MAX4370ESA ,Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault ProtectionELECTRICAL CHARACTERISTICS(V = +2.7V to +13.2V, T = -40°C to +85°C, unless otherwise noted. Typical ..
MAX4370ESA ,Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protectionapplications using Maxim’sOperationDualSpeed/BiLevel™ detection. This controller,' Inrush Current R ..
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MAX4370ESA+ ,Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protectionapplications using Maxim’sOperationDualSpeed/BiLevel™ detection. This controller,♦ Inrush Current R ..
MAX4370ESA+T ,Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault ProtectionELECTRICAL CHARACTERISTICS(V = +2.7V to +13.2V, T = -40°C to +85°C, unless otherwise noted. Typical ..
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MAX817LCSA ,+5V microprocessor supervisory circuit. Reset threshold 4.65V, active-low reset, backup-battery switchover, power-fail comparator, watchdog input, battery freshness seal.applications. The MAX817/MAX818/MAX819 are specif-(MAX817/MAX818)ically designed to ignore fast tra ..
MAX817LCSA+ ,+5V Microprocessor Supervisory CircuitsELECTRICAL CHARACTERISTICS(V = +4.75V to +5.5V for MAX81_L, V = +4.5V to +5.5V for MAX81_M, V = 2.8 ..
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MAX817MCSA ,+5V microprocessor supervisory circuit. Reset threshold 4.40V, active-low reset, backup-battery switchover, power-fail comparator, watchdog input, battery freshness seal.Applications TOP VIEWBattery-Powered Computers and ControllersEmbedded Controllers OUT 1 8 BATTInte ..
MAX4370ESA
Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protection
General DescriptionThe MAX4370 is a circuit-breaker IC designed to offer
protection in hot-swap applications using Maxim’s
DualSpeed/BiLevel™ detection. This controller,
designed to reside either on the backplane or on the
removable card, is used to protect a system from start-
up damage when a card or board is inserted into a rack
with the main system power supply turned on. The
card’s discharged filter capacitors provide a low
impedance that can momentarily cause the main power
supply to collapse. The MAX4370 prevents this start-up
condition by providing inrush current regulation during
a programmable start-up period, allowing the system to
stabilize safely. In addition, two on-chip comparators
provide DualSpeed/BiLevel short-circuit protection and
overcurrent protection during normal operation.
The MAX4370 provides protection for a +3V to +12V
single supply. An internal charge pump generates the
controlled gate drive for an external N-channel MOS-
FET power switch. The MAX4370 latches the switch off
after a fault condition until an external reset signal
clears the device. Other features include a status pin to
indicate a fault condition, an adjustable overcurrent
response time, and a power-on reset comparator.
The MAX4370 is specified for the extended-industrial
temperature range (-40°C to +85°C) and is available in
an 8-pin SO package.
ApplicationsHot Board Insertion
Solid-State Circuit Breaker
FeaturesDualSpeed/BiLevel Protection During Normal
OperationInrush Current Regulated at Start-UpResides Either on the Backplane or on the
Removable CardProgrammable Start-Up Period and Response
TimeAllows Safe Board Insertion and Removal from
Live BackplaneProtection for +3V to +12V Single SuppliesLatched Off After Fault ConditionStatus Output PinInternal Charge Pump Generates Gate Drive for
External N-Channel MOSFET
MAX4370
Current-Regulating Hot-Swap Controller with
DualSpeed/BiLevel Fault Protectionypical Operating Circuit19-1472; Rev 0; 4/99
Ordering InformationDualSpeed/BiLevel is a trademark of Maxim Integrated Products.
Pin Configuration appears at end of data sheet.
MAX4370
Current-Regulating Hot-Swap Controller with
DualSpeed/BiLevel Fault Protection
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VIN= +2.7V to +13.2V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at VIN= +5V and TA= +25°C.) (Note 2)
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.
Note 1:ON can be pulled below ground. Limiting the current to 2mA ensures that this pin is never lower than about -0.8V.
VINto GND...........................................................................+15V
STAT to GND..........................................................-0.3V to +14V
GATE to GND..............................................-0.3V to (VIN+ 8.5V)
ON to GND (Note 1).................................................-1V to +14V
CSPD to GND.............-0.3V to the lower of (VIN+ 0.3V) or +12V
VSEN, CTIM to GND....................................-0.3V to (VIN+ 0.3V)
Current into ON...................................................................±2mA
Current into Any Other Pin................................................±50mA
Continuous Power Dissipation (TA= +70°C)
SO (derate 5.9mW/°C above +70°C)...........................471mW
Operating Temperature Range...........................-40°C to +85°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10sec)............................+300°C
MAX4370
Current-Regulating Hot-Swap Controller with
DualSpeed/BiLevel Fault Protection
ELECTRICAL CHARACTERISTICS (continued)(VIN= +2.7V to +13.2V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at VIN= +5V and TA= +25°C.) (Note 2)
Note 2:All devices are 100% tested at TA = +25°C. All temperature limits are guaranteed by design.
Note 3:The start-up 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. It is measured from ON rising above 0.6V to STAT rising.
Note 4:The current available at GATE is a function of VGATE(see TypicalOperating Characteristics.)
MAX4370
Current-Regulating Hot-Swap Controller with
DualSpeed/BiLevel Fault Protection
Typical Operating Characteristics(Circuit of Figure 7, VIN= 5V, RSENSE= 100mΩ, M1 = FDS6670A, CBOARD= 470µF, CGATE= 0, RS= 0, TA= +25°C, unless other-
wise noted.)
MAX4370
Current-Regulating Hot-Swap Controller with
DualSpeed/BiLevel Fault Protectionypical Operating Characteristics (continued)(Circuit of Figure 7, VIN= 5V, RSENSE= 100mΩ, M1 = FDS6670A, CBOARD= 470µF, CGATE= 0, RS= 0, TA= +25°C, unless other-
wise noted.)
Current-Regulating Hot-Swap Controller with
DualSpeed/BiLevel Fault Protectionypical Operating Characteristics (continued)(Circuit of Figure 7, VIN= 5V, RSENSE= 100mΩ, M1 = FDS6670A, CBOARD= 470µF, CGATE= 0, RS= 0, TA= +25°C, unless other-
wise noted.)
MAX4370
Current-Regulating Hot-Swap Controller with
DualSpeed/BiLevel Fault Protection
Pin DescriptionFigure 1. Functional Diagram
MAX4370
Current-Regulating Hot-Swap Controller with
DualSpeed/BiLevel Fault Protection
Detailed DescriptionThe MAX4370 is a circuit-breaker IC designed for hot-
swap applications where a card or board is to be
inserted into a rack with the main system power supply
turned on. Normally, when a card is plugged into a live
backplane, the card is discharged filter capacitors pro-
vide a low impedance, which can momentarily cause
the main power supply to collapse. The MAX4370 is
designed to reside either in the backplane or in the
removable card to provide inrush-current limiting and
short-circuit protection. This is achieved using a charge
pump as gate drive for an external N-channel MOSFET,
an external current-sense resistor, and two on-chip
comparators. Figure 1 shows the device’s functional
diagram.
The slow comparator response time and the start-up
timer can be adjusted with external capacitors. The tim-
ing components are optional; without them the part is
set to its nominal values, as shown in the Electrical
Characteristics.
Start-Up PeriodCTIM sets the start-up period. This mode starts when
the power is first applied to VINif ON is connected to
VIN, or at the rising edge of ON. In addition, the voltage
at VINmust be above the undervoltage lockout for
150ms (see Undervoltage Lockout).
During start-up, the slow comparator is disabled and
current limiting is provided two different ways:Slow ramping of the current to the load by controlling
the external MOSFET gate voltage.Limiting the current to the load by regulating the volt-
age across the external current-sense resistor.
Unlike other circuit-breaker ICs, the MAX4370 hot-swap
controller regulates the current to a preset level instead
of completely turning off if an overcurrent occurs during
start-up.
In start-up mode, the gate drive current is limited to
100µA and decreases with the increase of the gate
voltage (see Typical Operating Characteristics). This
allows the MAX4370 to slowly enhance the MOSFET. If
the fast comparator detects an overcurrent, the gate
voltage is momentarily discharged with a fixed 80µA
current until the load current through the sense resistor
(RSENSE) decreases below its threshold point. This
effectively regulates the turn-on current during start-up.
Figure 2 shows the start-up waveforms. STAT goes
high at the end of the start-up period if no fault condi-
tion is present.
Normal Operation (DualSpeed/BiLevel)In normal operation (after the start-up period has
expired), protection is provided by turning off the exter-
nal MOSFET when a fault condition is encountered.
DualSpeed/BiLevel fault protection incorporates two
comparators with different thresholds and response
times to monitor the load current:Slow Comparator. This comparator has an externally
set response time (20µs to seconds) and a fixed
50mV threshold voltage. The slow comparator
ignores low-amplitude momentary current glitches.
After an extended overcurrent condition, a fault is
detected and the MOSFET gate is discharged.Fast Comparator. This comparator has a fixed
response time and a higher 200mV threshold volt-
age. The fast comparator turns off the MOSFET
immediately after it detects a large amplitude event
such as a short circuit.
In each case, when a fault is encountered, the status
pin (STAT) goes low and the MAX4370 stays latched
off. Figure 3 shows the waveforms after a fault condi-
tion.
