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PDF MAX4370 Data sheet ( Hoja de datos )
| Número de pieza | MAX4370 | |
| Descripción | Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protection | |
| Fabricantes | Maxim Integrated | |
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19-1472; Rev 0; 4/99
Current-Regulating Hot-Swap Controller with
DualSpeed/BiLevel Fault Protection
General Description
The 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.
Applications
Hot Board Insertion
Solid-State Circuit Breaker
Features
o DualSpeed/BiLevel Protection During Normal
Operation
o Inrush Current Regulated at Start-Up
o Resides Either on the Backplane or on the
Removable Card
o Programmable Start-Up Period and Response
Time
o Allows Safe Board Insertion and Removal from
Live Backplane
o Protection for +3V to +12V Single Supplies
o Latched Off After Fault Condition
o Status Output Pin
o Internal Charge Pump Generates Gate Drive for
External N-Channel MOSFET
Ordering Information
PART
MAX4370ESA
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
8 SO
Pin Configuration appears at end of data sheet.
BACKPLANE REMOVABLE CARD
VCC
RSENSE
M1
N
STAT
GND
ON
VIN
STAT
VSEN
GATE
ON
CSPD
CSPD
MAX4370
GND
Typical Operating Circuit
VOUT
CBOARD
CTIM
CTIM
DualSpeed/BiLevel is a trademark of Maxim Integrated Products.
†Patent Pending
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
1 page  
Current-Regulating Hot-Swap Controller with
DualSpeed/BiLevel Fault Protection
Typical 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.)
GATE CHARGE CURRENT
vs. GATE VOLTAGE
120
VIN = 12V
100
GATE CHARGE CURRENT
vs. TEMPERATURE
150
125 VIN = 12V
VGATE = 0
GATE VOLTAGE vs. INPUT VOLTAGE
25
IGATE = 10µA
20 TA = +85°C
80
VIN = 3.0V
60
40
20
VIN = 5.0V
100
75 VIN = 5V
50
VIN = 3V
25
15 TA = +25°C
10 TA = -40°C
5
0
0
400
2 4 6 8 10 12 14 16 18 20
VGATE (V)
GATE DISCHARGE CURRENT
vs. GATE VOLTAGE
350
VIN = 3V
300
250
0
-40
-15 -10 35
60
TEMPERATURE (°C)
85
0
0 2 4 6 8 10 12 14
VIN (V)
GATE DISCHARGE CURRENT
vs. TEMPERATURE
400
350
VIN = 3V
300
250
START-UP TIME (CBOARD = 470µF)
MAX4370-15
ON
ILOAD
(1A/div)
VGATE
(2V/div)
200
150 VIN = 5V VIN = 12V
100
50 TRIGGERED BY A FAULT
OR BY ON FALLING
0
0 2 4 6 8 10 12 14 16 18 20
VGATE (V)
START-UP TIME (CBOARD = 0)
MAX4370-16
ON
200
150 VIN = 5V & 12V
100
VGATE = VIN
50 TRIGGERED BY A FAULT
OR BY ON FALLING
0
-40 -15 10 35 60
TEMPERATURE (°C)
85
START-UP TIME
(EXTERNAL CGATE = 22nF, CBOARD = 470µF)
MAX4370-17
ON
VOUT
(2V/div)
500µs/div
CBOARD = 470µF, RSENSE = 100mΩ,
CTIM = 10nF, CGATE = 0
TURN-OFF TIME (CBOARD = 470µF)
MAX4370-18
ON
VGATE
(2V/div)
ILOAD
(1A/div)
VGATE
(2V/div)
ILOAD
(1A/div)
0A
VOUT
(2V/div)
VOUT
(2V/div)
VOUT
(2V/div)
100µs/div
CBOARD = 0, RSENSE = 100mΩ,
CTIM = 10nF, CGATE = 0
1ms/div
CBOARD = 470µF, RSENSE = 100mΩ,
CGATE = 22nF, CTIM = 10nF, RS = 0
0V
50µs/div
CBOARD = 470µF, RSENSE = 100mΩ,
CGATE = 0
VGATE
(2V/div)
_______________________________________________________________________________________ 5
5 Page 
Current-Regulating Hot-Swap Controller with
DualSpeed/BiLevel Fault Protection
__________Applications Information
Component Selection
N-Channel MOSFET
Select the external N-channel MOSFET according to
the application’s current level. The MOSFET’s RDS(ON)
should be chosen low enough to have a minimum volt-
age drop at full load to limit the MOSFET power dissipa-
tion. High RDS(ON) can cause output ripple if the board
has pulsing loads, or it can trigger an external under-
voltage reset monitor at full load. Determine the
device’s power rating requirement to accommodate a
short-circuit condition on the board during start-up (see
MOSFET Thermal Considerations).
MOSFETs can typically withstand single-shot pulses
with higher dissipation than the specified package rat-
ing. Also, since part of the inrush current limiting is
achieved by limiting the gate dV/dt, it is not necessary
to use a MOSFET with low gate capacitance. Table 2
lists some recommended manufacturers and compo-
nents.
Sense Resistor
The slow comparator threshold voltage is set at 50mV.
Select a sense resistor that causes a 50mV voltage
drop at a current level above the maximum normal
operating current. Typically, set the overload current at
1.2 to 1.5 times the nominal load current. The fast com-
parator threshold is set at 200mV. This sets the fault
current limit at four times the overload current limit.
Choose the sense-resistor power rating to accommo-
date the overload current (Table 3):
PSENSE = (IOVERLOAD)2 · RSENSE
Start-Up Timing Capacitor (CTIM)
The start-up period (tSTART) is determined by the capaci-
tor connected at CTIM. This determines the maximum
time allowed to completely turn on the MOSFET.
The default value for tSTART is chosen by leaving CTIM
floating and is approximately 5.5µs. This is also the
minimum value (not controlled and dependent on stray
Table 2. Component Manufacturers
COMPONENT
Sense Resistors
MOSFETs
MANUFACTURER
Dale-Vishay
IRC
Fairchild
International Rectifier
Motorola
capacitance). Longer timings are determined by the
value of the capacitor, according to Figure 6, and can
be determined as follows:
tSTART (ms) = 0.31 · CTIM (nF)
Set the tSTART timer to allow the MOSFET to be
enhanced and the load capacitor to be completely
charged.
There are two methods of completing the start-up
sequences. Case A describes a start-up sequence that
does not use the current-limiting feature and slowly turns
on the MOSFET by limiting the gate dV/dt. Case B uses
the current-limiting feature and turns on the MOSFET as
fast as possible while still preventing high inrush current.
1000
100
10
1
0.1
0.01
0.001
0.01
0.1 1
10 100
CAPACITANCE (nF)
1000
Figure 6. Start-Up Period vs. CTIM
Table 3. Current Levels vs. RSENSE
RSENSE
(mΩ)
10
50
100
OVERLOAD
THRESHOLD SET BY
SLOW COMPARATOR
(A)
5
1
0.5
FAULT CURRENT
THRESHOLD SET BY
FAST COMPARATOR
(A)
20
4
2
PHONE
402-564-3131
704-264-8861
888-522-5372
310-322-3331
602-244-3576
INTERNET
www.vishay.com
www.irctt.co
www.fairchildsemi.com
www.irf.com
www.mot-sps.com/ppd/
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet MAX4370.PDF ] | |
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