
TEMPERATURE (°C)
FALLING RISING
TEMPERATURE (°C) TEMPERATURE (°C)
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection MAX4271/MAX4272/MAX4273
Typical Operating Characteristics (continued)
(VIN RSENSE 100m, CBOARD 47µF, +25°C, unless otherwise noted.)
MAX4273 REFERENCE VOLTAGE INPUT VOLTAGE
MAX4271/3-29
THRESHOLD INPUT VOLTAGE
MAX4271/3-28
THRESHOLD TEMPERATURE
THRESHOLD (mV) FALLING RISING 1.2040 1.2038 REFERENCE VOLTAGE 1.2036 1.2034 1.2032 1.2030 1.2028 1.2026 1.2024 1.2022 1.2020
RISING 0.615 THRESHOLD
0.605
FALLING
0.595
0.585
0.575 INPUT VOLTAGE
TEMPERATURE (°C)
INPUT VOLTAGE
REFERENCE VOLTAGE TEMPERATURE
MAX4271/3-31
RETRY TIMEOUT PERIOD INPUT VOLTAGE
CTIM 100nF RETRY TIMEOUT (ms)
MAX4271/3-32
1.2040 1.2035 REFERENCE VOLTAGE 1.2030 1.2025 1.2020 1.2015 1.2010 1.2005 1.2000
TEMPERATURE (°C)
INPUT VOLTAGE
RETRY TIMEOUT PERIOD TEMPERATURE
MAX4271/3-33
STARTUP TIME (CBOARD 470µF)
MAX4271/3-34
RETRY PERIOD (ms)
VGATE 2V/div
ILOAD 1A/div
VOUT 2V/div
TEMPERATURE (°C)
500µs/div CBOARD 470µF, RSENSE 100m, CTIM 10nF, CGATE
MAX4271/3-30
0.625
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection
Typical Operating Characteristics (continued)
(VIN RSENSE 100m, CBOARD 47µF, +25°C, unless otherwise noted.)
STARTUP TIME (CBOARD
MAX4271/3-35
MAX4271/MAX4272/MAX4273
TURN-OFF TIME (CBOARD
MAX4271/3-37
VGATE 2V/div VGATE 2V/div
ILOAD 1A/div
VOUT 2V/div
VOUT 2V/div
100µs/div CBOARD RSENSE 100m, CTIM 10nF, CGATE
50µs/div CBOARD RSENSE 100m, CGATE
Description
MAX4271 MAX4272 MAX4273 NAME FUNCTION Current-Sense Threshold Setting Input. Connect resistor from fast comparator threshold. Bypass with 0.1µF. Connect disable both fast comparator current regulation startup. Short 200mV threshold. Fast Comparator Threshold section. Auxiliary Supply Input. Supply input short-circuit switchover. this, connect capacitor from AUXVCC GND; otherwise, leave floating. Auxiliary section. Input Voltage. Connect +2.7V +13.2V supply; absolute maximum voltage rating. Current-Sense Resistor Voltage Input. RSENSE connected from SENSE. Gate Drive Output. Connect gate external N-channel pass transistor. External Gate Capacitance Connection. Connect capacitor from CEXT GATE increase gate charging time. This goes high impedance during fast comparator fault fast discharge. Load Line Monitor. Connect source external N-channel MOSFET. external turned only when load voltage less than 100mV. Ground Startup Timer Input. Leave floating connect timing capacitor from CTON GND. Startup Retry Timers section. Slow Comparator Speed Setting. Leave floating connect timing capacitor from CSPD GND. Slow Comparator Response Time section.
AUXVCC
SENSE GATE CEXT
LLMON CTON CSPD
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection MAX4271/MAX4272/MAX4273
Description (continued)
MAX4271 MAX4272 MAX4273 NAME FUNCTION Startup Retry Timers Input. Controls startup time autoretry time (32x startup time) MAX4272, only autoretry time MAX4273, only startup time MAX4271. Leave floating connect timing capacitor from CTIM GND. Connect latched mode (this prevents autoretry MAX4273). Startup Retry Timers section. Status Output. High indicates startup completed with fault (Table STAT open-drain output. Comparator Input. Connect high normal operation; connect force MOSFET off. Comparator threshold VTH,ON 0.6V allows precise control over shutdown feature. Pulse 20µs unlatch after fault (MAX4273 latched mode, MAX4271). Negative pulses ignored during autoretry (MAX4273 autoretry mode, MAX4272). Reset Comparators section. 1.2V Reference Output. bypass with capacitor GND. Uncommitted Comparator Input. Controls OUTC. Uncommitted Comparator Output. OUTC goes high 150ms after goes high. OUTC goes immediately after goes low. OUTC open-drain output.
CTIM
STAT
OUTC
Detailed Description
MAX4271/MAX4272/MAX4273 circuit breaker designed hot-swap applications where line card inserted into live backplane. Normally, when line card plugged into live backplane, card's discharged filter capacitors provide impedance that momentarily cause main power supply collapse. MAX4271/MAX4272/MAX4273 designed reside either backplane removable card provide inrush current limiting short-circuit protection. This achieved using external N-channel MOSFET, external current-sense resistor, on-chip comparators. Figures show functional diagrams. timing voltage levels several critical parameters adjusted with external resistors, external capacitors, strapping. timing components optional; without them, part nominal values, shown Electrical Characteristics. parameters that adjusted are: Current-limit threshold Slow comparator response time Startup timer Fast comparator threshold
Autoretry timeout period (time part shut down after overcurrent event) Fault management (latched/autoretry) Current overload threshold
Startup Mode
CTIM (MAX4271/MAX4272) CTON (MAX4273) sets startup period (see Startup Retry Timers). startup period begins after three conditions met: 150ms after exceeds UVLO threshold (see Over/Undervoltage Lockouts) 10µs after >0.6V device longer retry mode. During startup, slow comparator disabled inrush current limited ways: Slow ramping current load controlling external MOSFET gate voltage Limiting current load regulating voltage across external current-sense resistor
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection MAX4271/MAX4272/MAX4273
CSPD CSPD 2.45V
MAX4271 MAX4272
SLOW COMPARATOR
VSC,TH 50mV RSENSE
INPUT UVLO 150ms DELAY RISING STAT CTIM CTIM
VSC,TH 200mV FAST COMPARATOR
SENSE GATE DRIVE DISCHARGE ENABLE LOGIC CONTROL 0.1V CHARGE PUMP (1MHz) GATE OVLO COMPARATOR 0.6V VOUT GATE
Figure MAX4271/MAX4272 Functional Diagram
Unlike other circuit breaker ICs, MAX4271/ MAX4272/MAX4273 regulate current preset level instead completely turning external N-FET overcurrent condition occurs during startup. startup mode, gate drive current limited 100µA decreases with increase gate voltage (see Gate Charge Current Gate Voltage Typical Operating Characteristics). This allows controller slowly enhance MOSFET. fast comparator detects overcurrent, gate voltage momentarily discharged with fixed 70µA current until load current through sense resistor (RSENSE) decreases below threshold point. This effectively regulates inrush current during startup. Figure shows startup waveforms. STAT goes high startup period fault condition present.
Normal Operation (DualSpeed/BiLevel)
normal operation (after startup timer expired), protection provided turning external MOSFET when fault condition encountered. DualSpeed/BiLevel fault protection incorporates comparators with different thresholds response times monitor current: Slow comparator. This comparator externally response time (from 20µs seconds) fixed 50mV threshold voltage. slow comparator ignores low-amplitude momentary current glitches. After extended overcurrent condition, fault generated MOSFET gate slowly discharged. Fast comparator. This comparator fixed 350ns response time 200mV threshold voltage (adjustable from 50mV 750mV MAX4273). fast comparator turns MOSFET immediately after detects large amplitude event such short circuit.
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection MAX4271/MAX4272/MAX4273
CSPD AUXVCC 2.45V VFC,TH 50mV
MAX4273
1.2V INPUT UVLO 150ms DELAY RISING SLOW COMPARATOR VFC,TH 200mV RSENSE
FAST COMPARATOR VFC,TH 50mV 750mV 10µA SENSE CEXT CEXT AUXVCC DISCHARGE ENABLE GATE DRIVE CHARGE PUMP 1MHz 0.1V GATE OVLO GATE
AUXVCC
STAT
CTIM CTIM CTON CTON
LOGIC CONTROL
0.1V
OUTPUT OVLO
LLMON
COMPARATOR 0.6V RESET COMPARATOR 150ms DELAY RISING
OUTC
0.6V VOUT
Figure MAX4273 Functional Diagram
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection
each case, when fault encountered, status (STAT) goes low, MAX4273, device discharges output voltage through resistor from LLMON GND. After fault, MAX4271 stays latched MAX4272 enters retry mode, while MAX4273 selectable latched retry mode. Figure shows waveforms fault condition. trip point 1.2V. Therefore, pulsing current with duty cycle greater (i.e., current above threshold level time) considered fault condition even never higher than threshold longer than slow comparator's response time. discharge rate depends N-FET gate capacitance external capacitance GATE. MAX4273, CEXT remains connected capacitance this point discharged same current. This increases discharge time. Once fault condition detected, STAT goes device goes into retry latched mode. Fast Comparator fast comparator behaves differently according operating mode. During startup, fast comparator part simple current regulator. When sensed current above fast comparator threshold, gate discharged with 70µA current source. When sensed current drops below threshold, charge pump turns again. sensed current will rise fall near threshold fast comparator charge-pump propagation delay. gate voltage will roughly sawtooth shaped, load current will present ripple. ripple reduced adding capacitor from GATE GND.
MAX4271/MAX4272/MAX4273
BiLevel Fault Protection
Slow Comparator slow comparator disabled startup while external MOSFET turning This allows part ignore higher-than-normal inrush current charging board capacitors when card first plugged slow comparator detects overload condition while normal operation (after startup completed), turns external MOSFET discharging gate capacitance with 200µA current. slow comparator threshold 50mV default delay 20µs (CSPD floating), allowing ignore power-supply glitches noise. response time lengthened with external capacitor CSPD (Figure 10). overcurrent condition continuous, then duration above threshold minus duration below must greater than 20µs external programmed value) device trip. When current above threshold, CSPD charged with current source. fault detected when CSPD charged
STAT STAT tSTART VGATE 2.7V VOUT VGATE VOUT IFAST, VGATE 2.7V VOUT
CBOARD LARGE CBOARD ILIM ILOAD tOFF
ILOAD
Figure Startup Waveforms
Figure Response Fault Condition
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection MAX4271/MAX4272/MAX4273
sensed current still high after startup timer expires, MOSFET gate discharged completely described below. normal operation (after startup), fast comparator used emergency switch. load current reaches fast comparator threshold, device quickly forces MOSFET completely. This could happen event serious current overload dead short. fast comparator 350ns response time discharges GATE with current. Given 1000pF gate capacitance gate voltage, MOSFET will about 12µs. additional capacitance connected between GATE slow down startup time also increases turn-off time. MAX4273, CEXT goes high impedance during fast discharge. This reduces effective capacitance GATE capacitor used between GATE CEXT, allows MOSFET quickly turn off. turn, this allows adjustment MOSFET charging time without affecting fast discharge rate, although does affect slow discharge rate. MAX4271/MAX4272 fast comparator threshold four times slow comparator threshold (i.e., 200mV). MAX4273 fast comparator threshold 200mV connecting GND, disabled connecting adjustable external resistor connected (see Fast Comparator Threshold (RTH)). Pulse 20µs (min) restart after fault (MAX4271/MAX4273 latched mode). Negative pulses ignored during autoretry (MAX4273 autoretry mode, MAX4272). capacitor CTIM affects MAX4272's retry timeout period (time part shut down after overcurrent event) startup time (see Electrical Characteristics). retry timeout period fixed times startup time order minimize power dissipation external MOSFET case short-circuit condition (see MOSFET Thermal Considerations). This issue parts latched during fault condition since they stay until commanded MAX4273 configured retry mode separate startup timer capacitor (CTON) retry timeout capacitor (CTIM). This allows user change ratio between startup time retry timeout period.
Status Output
status output open-drain output that goes under following conditions: During UVLO delay period startup Forced <0.6V) overcurrent condition retry timeout period latched off, latched parts) STAT high only part normal mode faults present (Table Figure shows status (STAT) output timing diagram.
Latched/Autoretry
MAX4271 MOSFET driver stays latched after fault condition until reset negative-going pulse pin. MAX4272 periodically turned after fault condition with timeout duration external timing capacitor CTIM. MAX4273 selectable latched mode retry mode. Connect CTIM device latched mode, external capacitor CTIM retry timeout.
Over/Undervoltage Lockouts
UVLO prevents MAX4271/MAX4272/MAX4273 from turning external MOSFET until exceeds lockout threshold (2.25V min) 150ms. UVLO protects external MOSFET from insufficient gate drive voltage. 150ms timeout ensures that board fully plugged into backplane that
Table Status Output Truth Table
UVLO DELAY PERIOD PART STARTUP High OVERCURRENT CONDITION PART RETRY-TIMEOUT PERIOD LATCHED OVERCURRENT CONDITION) STAT (STATUS) High
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection
stable. input voltage transient below UVLO threshold will reset device initiate startup sequence. These devices also have overvoltage lockout (OVLO) feature that prevents device from restarting after fault condition discharge been completed. VGATE discharged below 0.1V. Additionally, MAX4273 LLMON discharges load line with pulldown prevents startup until load voltage below 0.1V. Since MAX4271/MAX4272 monitor output voltage, startup sequence initiated while board capacitance still charged. large board capacitance short startup period prevent MAX4272 from charging completely startup period. MAX4272 responds these conditions charging capacitor with bursts defined duty cycle period tRETRY. charging will complete after several retries unless resistive load current load excessively discharges board capacitance during retry timeout. This feature applies MAX4273 LLMON left floating connected GND. prevent multiple charging bursts, ensure that timer exceeds minimum time required complete charge board capacitance (see Component Selection).
Applications Information
Component Selection
N-Channel MOSFET Select external N-channel MOSFET according application's current level. Table lists some recommended components. MOSFET's on-resistance (RDS(ON)) should chosen enough have minimum voltage drop full load limit MOSFET power dissipation. High RDS(ON) cause output ripple board pulsing loads triggers external undervoltage reset monitor full load. Determine device power-rating requirement accommodate short circuit board startup with device
MAX4271/MAX4272/MAX4273
RSENSE MAX4271 MAX4272 SENSE
GATE DRIVE CHARGE PUMP GATE VOUT CBOARD
Gate Overvoltage Protection
New-generation MOSFETs have absolute maximum rating gate-to-source voltage (VGS). protect these MOSFETs, MAX4271/MAX4272 limit gate-to-drain voltage (the MAX4273 limits gate-tosource voltage) +7.5V with internal zener diode. protection provided negative (MAX4271/ MAX4272). GATE discharged ground faster than output voltage, external small-signal protection diode (D1) used, shown Figure MAX4273 protection diode internal.
tSTART 1.2V CTIM (CTON)* FAULT CONDITION, FALLING EDGE STAT FAULT CONDITIONS PRESENT *MAX4273 ONLY
Figure External Gate-Source Protection
Table Recommended N-Channel MOSFETs
PART NUMBER IRF7413 IRF7401 IRL3502S MMSF3300 MMSF5N02H MTB60N05H FDS6670A NDS8426A FDB8030L Fairchild Motorola International Rectifier MANUFACTURER DESCRIPTION 11m, 22m, D2PAK, 20m, 30m, 14m, D2PAK, 10m, 13.5m, 4.5m, D2PAK,
Figure Status (STAT) Output Timing Diagram
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection MAX4271/MAX4272/MAX4273
configured automatic retry mode (see MOSFET Thermal Considerations). Using MAX4271/MAX4273 latched mode allows consideration MOSFETs with higher RDS(ON) lower power ratings. MOSFET typically withstand single-shot pulses with higher dissipation than specified package rating. MOSFET gate capacitance necessary since inrush current limiting achieved limiting gate dv/dt. Table lists some recommended manufacturers components. Sense Resistor slow comparator threshold voltage 50mV. Select sense resistor that causes 50mV voltage drop current level above maximum normal operating current; typically, overload current times nominal load current. fast comparator threshold typically 200mV. This will fault current limit four times overload current limit. MAX4273 fast comparator threshold between 50mV 750mV; Table detailed listing. Choose sense resistor power rating according device configuration. retry mode selected, PRSENSE (IOVERLOAD)2 RSENSE; retry selected, then PRSENSE (IFAULT)2 RSENSE (tON/tRETRY). Fast Comparator Threshold (RTH) (MAX4273) fast comparator threshold determined external resistor connected RTH. select threshold voltages between 50mV 750mV, resistor values between according Figure Resistor values between recommended. Setting threshold voltage fast comparator below 50mV will effectively override slow comparator operation. MAX4273 fast comparator disabled shorting (VIN 25mV less). Ground threshold 200mV internally. Startup Retry Timers (CTIM, CTON) startup (tSTART) retry (tRETRY) timers determined capacitors connected CTIM CTON. capacitor connected CTIM functions three devices follows:
DEVICE MAX4271 MAX4272 MAX4273 CTIM FUNCTION Startup time Startup time sets retry timer Sets retry timer
Table Component Manufacturers
COMPONENT Sense Resistors Fairchild MOSFETS International Rectifier Motorola MANUFACTURER Dale-Vishay PHONE 402-564-3131 704-264-8861 888-522-5372 310-322-3331 602-244-3576 www.vishay.com www.irctt.com www.fairchildsemi.com www.irf.com www.mot-sps.com/ppd/
Table Current Levels RSENSE
RSENSE PART NUMBER MAX4271/MAX4272 MAX4273 MAX4271/MAX4272 MAX4273 MAX4271/MAX4272 MAX4273 OVERLOAD THRESHOLD SLOW COMPARATOR FAULT CURRENT THRESHOLD FAST COMPARATOR
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection
CTON determines maximum time allowed complete turn-on MAX4273. default values turn-on time (tON) tRETRY chosen leaving these pins floating; they 10µs 320µs, respectively. These also minimum values (not controlled dependent stray capacitance). Longer timings determined size capacitor according Figure determined Table which lists startup retry timing parameters. timer long enough allow MOSFET enhanced load capacitor charged completely There ways completing startup sequence. Case describes startup sequence that does current-limiting feature slowly turns MOSFET limiting gate dv/dt. Case uses currentlimiting feature turns MOSFET fast possible while still preventing high inrush current. Case Startup Without Current Regulation There three ways turn MOSFET without reaching fast comparator current limit: board capacitance small, inrush current low. gate capacitance high, MOSFET turns slowly. fast comparator disabled (MAX4273 only). three cases, determined only charge required enhance MOSFET. Effectively, small gate-charging current limits output voltage dv/dt. This time extended connecting external capacitor between GATE (MAX4271/ MAX4272) (Figure between GATE CEXT (MAX4273). turn-on time dominated external gate capacitance this value considerably higher than MOSFET gate capacitance. Table shows timing required enhance recommended MOSFET with without external capacitor; Figure shows related waveforms timing diagrams. (See Time Charge Gate GATE Startup Time with CBOARD Typical Operating Characteristics.) Remember that high gate capacitance also increases turn-off time except case MAX4273 fast fault. external gate capacitor used, necessary. prevents MOSFET self-oscillations that occur when CGATE high while CBOARD low. Electrical characteristics specified manufacturer's data sheet are: FDS6670A: CISS 3200pF, QT(MAX) 50nC, RDS(ON) 8.2m
MAX4271/MAX4272/MAX4273
FAST COMPARATOR THRESHOLD VOLTAGE
VTH, (mV) DISABLED INDETERMINATE, RECOMMENDED VTH,FC (mV)/10
IRF7401: CISS 1600pF, QT(MAX) 48nC, RDS(ON) MMSF5N03HD: 1200pF, (MAX) 21nC, RDS(ON)
Figure Fast Comparator Threshold
Table Startup Retry Timing Parameters
PART MAX4271 MAX4272 MAX4273* DEFAULT (µs) EXTERNALLY (ms) 0.31 CTIM (nF) (ms) 0.31 CTIM (nF) (ms) 0.31 CTON (nF) DEFAULT (µs) tRETRY EXTERNALLY retry available tRETRY (ms) CTIM (nF) tRETRY (ms) CTIM (nF)
*MAX4273 retry feature disabled connecting CTIM VIN.
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection MAX4271/MAX4272/MAX4273
Table "No-Overcurrent" Turn-On Timing (Startup Without Current Limit)
DEVICE Fairchild FDS6670A International Rectifier IRF7401 Motorola MMSF5N03HD CGATE (nF) MOSFET (ms) 0.22 0.175 0.101 0.16 0.130 0.074 0.19 0.16 0.073 0.07 0.54 0.075 0.54 0.033 0.470 MOSFET tOFF (ms) 0.13 0.13 0.067 0.145 1.95 0.16 0.085 1.95
RSENSE
tRETRY CTON CTIM
10,000 tRETRY CTIM (MAX4272/MAX4273) 1000 tRETRY (ms) 0.01 0.01
VOUT
CBOARD RPULLUP STAT SENSE GATE CGATE
MAX4271 MAX4272 MAX4273 CTIM CTIM
CSPD CTIM (MAX4271/MAX4272) CTON (MAX4273) 1000 CSPD
CAPACITANCE (nF) *OPTIONAL (SEE TEXT)
Figure Startup Retry Timeout
Figure Operation with External Capacitor
Case Startup With Current Regulation applications where board capacitance (CBOARD) VOUT high, inrush current causes voltage drop across RSENSE that exceeds fast comparator threshold (VFC,TH). this case, current charging CBOARD considered constant turn-on time determined CBOARD IFAST,SET where maximum load current IFAST,SET VFC,TH RSENSE. Figure shows waveforms timing diagrams startup transient with current regulation. (See Startup Time (CBOARD 470µF) Typical Operating Characteristics.) When operating under this condition, external gate capacitor required. Adding external gate capacitor GATE reduces regulat-
current ripple increases tOFF increasing gate delay (td) (Figure actual startup time determined longer timings Case Case startup timer tSTART guarantee enough time output voltage settle; also take into consideration device parameter variation. Retry retry timer defines dead time before tries restart startup sequence following fault detection. This feature available MAX4272/MAX4273. Before selecting retry timer value, determine long temporary high-current fault condition present. event permanent fault, automatic retry will effectively force current pulses through
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection
MOSFET with duty cycle equal tON/tRETRY with current equal IFAST,SET. Therefore, particular care taken when choosing between immediate retry board space needed manage power dissipation capabilities MOSFET (see Thermal Considerations). duty cycle fixed 1/32 MAX4272, varied MAX4273 choosing CTIM CTON independently. Additional External Gate Capacitance (CEXT) external gate capacitance connected GATE. This increases time required enhance MOSFET further limits output rise time. MAX4271/MAX4272, connect external capacitor between GATE GND. MAX4273, external capacitor connected between GATE CEXT GND. capacitor connected CEXT, discharged ground during slow comparator fault left floating during fast comparator fault; this allows device turn external MOSFET faster during critical faults. (CEXT biased VIN; therefore, nonpolarized capacitor). Capacitance connected from GATE CEXT does little decrease regulated current ripple. small capacitor (5nF) from GATE GND. charging discharging time CGATE graphs Typical Operating Characteristics. Slow Comparator Response Time (CSPD) slow comparator threshold 50mV, response time determined external capacitor connected CSPD (Figure 10). minimum response time 20µs (typ) achieved leaving this floating. This time determined internally affected stray capacitance CSPD 100pF).
SLOW COMPARATOR RESPONSE TIME CSPD
1000
slow comparator response time longer than normal operation load transients (see Slow Comparator).
MAX4271/MAX4272/MAX4273
Reset Comparators
comparator controls ON/OFF function these devices. comparator precision voltage comparator that used temperature monitoring additional UVLO (Figure 11). MAX4273 also features uncommitted delayed comparator. This comparator used voltage monitoring, power sequencing, generating power-on reset signal on-card microprocessors (Figure 12). Both comparator threshold voltages VREF/2 0.6V with (typ) hysteresis. uncommitted comparator OUTC output opendrain output, asserted when input voltage (INC) below threshold voltage. goes into high-impedance state 150ms after voltage risen above threshold. delay negative-going edges 10µs. Figure shows MAX4273 used monitor precisely temperature external device such MOSFET. This configuration uses uncommitted comparator UVLO higher level running output into comparator's input. comparator initiates startup when input voltage (VON) rises above threshold voltage turns MOSFET when voltage falls below threshold. propagation delay 10µs going high low. comparator also used reset MAX4271/MAX4273 (when CTIM VIN) after fault condition (see Latched/Autoretry).
VREF MAX4271 MAX4272 MAX4273 LOGIC CONTROL 0.6V
RESPONSE TIME (ms) tCSPD (ms) CSPD (nF)
0.01 0.01
1000
CSPD (nF)
(VREF VALUE RESISTOR LIMIT TEMPERATURE VREF REFERENCE VOLTAGE AVAILABLE
Figure Slow Comparator Response Time CSPD
Figure Temperature Monitoring Protection
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection MAX4271/MAX4272/MAX4273
BACKPLANE
SENSE GATE LLMON
REMOVABLE CARD
SENSE GATE MAX4271 MAX4272 MAX4273
MAX4273
OUTC RESET
Figure Power-On Reset
VOUT RESET SENSE GATE
Figure Fail-Safe Connector
MAX4273
OUTC
LLMON
gate drive until MOSFET turned main supply recovers. capacitor charged from through internal switch during normal operation.
Maximum Load Capacitance
Figure Power-On Reset Temperature
comparator inputs STAT OUTC pulled voltages independently VIN, thus allowing parts daisy-chained turned through internal protection diodes. some applications, useful connectors with staggered leads. Figure forces removable board powered only when connections made.
Auxiliary auxiliary available MAX4273 used sustain input voltage required device operate during short-circuit condition board. When short occurs, main system power supply could collapse MAX4273 will have enough voltage keep gate drive operational turn external MOSFET. fault removed, system could remain sustained short-circuit state. Connect capacitor from AUXVCC GND. This capacitor will deliver necessary energy
MAX4271/MAX4272/MAX4273 used backplane regulate current upon insertion removable card (Figure 16). This allows multiple cards with different input capacitance inserted into same slot even card doesn't have on-board hotswap protection. MAX4271/MAX4272/MAX4273 current-limiting feature active during startup period CTIM. startup period triggered connected through trace card. Once tSTART expired (timed out), load capacitance charged fault condition detected. ensure startup with fixed CTIM, tSTART longer than time required charge board capacitance. maximum load capacitance calculated follows: CBOARD tSTART IFAST,SET
Input Transients
voltage must above UVLO during inrush fault conditions. When short condition occurs board, fault current higher than fast comparator current limit. gate voltage
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection MAX4271/MAX4272/MAX4273
100k
SENSE
GATE LLMON
MAX4273
OUTC RESET
Figure Adjustable Undervoltage Lockout Output Voltage Reset Generator
discharged immediately, note that MOSFET completely until VTH. main system power supply collapses below UVLO, MAX4271/ MAX4272/MAX4273 will force device restart startup mode with 150ms delay once supply recovered. main system power supply must able deliver this fault current without excessive voltage drop. MOSFET turned very short time; therefore, resulting dv/dt considerable. backplane delivering power external card must have fairly inductance limit voltage transients caused removal fault. Bypassing input with small capacitor alleviates false UVLO trips these transients.
BACKPLANE
REMOVABLE CARD WITH HOT-INSERTION PROTECTION
VOUT
CBOARD
SENSE MAX4271 MAX4272 MAX4273
GATE
CTIM
MOSFET Thermal Considerations
During normal operation, MOSFET dissipates little power, fully turned RDS(ON) minimal. power dissipated normal operation ILOAD2 RDS(ON). considerable amount power dissipated during startup turn-off transients. design must take into consideration worst-case scenario continuous short-circuit fault present board. cases need considered: single turn-on with device latched after fault (when using MAX4271 MAX4273 latched mode) continuous automatic retry (when using MAX4272 MAX4273 retry mode) following equation calculate maximum transient thermal resistance °C/W) required output short ground: (max) (TJMAX (VIN IFAST, SET)
Figure Using MAX4271/MAX4272/MAX4273 Backplane
MOSFET manufacturers typically include curves transient thermal resistance, package (Figure 17). Find thermal impedance MOSFET using START pulse duration choosing single pulse curve latched mode parts choosing duty cycle 0.03 curve MAX4272 (the duty cycle fixed 32:1). required less than that package, reduce tSTART, reduce IFAST,SET, heatsink MOSFET, choose with better thermal characteristics.
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection MAX4271/MAX4272/MAX4273
0.50
THERMAL RESPONSE (ZJA)
0.20 0.10 0.05 SINGLE PULSE (THERMAL RESPONSE) NOTES: DUTY FACTOR PEAK
0.02 0.01
0.0001 0.001 0.01 RECTANGULAR PULSE DURATION
Figure Example Curves (from IRF7413A) Maximum Effective Transient Thermal Impedance, Junction Ambient
MAX4273 retry mode, duty cycle adjusted. MOSFET curve tSTART pulse duration choose maximum duty cycle, Calculate retry time: tRETRY tSTART Figure determine CTIM given tRETRY.
MOSFET pulsed drain current limit 58A. Another consideration setting current limit system requirement. Systems glitch load transients present. this example, load transient will limited 10A: System current limit Current-sense resistor Fast comparator threshold 100mV Select from Figure Startup timer. Startup current System current limit CBOARD 1000µF 1000µF 500µs Give factor guardband startup timer. tSTART 1.0ms From Figure CTON 3000pF. Select Retry Timeout. IMAX 10A. Peak junction temperature, 150°CJ Peak ambient temperature, 85°CA
Design Procedure (MAX4273)
GIVEN: Hot-swap supply 1000µF card MOSFET IRF7413A: RDS(on) 0.0135 Operating current Overload current System current limit Retry enabled PROCEDURE: Select current sense resistor: Slow comparator threshold 50mV Overload current Current-sense resistor value 50mV/5A device will initiate slow fault load current greater than longer than 20µs after startup. fast comparator threshold (RTH).
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection MAX4271/MAX4272/MAX4273
Calculate MOSFET thermal resistance required short ground. (150°C 85°C) 10A) 1.30°C/W Using START pulse duration, Figure select duty cycle. duty cycle should about 0.01 less. This implies tRETRY tSTART 0.01 100ms. From Figure CTIM 10nF.
Layout Considerations
take full tracking advantage switch response time output fault condition, important keep traces short possible maximize high-current trace dimensions reduce effect undesirable parasitic inductance. Place MAX4271/MAX4272/MAX4273 close card's connector. ground plane minimize impedance inductance. Minimize currentsense resistor trace length (<10mm), ensure accurate current sensing with Kelvin connections (Figure 18). When output short circuited, voltage drop across external MOSFET becomes large. Hence, power dissipation across switch increases, does temperature. efficient achieve good power dissipation surface-mount package copper pads directly under MOSFET package both sides board. Connect pads ground plane through vias, enlarged copper mounting pads side board.
HIGH-CURRENT PATH
SENSE RESISTOR
MAX4271 MAX4272 MAX4273
Figure Kelvin Connections Current-Sense Resistors
Configurations
VIEW
AUXVCC SENSE GATE STAT CTIM CSPD SENSE OUTC
MAX4273
STAT CTIM CSPD CTON
MAX4271 MAX4272
GATE CEXT LLMON
QSOP/SO
Current-Limiting Swap Controllers with Autoretry, DualSpeed/BiLevel Fault Protection MAX4271/MAX4272/MAX4273
Package Information
SOICN.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 2001 Maxim Integrated Products Printed registered trademark Maxim Integrated Products.
QSOP.EPS
Other recent searches
ST6129T - ST6129T ST6129T Datasheet
SdL-3 - SdL-3 SdL-3 Datasheet
PB100 - PB100 PB100 Datasheet
P300A - P300A P300A Datasheet
P300M - P300M P300M Datasheet
NJU7757 - NJU7757 NJU7757 Datasheet
NJU7757 - NJU7757 NJU7757 Datasheet
58C-MOS - 58C-MOS 58C-MOS Datasheet
NJU7758 - NJU7758 NJU7758 Datasheet
NJU7757 - NJU7757 NJU7757 Datasheet
58F4 - 58F4 58F4 Datasheet
MEA2010PE - MEA2010PE MEA2010PE Datasheet
IDT72V73260 - IDT72V73260 IDT72V73260 Datasheet
Privacy Policy | Disclaimer
© 2012 Datasheet Archive
