Low-Voltage, Dual Hot-Swap Controllers with Independent ON/OFF Control
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19-2496; 12/04
Low-Voltage, Dual Hot-Swap Controllers with Independent ON/OFF Control
MAX5918 MAX5919 +13.2V dual hot-swap controllers with independent on/off control complete protection dual-supply systems. They allow safe insertion removal circuit cards into live backplanes. MAX5918 MAX5919 operate down provided inputs above 2.7V 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. MAX5918 MAX5919 hot-swap controllers prevent such problems gradually ramping output voltage regulating current preset limit when board plugged allowing system stabilize safely. After startup cycle completed, on-chip comparators provide VariableSpeed/BiLevelprotection against short-circuit overcurrent faults, well immunity against system noise load transients. event fault condition, load disconnected. MAX5918L MAX5919L must unlatched after fault MAX5918A MAX5919A automatically restart after fault. MAX5918 MAX5919 integrate on-board charge pump drive gates low-cost, external Nchannel MOSFETs. devices offer integrated features like startup current regulation current glitch protection eliminate external timing resistors capacitors. These devices provide open-drain status outputs, adjustable startup timer adjustable current limits. MAX5918 provides output undervoltage/overvoltage protection each channel, while MAX5919 provides undervoltage/overvoltage monitoring each channel. MAX5918 MAX5919 available spacesaving 16-pin QSOP package specified over extended -40°C +85°C temperature range.
ATION EVALU AVAILA
Features
Safe Swap +13.2V Power Supplies with VIN1 VIN2 2.7V Independent On/Off Control Each Channel Internal Charge Pumps Generate N-Channel MOSFET Gate Drives Inrush Current Regulated Startup Circuit Breaker Function Adjustable Circuit Breaker/Current-Limit Threshold from 25mV 100mV VariableSpeed/BiLevel Circuit Breaker Response Autoretry Latched Fault Management Status Outputs Indicate Fault/Safe Condition Output Undervoltage Overvoltage Monitoring Protection
MAX5918/MAX5919
Ordering Information
PART MAX5918AEEE MAX5918LEEE MAX5919AEEE MAX5919LEEE TEMP RANGE -40°C +85°C -40°C +85°C -40°C +85°C -40°C +85°C PIN-PACKAGE QSOP QSOP QSOP QSOP
Selector Guide Typical Application Circuit appear data sheet.
Configuration
VIEW
PGOOD1 SENSE1 GATE1 LIM1 MON1 PGOOD2
Applications
Base Station Line Cards Network Switches, Routers, Hubs Solid-State Circuit Breakers RAID Power-Supply Sequencing Plug-In Daughter Cards Portable Computer Device Bays (Docking Stations)
MAX5918 MAX5919
SENSE2 GATE2 LIM2 MON2
Variable Speed/BiLevel trademark Maxim Integrated Products, Inc.
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.
Low-Voltage, Dual Hot-Swap Controllers with Independent ON/OFF Control MAX5918/MAX5919
ABSOLUTE MAXIMUM RATINGS
GND.+14V GATE_ .-0.3V (VIN_ 6.2V) ON_, PGOOD_, GND.-0.3V higher (VIN1 0.3V) (VIN2 0.3V) SENSE_, MON_, LIM_ .-0.3V (VIN_ 0.3V) Current into .±50mA Continuous Power Dissipation +70°C) 16-Pin QSOP (derate 8.3mW/°C above +70°C).667mW Operating Temperature Range .-40°C +85°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_ +13.2V provided least supply higher than +2.7V, VON1 VON2 +2.7V, -40°C +85°C, unless otherwise noted. Typical values VIN1 +5V, VIN2 +3.3V, +25°C.) (Note
PARAMETER POWER SUPPLIES Input Voltage Range Supply Current CURRENT CONTROL Slow-Comparator Threshold (VIN_ VSENSE_) (Note Slow-Comparator Response Time (Note Fast-Comparator Threshold (VIN_ VSENSE_) Fast-Comparator Response Time (VIN_ VSENSE_) SENSE Input Bias Current MOSFET DRIVER RTIM 100k (maximum value) Startup Period (Note tSTART +85°C -40°C +85°C 0.35 10.8 10.8 0.45 0.85 0.875 0.90 13.6 0.55 VSC,TH RLIM 300k tSCD VSU,TH VFC,TH tFCD SENSE overdrive 10mV overdrive During startup VIN_ VSENSE_; normal operation 10mV overdrive, from overload condition VSENSE_ VIN_ +25°C -40°C +85°C 22.5 20.5 VSC,TH VSC,TH 0.03 27.5 27.5 Other +2.7V IIN1 IIN2, VIN1 +5V, VIN2 +3.3V 13.2 SYMBOL CONDITIONS UNITS
RTIM (minimum value) floating Charging, VGATE_ +5V, VIN_ +10V (Note
Average Gate Current
IGATE
Discharging, triggered fault when 0.875V VGATE_ VIN_, IGATE_ high Hysteresis 10mV overdrive VIN_ 13.2V VIN_ 2.7V 3.0V
Gate-Drive Voltage COMPARATOR Threshold Propagation Delay
VDRIVE
VON_,TH
Low-Voltage, Dual Hot-Swap Controllers with Independent ON/OFF Control
ELECTRICAL CHARACTERISTICS (continued)
(VIN_ +13.2V provided least supply higher than +2.7V, VON1 VON2 +2.7V, -40°C +85°C, unless otherwise noted. Typical values VIN1 +5V, VIN2 +3.3V, +25°C.) (Note
PARAMETER Input Bias Current Pulse Width DIGITAL OUTPUT (PGOOD_) Output Leakage Current Output Voltage PGOOD_ Delay tPGDLY VPGOOD_ 13.2V ISINK After tSTART, MON_ VIN_ Overvoltage Undervoltage VMON_ 600mV Startup initiated when this threshold reached VIN1 VIN2, VON_ 0.875V Hysteresis UVLO Glitch Filter Reset Time UVLO Startup Delay SHUTDOWN LATCH/RESTART Autoretry Delay tRETRY Delay time restart after fault shutdown tSTART tD,UVLO VIN_ toggled below UVLO unlatch after fault VIN_ step from 2.8V 37.5 0.75 0.03 SYMBOL IBON tUNLATCH CONDITIONS VON_ 4.5V VIN1 VIN2 +13.2V VON_ 4.5V VON_ 4.5V unlatch after latched fault 0.03 0.03 UNITS
MAX5918/MAX5919
OUTPUT VOLTAGE MONITORS (MON1, MON2) MON_ Trip Threshold MON_ Glitch Filter MON_ Input Bias Current UNDERVOLTAGE LOCKOUT (UVLO) UVLO Threshold VUVLO 2.10 2.67 VMON
Note devices 100% tested +25°C +85°C. Limits -40°C guaranteed design. Note MAX5918/MAX5919 slow-comparator threshold adjustable. VSC,TH RLIM 0.25µA 25mV (see Typical Operating Characteristics). Note current-limit slow-comparator response time weighted against amount overcurrent, higher overcurrent condition, faster response time (see Typical Operating Characteristics). Note startup period (tSTART) time during which slow comparator ignored device acts current-limiter regulating sense current with fast comparator (see Startup Period section). Note current available GATE function VGATE (see Typical Operating Characteristics).
Low-Voltage, Dual Hot-Swap Controllers with Independent ON/OFF Control MAX5918/MAX5919
Typical Operating Characteristics
(Typical Operating Circuits, Fairchild FDB7090L, VIN1 +5V, VIN2 +3.3V, VON1 VON2 +2.7V, +25°C, unless otherwise noted. Channels identical performance. Where characteristics interchangeable, channels referred
SUPPLY CURRENT SUPPLY VOLTAGE
MAX5918/19 toc01
TOTAL SUPPLY CURRENT SUPPLY VOLTAGE
MAX5918/19 toc02
SUPPLY CURRENT TEMPERATURE
VON1 VIN1 VON2 VIN2
MAX5918/19 toc03
(mA)
VINY VON1 VON2 2.7V
(mA)
IIN1 IIN2
IINX IINY
(mA)
IIN1
IINX
IINY
VINY 5.0V VON1 VON2 3.3V VON1 VON2 1.5V VON1 VON2
IIN2
VINX
VINX
TEMPERATURE (°C)
GATE-DRIVE VOLTAGE INPUT VOLTAGE
MAX5918/19 toc04
GATE CHARGE CURRENT GATE VOLTAGE
MAX5918/19 toc05
GATE CHARGE CURRENT TEMPERATURE
GATE CHARGE CURRENT (µA) VINY 2.7V VGATEX VINX VINX 13.2V VINX
MAX5918/19 toc06 MAX5918/19 toc09
GATE-DRIVE VOLTAGE VINY 2.7V
GATE CHARGE CURRENT (µA) VINX 13.2V VINX VINX VINY 2.7V
VGATEX
VINX
TEMPERATURE (°C)
GATE STRONG DISCHARGE CURRENT GATE VOLTAGE
MAX5918/19 toc07
GATE STRONG DISCHARGE CURRENT TEMPERATURE
MAX5918/19 toc08
TURN-OFF TIME SENSE VOLTAGE
SLOW-COMP. THRESHOLD TURN-OFF TIME (ms) FAST-COMP. THRESHOLD
GATE DISCHARGE CURRENT (mA) VGATEX VINX VINY 2.7V VGATEX VINX 6.2V VINX VINX 13.2V
GATE DISCHARGE CURRENT (mA) VINX VINX 13.2V
VON1 VON2
VON1 VON2 VINY 2.7V VGATEX VINX 6.2V
0.01
0.001 VINX 0.0001 TEMPERATURE (°C) VSENSE (mV)
Low-Voltage, Dual Hot-Swap Controllers with Independent ON/OFF Control MAX5918/MAX5919
Typical Operating Characteristics (continued)
(Typical Operating Circuits, Fairchild FDB7090L, VIN1 +5V, VIN2 +3.3V, VON1 VON2 +2.7V, +25°C, unless otherwise noted. Channels identical performance. Where characteristics interchangeable, channels referred
TURN-OFF TIME SENSE VOLTAGE (EXPANDED SCALE)
MAX5918/19 toc10
SLOW-COMPARATOR THRESHOLD RLIM
MAX5918/19 toc11
STARTUP PERIOD RTIM
MAX5918/19 toc12
tSTART (ms)
TURN-OFF TIME (ms)
SLOW-COMP. THRESHOLD
VSC,TH (mV)
VSENSE (mV)
RLIM
RTIM
TURN-OFF TIME SLOW-COMPARATOR FAULT
MAX5918/19 toc13
TURN-OFF TIME FAST-COMPARATOR FAULT
MAX5918/19 toc14
STARTUP WAVEFORMS FAST TURN-ON
MAX5918/19 toc15
2V/div 26mV STEP VSENSE 100mV/div VGATE 5V/div 1ms/div 5.0V 400ns/div 5.0V 1ms/div 5.0V, RSENSE 10m, RTIM 27k, CBOARD 1000µF tSCD VPGOOD 5V/div tFCD 125mV STEP VSENSE 100mV/div VGATE 5V/div IOUT 5A/div VOUT 5V/div VGATE 5V/div VPGOOD 5V/div VPGOOD 2V/div
STARTUP WAVEFORMS SLOW TURN-ON
MAX5918/19 toc16
AUTORETRY DELAY
MAX5918/19 toc17
2V/div VPGOOD 2V/div IOUT 5A/div VOUT 5V/div VGATE 5V/div 1ms/div 5.0V, RSENSE 10m, RTIM 47k, CBOARD 1000µF, CGATE 22nF 40ms/div 5.0V, RSENSE 10m, RTIM 47k, CBOARD 1000µF, RBOARD VOUT 5V/div IOUT 5A/div VGATE 5V/div
Low-Voltage, Dual Hot-Swap Controllers with Independent ON/OFF Control MAX5918/MAX5919
Description
NAME FUNCTION Channel Status Output (Open Drain, Absolute Maximum Ratings). PGOOD1 asserts high when PGOOD1 swap successful channel within regulation. PGOOD1 asserts during startup, when low, when channel off, when channel fault condition. SENSE1 GATE1 LIM1 MON1 MON2 LIM2 GATE2 SENSE2 Startup Timer Setting. Connect resistor from startup period. Leave unconnected default startup period 9ms. Channel Supply Input. Connect supply voltage 13.2V. Channel Current-Sense Input. Connect RSENSE1 from SENSE1. Connect disable circuit breaker function channel Channel Gate-Drive Output. Connect gate external N-channel MOSFET. Ground Channel Current-Limit Setting. Connect resistor from LIM1 current trip level. Connect default 25mV threshold (see Slow-Comparator Threshold, RLIM section). Channel Output-Voltage Monitor. Window comparator input. Connect through resistive-divider from OUT1 channel overvoltage undervoltage threshold. Connect disable. Channel Output-Voltage Monitor. Window comparator input. Connect through resistive-divider from OUT2 channel overvoltage undervoltage threshold. Connect disable. Channel Current-Limit Setting. Connect resistor from LIM2 current trip level. Connect default 25mV threshold (see Slow-Comparator Threshold, RLIM section). Channel On/Off Control Input. Channel turned when VON1 0.875V. Channel Gate-Drive Output. Connect gate external N-channel MOSFET. Channel Current-Sense Input. Connect RSENSE2 from SENSE2. Connect disable circuit breaker function channel Channel Supply Input. Connect supply voltage 13.2V. Channel On/Off Control Input. Channel turned when VON2 0.875V.
Channel Status Output (Open Drain, Absolute Maximum Ratings). PGOOD2 asserts high when PGOOD2 swap successful channel within regulation. PGOOD2 asserts during startup, when VON2 low, when channel off, when channel fault condition.
Detailed Description
MAX5918 MAX5919 circuit breaker hot-swap applications where line card inserted into live backplane. MAX5918 MAX5919 operate down provided inputs above 2.7V. Normally, when line card plugged into live backplane, card's discharged filter capacitors provide impedance that momentarily cause main power supply collapse. MAX5918 MAX5919 reside either backplane removable card provide inrush current limiting short-circuit protection. This achieved using external N-channel MOSFETs, external current-sense resistors, on-chip comparators. startup period currentlimit threshold MAX5918/MAX5919
adjusted with external resistors. Figure shows MAX5918/MAX5919 functional diagram. MAX5918/MAX5919 pull both PGOODs both external FETs overcurrent condition. MAX5918 also pulls both PGOODs both external FETs (protection) undervoltage/overvoltage fault, whereas, MAX5919 ONLY pulls corresponding fault channel's PGOOD (monitoring). When overvoltage/undervoltage fault disappears MAX5919, corresponding PGOOD automatically goes high impedance.
Figure Functional Diagram
RLIM1 LIM1 VFS, VFS, VSC, RSENSE2 FAST COMP. UVLO 2.4V TIMING OSCILLATOR SLOW COMP. GATE2 CHARGE PUMP DEVICE CONTROL LOGIC CURRENT CONTROL STARTUP LOGIC CURRENT CONTROL STARTUP LOGIC CHARGE PUMP OUT2 FAST DISCHARGE FAST DISCHARGE 100µA 687mV 0.875V 687mV MON2 2.4V SLOW COMP. UVLO BIAS REFERENCES FAST COMP. SENSE2 LIM2 RLIM2 543mV STARTUP LOGIC BLOCKS STARTUP LOGIC BLOCKS 543mV MAX5918/ MAX5919 STARTUP OSCILLATOR CHARGE-PUMP OSCILLATOR RTIM PGOOD1 PGOOD2
VSC,
RSENSE1
SENSE1
GATE1
OUT1
Low-Voltage, Dual Hot-Swap Controllers with Independent ON/OFF Control
MAX5918/MAX5919
MON1
Low-Voltage, Dual Hot-Swap Controllers with Independent ON/OFF Control MAX5918/MAX5919
Startup Period
RTIM sets duration startup period from 0.4ms 50ms (see Setting Startup Period, RTIM section). default startup period fixed when floating. startup period begins after following three conditions met: VIN1 VIN2 exceeds UVLO threshold (2.4V) UVLO startup delay (37.5ms). VON1 VON2 exceed threshold (0.875V). device latched autoretry delay (see Latched Autoretry Overcurrent Fault Management section). MAX5918/MAX5919 limit load current overcurrent fault occurs during startup instead completely turning external MOSFETs. slow comparator disabled during startup period load current limited ways: Slowly enhancing MOSFETs limiting MOSFET gate-charging current. Limiting voltage across external currentsense resistor. During startup period gate-drive current limited 100µA decreases with increase gate voltage (see Typical Operating Characteristics). This allows controller slowly enhance MOSFETs. fast comparator detects overcurrent, MAX5918/MAX5919 regulate gate voltage ensure that voltage across sense resistor does exceed VSU,TH. This effectively regulates inrush current during startup. Figure shows startup waveforms. PGOOD_ goes high impedance 0.75ms after startup period fault condition present.
VariableSpeed/BiLevel Fault Protection
VariableSpeed/BiLevel fault protection incorporates comparators with different thresholds response times monitor load current (Figure During startup period, protection provided limiting load current. Protection provided normal operation (after startup period expired) discharging both MOSFET gates with strong pulldown current response fault condition. After fault, PGOOD_ pulled low, MAX5918L MAX5919L stay latched MAX5918A MAX5919A automatically restart Slow-Comparator Startup Period slow comparator disabled during startup period while external MOSFETs turning Disabling slow comparator allows device ignore higher-than-normal inrush current charging board capacitors when card first plugged into live backplane. Slow-Comparator Normal Operation After startup period complete, slow comparator enabled device enters normal operation. comparator threshold voltage (VSC,TH) adjustable from 25mV 100mV. slow-comparator response
PGOOD tSTART tPGDLY VGATE SLOW COMPARATOR
4.3V 5.8V TURN-OFF TIME FAST COMPARATOR
VOUT VGATE VOUT VSU,TH RSENSE CBOARD ILOAD CBOARD LARGE
110µs 260ns
VSC,TH
VFC,TH VSC,TH)
SENSE VOLTAGE (VIN VSENSE)
Figure Startup Waveform
Figure VariableSpeed/BiLevel Response
Low-Voltage, Dual Hot-Swap Controllers with Independent ON/OFF Control
time decreases minimum 100µs with large overdrive voltage. Response time overdrive. variable speed response time allows MAX5918/MAX5919 ignore low-amplitude momentary glitches, thus increasing system noise immunity. After extended overcurrent condition, fault generated, both PGOODS pulled MOSFET gates discharged with strong pulldown current. Fast-Comparator Startup Period During startup period, fast comparator regulates gate voltage ensure that voltage across sense resistor does exceed startup fast-comparator threshold voltage (VSU,TH), VSU,TH scaled times slow-comparator threshold (VSC,TH). Fast-Comparator Normal Operation normal operation, load current reaches fastcomparator threshold, fault generated, both PGOODS pulled low, MOSFET gates discharged with strong pulldown current. This happens event serious current overload dead short. fast-comparator threshold voltage (VFC,TH) scaled four times slow-comparator threshold (VSC,TH). This comparator fast response time 260ns (Figure startup period begin immediately toggling supply voltages below/above UVLO threshold. When toggling supply voltage clear fault, remember that supply voltage must below then above UVLO threshold least 100µs regardless final value supply voltage.
MAX5918/MAX5919
Output Overvoltage/Undervoltage Fault Management
MAX5918/MAX5919 monitor output voltages with MON1 MON2 window comparator inputs. These voltage monitors enabled after startup period. Once enabled, voltage monitor detects fault VMON_ less than 543mV greater than 687mV. When MAX5918 protection device detects output overvoltage/undervoltage fault either MON1 MON2, both external MOSFET gates discharged both PGOODs pull low. MAX5918A, part continuously attempts restart after each autoretry period. part successfully restarts after fault removed after waiting autoretry period. MAX5918L, GATEs latched until output voltage fault removed fault latch cleared toggling cycling supply voltages above/below UVLO threshold. When MAX5919 monitoring device detects output overvoltage/undervoltage fault either MON1 MON2, neither external MOSFET gates affected, PGOOD channel experiencing fault pulls low. Thus fault reported channel with problem, MAX5919 does allow output overvoltage/undervoltage fault disrupt operation shutting down channels. MAX5919's PGOOD output immediately goes high impedance after output overvoltage/undervoltage fault removed. voltage monitors react output glitches less than 20µs. capacitor from MON_ increases effective glitch filter time. voltage monitoring function MAX5918/MAX5919 disabled connecting VIN1 MON1 VIN2 MON2.
Undervoltage Lockout (UVLO)
UVLO prevents MAX5918/MAX5919 from turning external MOSFETs until input voltage exceeds UVLO threshold (2.4V) tD,UVLO. MAX5918/MAX5919 power from higher input voltage rail charge pumps. This allows more efficient charge-pump operation. UVLO protects external MOSFETs from insufficient gate-drive voltage. tD,UVLO ensures that board fully inserted into backplane that input voltages stable. input voltage transient both supplies below UVLO threshold reinitiates tD,UVLO startup period.
Latched Autoretry Overcurrent Fault Management
MAX5918L/MAX5919L latch external MOSFETs when overcurrent fault detected. Toggling below 0.875V supply voltages below/above UVLO threshold least 100µs clears fault latch reinitiates startup period. Similarly, MAX5918A/MAX5919A turn external MOSFETs when overcurrent fault detected, then automatically restart after autoretry delay that internally times tSTART. During autoretry delay, toggling below 0.875V does clear fault latch. autoretry overridden, causing
Status Outputs (PGOOD_)
status output open-drain output that pulls response following conditions: Overcurrent fault Output undervoltage/overvoltage fault PGOOD_ goes when corresponding channel forced (ON_ 0.875V) (Table
Low-Voltage, Dual Hot-Swap Controllers with Independent ON/OFF Control MAX5918/MAX5919
Table Status Output Truth Table
PART OVERCURRENT FAULT (VOUT1) OVERCURRENT FAULT (VOUT2) OVER/UNDERVOLTAGE FAULT (VOUT1) OVER/UNDERVOLTAGE FAULT (VOUT2) PGOOD1/ PGOOD2 LOW/LOW LOW/LOW LOW/LOW LOW/LOW LOW/LOW LOW/LOW LOW/HIGH HIGH/LOW GATE1/ GATE2 OFF/OFF OFF/OFF OFF/OFF OFF/OFF OFF/OFF OFF/OFF ON/ON ON/ON
MAX5918 UV/OV Protection MAX5919 UV/OV Monitor
Applications Information
Component Selection
N-Channel MOSFET Select external MOSFETs according application's current levels. Table lists some recommended components. MOSFET's on-resistance DS(ON)) should chosen enough have minimum voltage drop full load limit MOSFET power dissipation. High RDS(ON) causes output ripple there pulsating load. Determine device power rating accommodate short-circuit condition board startup when device automatic-retry mode (see MOSFET Thermal Considerations section). Using MAX5918L/MAX5919L latched mode allows MOSFETs with lower power ratings. MOSFET typically withstands single-shot pulses with higher dissipation than specified package rating. Table lists some recommended manufacturers components.
Sense Resistor slow-comparator threshold voltage adjustable from 25mV 100mV. Select sense resistor that causes drop equal slow-comparator threshold voltage current level above maximum normal operating current. Typically, overload current times full load current. fast-comparator threshold four times slow-comparator threshold normal operating mode. Choose sense resistor power rating greater than (IOVERLOAD)2 VSC,TH. Slow-Comparator Threshold, RLIM slow-comparator threshold voltage adjustable from 25mV 100mV, allowing designers fine-tune current-limit threshold with standard-value sense resistors. slow-comparator thresholds allow increased efficiency reducing power dissipated sense resistor. Furthermore, 25mV slow-comparator threshold beneficial when operating with supply rails down because allows small percentage overall output voltage used current sensing. VariableSpeed/BiLevel fault protection feature offers inherent system immunity against load transients noise. This allows slow-comparator threshold close maximum normal operating level without experiencing nuisance faults. adjust slow-comparator threshold calculate RLIM follows: 25mV RLIM 0.25µA where desired slow-comparator threshold voltage. Setting Startup Period, RTIM startup period (tSTART) adjustable from 0.4ms 50ms. adjustable startup period feature allows sys-
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,
Low-Voltage, Dual Hot-Swap Controllers with Independent ON/OFF Control MAX5918/MAX5919
Table Component Manufacturers
COMPONENT Sense Resistors Fairchild MOSFETs International Rectifier Motorola MANUFACTURER Dale-Vishay PHONE 402-564-3131 704-264-8861 888-522-5372 310-233-3331 602-244-3576 WEBSITE www.vishay.com www.irctt.com www.fairchildsemi.com www.irf.com www.mot-sps.com/ppd
tems customized MOSFET gate capacitance board capacitance (CBOARD). startup period adjusted with resistance connected from (RTIM). RTIM must between 500k. startup period default value when left floating. Calculate RTIM with following equation: START RTIM 800pF where tSTART desired startup period.
Startup Sequence
There ways completing startup sequence. Case describes startup sequence that slowly turns MOSFETs limiting gate charge. Case uses current-limiting feature turns MOSFETs fast possible while still preventing high inrush current. output voltage ramp-up time (tON) determined longer timings, case case startup timer tSTART longer than guarantee enough time output voltage settle.
Case Slow Turn-On (without current limit) There ways turn MOSFETs without reaching fast-comparator current limit: board capacitance BOARD) small, inrush current low. gate capacitance high, MOSFETs turn slowly. both cases, turn-on time determined only charge required enhance MOSFET. small gate-charging current 100µA effectively limits output voltage dV/dt. Connecting external capacitor between GATE extends turn-on time. time required charge/discharge MOSFET follows: CGATE VGATE QGATE IGATE
RSENSE
VOUT CBOARD
where: GATE external gate ground capacitance (Figure VGATE change gate voltage. QGATE MOSFET total gate charge. IGATE gate-charging/discharging current. this case, inrush current depends MOSFET gate-to-drain capacitance (Crss) plus additional capacitance from GATE (CGATE), load current (ILOAD) present during startup period. IINRUSH CBOARD IGATE ILOAD Crss CGATE
RPULLUP SENSE GATE CGATE
PGOOD_
MAX5918 MAX5919
OPTIONAL COMPONENTS. COMPARATORS SECTION.
Example: Charging Discharging times using Fairchild FDB7030L MOSFET VIN1 then GATE1 charges 10.4V (VIN1 VDRIVE), therefore VGATE 10.4V. manufacturer's data sheet specifies that FDB7030L approximately 60nC gate charge Crss 600pF. MAX5918/MAX5919 have 100µA gate-charging current strong discharging current.
Figure Operating with External Gate Capacitor
Low-Voltage, Dual Hot-Swap Controllers with Independent ON/OFF Control MAX5918/MAX5919
CBOARD load does draw current during startup period. With gate capacitor inrush current, charge, discharge times are: IINRUSH 100µA 600pF 10.4V 60nC CHARGE 0.6ms 100µA 10.4V 60nC tDISCHARGE 0.02ms inputs with delay least 20µs. This allows internal cicuits stablilize after application steeply rising VIN_.
Using MAX5918/MAX5919 Backplane
Using MAX5918/MAX5919 backplane allows multiple cards with different input capacitance inserted into same slot even card does have on-board hot-swap protection. startup period triggered connected through trace card (Figure
With 22nF gate capacitor inrush current, charge, discharge times are: IINRUSH 100µA 26.5mA 600pF 22nF 22nF 10.4V 60nC CHARGE 2.89ms 100µA 22nF 10.4V 60nC tDISCHARGE 0.096ms
Input Transients
voltage must above UVLO during inrush fault conditions. When short-circuit condition occurs board, fast comparator trips causing external MOSFET gates discharged 3mA. main system power supply must able sustain temporary fault current, without dropping below UVLO threshold 2.4V, until external MOSFET completely off. main system power supply collapses below UVLO, MAX5918/ MAX5919 force device restart once supply recovered. MOSFET turned very short time resulting high di/dt. backplane delivering power external card must have inductance minimize voltage transients caused this high di/dt.
Case Fast Turn-On (with current limit) applications where board capacitance (CBOARD) high, inrush current causes voltage drop across SENSE that exceeds startup fast-comparator threshold. fast comparator regulates voltage across sense resistor VSU,TH. This effectively regulates inrush current during startup. this case, current charging CBOARD considered constant turn-on time CBOARD RSENSE VSU,TH
MOSFET Thermal Considerations
During normal operation, external MOSFETs dissipate little power. MOSFET RDS(ON) when MOSFET fully enhanced. power dissipated normal operation ILOAD2 RDS(ON). most power dissipation occurs during turn-on turnoff transients when MOSFETs their linear regions. Take into consideration worst-case scenario continuous short-circuit fault, consider these cases: single turn-on with device latched after fault (MAX5918L/MAX5919L) continuous automatic retry after fault (MAX5918A/MAX5919A) MOSFET manufacturers typically include package thermal resistance from junction ambient (RJA) thermal resistance from junction case (RJC), which determine startup time retry duty cycle tSTART/tSTART tRETRY). Calculate required transient thermal resistance with following equation:
maximum inrush current this case IINRUSH VSU,TH RSENSE
Figure shows waveforms timing diagrams startup transient with current regulation (see Typical Operating Characteristics). When operating under this condition, external gate capacitor required.
Comparators
comparators control on/off function MAX5918/MAX5919. allows independent control over channel channel Drive high 0.875V) enable channel channel respectively. Pull 0.875V) disable respective channel. time delay must added
Low-Voltage, Dual Hot-Swap Controllers with Independent ON/OFF Control
JA(MAX) JMAX ISTART
where ISTART VSU,TH RSENSE
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 MAX5918/ MAX5919 close card's connector. ground plane minimize impedance inductance. Minimize current-sense resistor trace length 10mm), ensure accurate current sensing with Kelvin connections (Figure
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 (refer MAX5919 Kit).
MAX5918/MAX5919
Chip Information
TRANSISTOR COUNT: 3542 PROCESS: BiCMOS
Selector Guide
PART MAX5918AEEE MAX5918LEEE MAX5919AEEE MAX5919LEEE OUTPUT UNDERVOLTAGE/OVERVOLTAGE PROTECTION/MONITOR Protection Protection Monitor Monitor FAULT MANAGEMENT Autoretry Latched Autoretry Latched
BACKPLANE
REMOVABLE CARD WITH HOT-INSERTION PROTECTION VOUT CBOARD
HIGH-CURRENT PATH
SENSE RESISTOR
SENSE_ GATE_ MAX5918 MAX5919
MAX5918 MAX5919
Figure Kelvin Connection Current-Sense Resistors
OPTIONAL COMPONENTS. COMPARATORS SECTION.
Figure Using MAX5918/MAX5919 Backplane
Low-Voltage, Dual Hot-Swap Controllers with Independent ON/OFF Control MAX5918/MAX5919
Typical Operating Circuit
VIN1 PGOOD1 PGOOD2 PGOOD1 PGOOD2 SENSE2 GATE2 LIM2 VIN2 LIM1 MON1 SENSE1 GATE1 CBOARD1 VOUT1
MAX5918/ MAX5919
MON2
CBOARD2 VOUT2 *OPTIONAL
Low-Voltage, Dual Hot-Swap Controllers with Independent ON/OFF Control
Package Information
(The package drawing(s) this data sheet reflect most current specifications. latest package outline information, www.maxim-ic.com/packages.)
QSOP.EPS
MAX5918/MAX5919
PACKAGE OUTLINE, QSOP .150", .025" LEAD PITCH
21-0055
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 2004 Maxim Integrated Products Printed registered trademark Maxim Integrated Products.
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