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MAX5955AEEE+maxim ?N/a350avaiLow-Voltage, Dual Hot-Swap Controllers with Independent On/Off Control
MAX5955AEEE+maximN/a350avaiLow-Voltage, Dual Hot-Swap Controllers with Independent On/Off Control
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MAX5955AEEE+T |MAX5955AEEETMAXIMN/a1000avaiLow-Voltage, Dual Hot-Swap Controllers with Independent On/Off Control
MAX5955BUEE+T |MAX5955BUEETMAXIMN/a593avaiLow-Voltage, Dual Hot-Swap Controllers with Independent On/Off Control
MAX5956AEEEMAXN/a6avaiLow-Voltage, Dual Hot-Swap Controllers with Independent On/Off Control
MAX5956AEEEMAXIMN/a21avaiLow-Voltage, Dual Hot-Swap Controllers with Independent On/Off Control
MAX5956AEEE+T |MAX5956AEEETMAXIMN/a2395avaiLow-Voltage, Dual Hot-Swap Controllers with Independent On/Off Control


MAX5956AEEE+T ,Low-Voltage, Dual Hot-Swap Controllers with Independent On/Off ControlELECTRICAL CHARACTERISTICS(V = +1V to +13.2V provided at least one supply is higher than +2.7V, V = ..
MAX5961ETM+T ,0 to 16V, Quad, Hot-Swap Controller with 10-Bit Current and Voltage Monitor MAX5961ETM+ RELIABILITY REPORT FOR MAX5961ETM+ PLASTIC ENCAPSULAT ..
MAX5969AETB+ ,IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFETELECTRICAL CHARACTERISTICS(V = (V - V ) = 48V, R = 24.9kω, R = 619ω. RTN, WAD, PG, and 2EC unconnec ..
MAX5969BETB+T ,IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFETFeaturesS IEEE 802.3af/at CompliantThe MAX5969A/MAX5969B provide a complete interface ® S 2-Event C ..
MAX5976BETE+T ,2.7V to 18V, 7A, Hot-Swap SolutionsApplicationsNote: All devices are specified over the -40°C to +85°C operating temperature range.RAI ..
MAX5977AETP+ ,1V to 16V, Single-Channel, Hot-Swap Controllers with Precision Current-Sensing OutputApplicationsturn-off and a lower slow-trip threshold for a delayed turn-off.ServersExceeding either ..
MAZ8180-H ,Silicon planar typeElectrical characteristics within part numbers T = 25°CaTemperaturecoefficient ofZener voltage Rev ..
MAZ8180-L ,Silicon planar typeAbsolute Maximum Ratings T = 25°CaMarking SymbolParameter Symbol Rating UnitRefer to the list of t ..
MAZ8180-M ,Silicon planar typeelectrical characteristicsZ Zwithin part numbersReverse current I V ··············· Specified value ..
MAZ8200G ,Silicon planar typeElectrical Characteristics T = 25°C±3°CaParameter Symbol Conditions Min Typ Max UnitForward voltag ..
MAZ8200G ,Silicon planar typeAbsolute Maximum Ratings T = 25°CaParameter Symbol Rating UnitRepetitive peak forward current I 20 ..
MAZ8200-H ,Silicon planar typeFeatures•Extremely low noise voltage caused from the diode (2.4V to 39V,1/3 to 1/10 of our conventi ..


MAX5955AEEE+-MAX5955AEEE+T-MAX5955BUEE+T-MAX5956AEEE-MAX5956AEEE+T
Low-Voltage, Dual Hot-Swap Controllers with Independent On/Off Control
General Description
The MAX5955 and MAX5956 are +1V to +13.2V dual
hot-swap controllers with independent on/off control for
complete protection of dual-supply systems. They allow
the safe insertion and removal of circuit cards into live
backplanes. The MAX5955 and MAX5956 operate
down to 1V provided one of the inputs is above 2.7V.
The discharged filter capacitors of the circuit card pro-
vide low impedance to the live backplane. High inrush
currents from the backplane to the circuit card can burn
up connectors and components, or momentarily collapse
the backplane power supply leading to a system reset.
The MAX5955 and MAX5956 hot-swap controllers pre-
vent such problems by gradually ramping up the output
voltage and regulating the current to a preset limit when
the board is plugged in, allowing the system to stabilize
safely. After the startup cycle is completed, two on-chip
comparators provide VariableSpeed/BiLevel™ protection
against short-circuit and overcurrent faults, as well as
immunity against system noise and load transients. In the
event of a fault condition, the load is disconnected. The
MAX5955B and MAX5956B must be unlatched after a
fault, and the MAX5955A and MAX5956A automatically
restart after a fault.
The MAX5955 and MAX5956 integrate an on-board
charge pump to drive the gates of low-cost, external n-
channel MOSFETs. The devices offer integrated fea-
tures like startup current regulation and current glitch
protection to eliminate external timing resistors and
capacitors. These devices provide open-drain status
outputs, an adjustable startup timer, and adjustable
current limits. The MAX5955 provides output undervolt-
age/overvoltage protection for each channel, while the
MAX5956 provides undervoltage/overvoltage monitor-
ing for each channel.
The MAX5955 and MAX5956 are available in a space-
saving 16-pin QSOP package.
Applications
Features
Safe Hot Swap for +1V to +13.2V Power Supplies
with VIN1or VIN2≥2.7V
Independent On/Off Control for Each ChannelInternal Charge Pumps Generate n-Channel
MOSFET Gate Drives
Inrush Current Regulated at StartupCircuit-Breaker FunctionAdjustable Circuit Breaker/Current-Limit
Threshold from 25mV to 100mV
VariableSpeed/BiLevel Circuit Breaker ResponseAutoretry or Latched Fault ManagementStatus Outputs Indicate Fault/Safe ConditionOutput Undervoltage and Overvoltage Monitoring
or Protection
MAX5955/MAX5956
Low-Voltage, Dual Hot-Swap
Controllers with Independent On/Off Control
Ordering Information

PGOOD1PGOOD2
ON2
IN2
SENSE2
GATE2
ON1
LIM2
MON2
TOP VIEW
MAX5955
MAX5956
TIM
IN1
GND
SENSE1
GATE1
LIM1
MON1
Pin Configuration

19-3813; Rev 0; 9/05
EVALUATION KIT
AVAILABLE
PARTTEMP RANGEPIN-PACKAGE
MAX5955AEEE
-40°C to +85°C16 QSOP
MAX5955AEEE+-40°C to +85°C16 QSOP
MAX5955AUEE 0°C to +85°C16 QSOP
MAX5955AUEE+ 0°C to +85°C16 QSOP
MAX5955BEEE-40°C to +85°C16 QSOP
MAX5955BEEE+-40°C to +85°C16 QSOP
MAX5955BUEE 0°C to +85°C16 QSOP
MAX5955BUEE+ 0°C to +85°C16 QSOP
+Denotes lead-free package.
Ordering Information continued at end of data sheet.
Selector Guide and Typical Operating Circuit appear at end
of data sheet.

Base Station Line Cards
Network Switches,
Routers, Hubs
Solid-State Circuit
Breakers
RAID
Power-Supply Sequencing
Hot Plug-In Daughter
Cards
Portable Computer Device
Bays (Docking Stations)
MAX5955/MAX5956
Low-Voltage, Dual Hot-Swap Controllers with
Independent On/Off Control
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS

(VIN_= +1V to +13.2V provided at least one supply is higher than +2.7V, VON1= VON2= +2.7V, TA= TMINto TMAX, unless otherwise
noted. Typical values are at VIN1= +5V, VIN2= +3.3V, and TA= +25°C.) (Note 1)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
IN_ to GND...........................................................................+14V
GATE_ to GND...........................................-0.3V to (VIN_+ 6.2V)
ON_, PGOOD_, TIM to GND.......................-0.3V to the higher of
(VIN1+ 0.3V) and (VIN2+ 0.3V)
SENSE_, MON_, LIM_ to GND...................-0.3V to (VIN_+ 0.3V)
Current into Any Pin .........................................................±50mA
Continuous Power Dissipation (TA= +70°C)
16-Pin QSOP (derate 8.3mW/°C above +70°C)...........667mW
Operating Temperature Range
MAX59_ _ _U_ _...................................................0°C to +85°C
MAX59_ _ _E_ _................................................-40°C to +85°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
POWER SUPPLIES

IN_ Input Voltage RangeVINOther VIN ≥ +2.7V1.013.2V
Supply CurrentIINIIN1 + IIN2, VIN1 = +5V, VIN2 = +3.3V1.22.3mA
CURRENT CONTROL

TA = +25°C22.52527.5LIM = GNDTA = -40°C to +85°C20.527.5Slow-Comparator Threshold
(VIN_ - VSENSE_) (Note 2)VSC,TH
RLIM = 300kΩ80100130
1mV overdrive3msSlow-Comparator Response Time
(Note 3)tSCD10mV overdrive110µs
VSU,THDuring startup2 x VSC,THFast-Comparator Threshold
(VIN_ - VSENSE_)VFC,THVIN_ - VSENSE_; normal operation4 x VSC,THmV
Fast-Comparator Response Time
(VIN_ - VSENSE_)tFCD10mV overdrive, from overload condition260ns
SENSE Input Bias CurrentIB SENSEVSENSE_ = VIN_0.031µA
MOSFET DRIVER

RTI M = 100kΩ 610.816
RTIM = 4kΩ (minimum value)0.310.450.58Startup Period (Note 4)tSTART
TIM floating4917har g i ng , V GATE _ = + 5V , V IN _ = + 10V ( N ote 5) 65100130µA
Average Gate CurrentIGATEDischarging, triggered by a fault or when
VON_ < 0.875V3mA
VIN_ = 3V to 13.2V4.85.46.0Gate-Drive VoltageVDRIVEVGATE_ - VIN_,
IGATE_ < 1µAVIN_ = 2.7V to 3.0V4.15.06.0V
ON_ COMPARATOR

Low to high0.850.8750.90VON_ ThresholdVON_,THHysteresis25mV
ON_ Propagation Delay10mV overdrive50µs
MAX5955/MAX5956
Low-Voltage, Dual Hot-Swap Controllers with
Independent On/Off Control
ELECTRICAL CHARACTERISTICS (continued)

(VIN_= +1V to +13.2V provided at least one supply is higher than +2.7V, VON1= VON2= +2.7V, TA= TMINto TMAX, unless otherwise
noted. Typical values are at VIN1= +5V, VIN2= +3.3V, and TA= +25°C.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS

VON_ < 4.5V0.03
VON_ > 4.5V100ON_ Input Bias CurrentIBONVIN1 = VIN2 = +13.2V
VON_ = 4.5V0.031
ON_ Pulse-Width LowtUNLATCHTo unlatch after a latched fault100µs
DIGITAL OUTPUT (PGOOD_)

Output Leakage CurrentVPGOOD_ = 13.2V1µA
Output Voltage LowVOLISINK = 1mA0.4V
PGOOD_ DelaytPGDLYAfter tSTART, MON_ = VIN_0.75ms
OUTPUT VOLTAGE MONITORS (MON1, MON2)

Overvoltage657687707MON_ Trip ThresholdVMONUndervoltage513543563mV
MON_ Glitch Filter20µs
MON_ Input Bias CurrentVMON_ = 600mV0.03µA
UNDERVOLTAGE LOCKOUT (UVLO)

Startup is initiated when this threshold is
reached by VIN1 or VIN2, VON_ > 0.875V2.102.42.67VUVLO ThresholdVUVLO
Hysteresis100mV
UVLO Glitch Filter Reset TimeVIN_ toggled below UVLO to unlatch after a
fault100µs
UVLO to Startup DelaytD,UVLOVIN_ step from 0 to 2.8V2037.566ms
SHUTDOWN LATCH/RESTART

Autoretry DelaytRETRYDelay time to restart after fault shutdown64 x tSTARTms
Note 1:
All devices are 100% tested at TA= +25°C and TA= +85°C. Limits at TA= 0°C and -40°C are guaranteed by design.
Note 2:
The MAX5955/MAX5956 slow-comparator threshold is adjustable. VSC,TH= RLIM✕0.25µA + 25mV (see the Typical
Operating Characteristics).
Note 3:
The current-limit slow-comparator response time is weighted against the amount of overcurrent; the higher the overcurrent
condition, the faster the response time (see the Typical Operating Characteristics).
Note 4:
The startup period (tSTART) is the time during which the slow comparator is ignored and the device acts as a current-limiter
by regulating the sense current with the fast comparator (see the Startup Periodsection).
Note 5:
The current available at GATE is a function of VGATE(see the Typical Operating Characteristics).
MAX5955/MAX5956
Low-Voltage, Dual Hot-Swap Controllers with
Independent On/Off Control

SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX5955/56 toc01
VINX (V)
IIN
(mA)
VINY = VON1 = VON2 = 2.7V
IINX + IINY
IINX
IINY
TOTAL SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX5955/56 toc02
VINX (V)
IIN
(mA)
VINY = 5.0V
A) VON1 = VON2 = 3.3V
B) VON1 = VON2 = 1.5V
C) VON1 = VON2 = 0
SUPPLY CURRENT
vs. TEMPERATURE
MAX5955/56 toc03
TEMPERATURE (°C)
IIN
(mA)
VON1 = VIN1
VON2 = VIN2IIN1 + IIN2
IIN2
IIN1824101214
GATE-DRIVE VOLTAGE
vs. INPUT VOLTAGE

MAX5955/56 toc04
VINX (V)
GATE-DRIVE VOLTAGE (V)
VINY = 2.7V
GATE CHARGE CURRENT
vs. GATE VOLTAGE
MAX5955/56 toc05
VGATEX (V)
GATE CHARGE CURRENT (
VINY = 2.7V
VINX = 13.2V
VINX = 5V
VINX = 1V
GATE CHARGE CURRENT
vs. TEMPERATURE
MAX5955/56 toc06
TEMPERATURE (°C)
GATE CHARGE CURRENT (VINX = 13.2V
VINX = 5V
VINX = 1V
VINY = 2.7V
VGATEX = 0
GATE STRONG DISCHARGE CURRENT
vs. GATE VOLTAGE
MAX5955/56 toc07
GATE DISCHARGE CURRENT (mA)
VINX = 13.2VVINX = 5V
VINX = 1V
VON1 = VON2 = 0
VINY = 2.7V
VGATEX = VINX + 6.2V
GATE STRONG DISCHARGE CURRENT
vs. TEMPERATURE
MAX5955/56 toc08
GATE DISCHARGE CURRENT (mA)
VINX = 13.2VVINX = 5V
VINX = 1V
VON1 = VON2 = 0
VINY = 2.7V
VGATEX = VINX + 6.2V
TURN-OFF TIME vs. SENSE VOLTAGE
MAX5955/56 toc09
TURN-OFF TIME (ms)
SLOW-COMP. THRESHOLD
FAST-COMP. THRESHOLD
Typical Operating Characteristics

(Typical Operating Circuits, Q1 = Q2 = Fairchild FDB7090L, VIN1= +5V, VIN2= +3.3V, VON1= VON2= +2.7V, TA= +25°C, unless
otherwise noted. Channels 1 and 2 are identical in performance. Where characteristics are interchangeable, channels 1 and 2 are
referred to as X and Y.)
MAX5955/MAX5956
Low-Voltage, Dual Hot-Swap Controllers with
Independent On/Off Control

TURN-OFF TIME vs. SENSE VOLTAGE
(EXPANDED SCALE)
MAX5955/56 toc10
VIN - VSENSE (mV)
TURN-OFF TIME (ms)
SLOW-COMP. THRESHOLD
SLOW-COMPARATOR THRESHOLD
vs. RLIM
MAX5955/56 toc11
RLIM (kΩ)
SC,TH
(mV)
STARTUP PERIOD vs. RTIM

RTIM (kΩ)
START
(ms)200300100400500600
VPGOOD
5V/div
VSENSE - VIN
100mV/div
VGATE
5V/div
TURN-OFF TIME
SLOW-COMPARATOR FAULT

MAX5955/56 toc13
1ms/div
VIN = 5.0V
tSCD
26mV STEPVPGOOD
5V/div
VSENSE - VIN
100mV/div
VGATE
5V/div
TURN-OFF TIME
FAST-COMPARATOR FAULT

MAX5955/56 toc14
400ns/div
VIN = 5.0V
tFCD
125mV STEP
VON
2V/div
VPGOOD
2V/div
IOUT
5A/div
VOUT
5V/div
VGATE
5V/div
STARTUP WAVEFORMS
FAST TURN-ON

MAX5955/56 toc15
1ms/div
VIN = 5.0V, RSENSE = 10mΩ,
RTIM = 27kΩ, CBOARD = 1000μF
VON
2V/div
VPGOOD
2V/div
IOUT
5A/div
VOUT
5V/div
VGATE
5V/div
STARTUP WAVEFORMS
SLOW TURN-ON

MAX5955/56 toc16
1ms/div
IOUT
5A/div
VOUT
5V/div
VGATE
5V/div
AUTORETRY DELAY

MAX5955/56 toc17
40ms/div
Typical Operating Characteristics (continued)

(Typical Operating Circuits, Q1 = Q2 = Fairchild FDB7090L, VIN1= +5V, VIN2= +3.3V, VON1= VON2= +2.7V, TA= +25°C, unless
otherwise noted. Channels 1 and 2 are identical in performance. Where characteristics are interchangeable, channels 1 and 2 are
referred to as X and Y.)
MAX5955/MAX5956
Detailed Description

The MAX5955 and MAX5956 are circuit breaker ICs for
hot-swap applications where a line card is inserted into
a live backplane. The MAX5955 and MAX5956 operate
down to 1V provided one of the inputs is above 2.7V.
Normally, when a line card is plugged into a live back-
plane, the card’s discharged filter capacitors provide
low impedance that can momentarily cause the main
power supply to collapse. The MAX5955 and MAX5956
reside either on the backplane or on the removable
card to provide inrush current limiting and short-circuit
protection. This is achieved by using external n-chan-
nel MOSFETs, external current-sense resistors, and two
on-chip comparators. The startup period and current-
limit threshold of the MAX5955/MAX5956 can be
adjusted with external resistors. Figure 1 shows the
MAX5955/MAX5956 functional diagram.
The MAX5955/MAX5956 pull both PGOODs low and
both external FETs off for an overcurrent condition. The
MAX5955 also pulls both PGOODs low and both external
FETs off (protection) for an undervoltage/overvoltage
fault, whereas, the MAX5956 ONLYpulls the corre-
sponding fault channel’s PGOOD_ low (monitoring).
When the overvoltage/undervoltage fault disappears on
the MAX5956, the corresponding PGOOD_ automatically
goes high impedance.
Low-Voltage, Dual Hot-Swap Controllers with
Independent On/Off Control
Pin Description
PINNAMEFUNCTION
PGOOD1
Channel 1 Status Output (Open Drain, see the Absolute Maximum Ratings). PGOOD1 asserts high when hot
swap is successful and channel 1 is within regulation. PGOOD1 asserts low during startup, when ON1 is
low, when channel 1 is off, or when channel 1 has any fault condition.TIMStartup Timer Setting. Connect a resistor from TIM to GND to set the startup period. Leave TIM unconnected
for the default startup period of 9ms.IN1Channel 1 Supply Input. Connect to a supply voltage of 1V to 13.2V.SENSE1Channel 1 Current-Sense Input. Connect RSENSE1 from IN1 to SENSE1. Connect to IN1 to disable circuit
breaker function of channel 1.GATE1Channel 1 Gate-Drive Output. Connect to the gate of an external n-channel MOSFET.GNDGroundLIM1Channel 1 Current-Limit Setting. Connect a resistor from LIM1 to GND to set the current trip level. Connect to
GND for the default 25mV threshold (see the Slow-Comparator Threshold, RLIM section).MON1Channel 1 Output-Voltage Monitor. Window comparator input. Connect through a resistive divider from
OUT1 to GND to set the channel 1 overvoltage and undervoltage threshold. Connect to IN1 to disable.MON2Channel 2 Output-Voltage Monitor. Window comparator input. Connect through a resistive divider from
OUT2 to GND to set the channel 2 overvoltage and undervoltage threshold. Connect to IN2 to disable.LIM2Channel 2 Current-Limit Setting. Connect a resistor from LIM2 to GND to set the current trip level. Connect to
GND for the default 25mV threshold (see the Slow-Comparator Threshold, RLIM section).ON1Channel 1 On/Off Control Input. Channel 1 is turned on when VON1 > 0.875V.GATE2Channel 2 Gate-Drive Output. Connect to the gate of an external n-channel MOSFET.SENSE2Channel 2 Current-Sense Input. Connect RSENSE2 from IN2 to SENSE2. Connect to IN2 to disable circuit-
breaker function of channel 2.IN2Channel 2 Supply Input. Connect to a supply voltage of 1V to 13.2V.ON2Channel 2 On/Off Control Input. Channel 2 is turned on when VON2 > 0.875V.PGOOD2
Channel 2 Status Output (Open Drain, see the Absolute Maximum Ratings). PGOOD2 asserts high when hot
swap is successful and channel 2 is within regulation. PGOOD2 asserts low during startup, when VON2 is
low, when channel 2 is off, or when channel 2 has any fault condition.
MAX5955/MAX5956
Low-Voltage, Dual Hot-Swap Controllers with
Independent On/Off Control

UVLO
AST COMP
SLOW COMP
AST DISCHARGE
OUT1
2.4V
2.4V
BIAS AND
REFERENCES
TIMING
OSCILLA
TOR
TUP
OSCILLA
TOR
TO ST
TUP
LOGIC BLOCKS
CHARGE
PUMP
DEVICE CONTROL
LOGIC
SC, TH
FS, TH
LIM1
SENSE1
IN1
TE1
SENSE1
LIM1
LIM2
3mA
687mV543mV
MON1
ON1
ON2
PGOOD2
PGOOD1
UVLO
FAST COMP
SLOW COMP
AST DISCHARGE
OUT2
CHARGE-PUMP
OSCILLA
TOR
TO ST
TUP
LOGIC BLOCKS
CHARGE
PUMP
CURRENT CONTROL
AND
TUP LOGIC
CURRENT CONTROL
AND
TUP LOGIC
SC, TH
FS, TH
SENSE2IN2GA
TE2
SENSE2
LIM2
3mA
687mV
543mV
MON2
MAX5955MAX5956
0.875V
TIM
TIM
MAX5955/MAX5956
Startup Period

RTIMsets the duration of the startup period from 0.45s
to 50ms (see the Setting the Startup Period, RTIMsec-
tion). The default startup period is fixed at 9ms when
TIM is floating. The startup period begins after the fol-
lowing three conditions are met:VIN1or VIN2exceeds the UVLO threshold (2.4V) for
the UVLO to startup delay (37.5ms).VON1and VON2exceed the ON threshold (0.875V).The device is not latched or in its autoretry delay (see
the Latched and Autoretry Overcurrent Fault
Managementsection).
The MAX5955/MAX5956 limit the load current if an
overcurrent fault occurs during startup instead of com-
pletely turning off the external MOSFETs. The slow
comparator is disabled during the startup period and
the load current can be limited in two ways:Slowly enhancing the MOSFETs by limiting the
MOSFET gate-charging current.Limiting the voltage across the external current-
sense resistor.
During the startup period the gate-drive current is limit-
ed to 100µA and decreases with the increase of the
gate voltage (see the Typical Operating Characteris-
tics). This allows the controller to slowly enhance the
MOSFETs. If the fast comparator detects an overcur-
rent, the MAX5955/MAX5956 regulate the gate voltage
to ensure that the voltage across the sense resistor
does not exceed VSU,TH. This effectively regulates the
inrush current during startup. Figure 2 shows the start-
up waveforms. PGOOD_ goes high impedance 0.75ms
after the startup period if no fault condition is present.
VariableSpeed/BiLevel Fault Protection

VariableSpeed/BiLevel fault protection incorporates two
comparators with different thresholds and response
times to monitor the load current (Figure 3). During the
startup period, protection is provided by limiting the
load current. Protection is provided in normal operation
(after the startup period has expired) by discharging
both MOSFET gates with a strong 3mA pulldown cur-
rent in response to a fault condition. After a fault,
PGOOD_ is pulled low, the MAX5955B and MAX5956B
stay latched off and the MAX5955A and MAX5956A
automatically restart.
Slow-Comparator Startup Period

The slow comparator is disabled during the startup
period while the external MOSFETs are turning on.
Disabling the slow comparator allows the device to
ignore the higher-than-normal inrush current charging
the board capacitors when a card is first plugged into a
live backplane.
Low-Voltage, Dual Hot-Swap Controllers with
Independent On/Off Control

tON
4.3V TO 5.8V
VGATE
VGATE
PGOOD
VTH
VOUT
VOUT
ILOAD
tSTART + tPGDLY
CBOARD = LARGE
CBOARD = 0
VSU,TH
RSENSE
Figure 2. Startup Waveform
SENSE VOLTAGE (VIN - VSENSE)
TURN-OFF TIME
VSC,THVFC,TH
(4 x VSC,TH)
3ms
110μs
260ns
SLOW
COMPARATOR
FAST
COMPARATOR
Figure 3. VariableSpeed/BiLevel Response
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