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.
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
MAX4370
†
Ordering Information
PART
MAX4370ESA
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
8 SO
Pin Configuration appears at end of data sheet.
Applications
Hot Board Insertion
Solid-State Circuit Breaker
Typical Operating Circuit
BACKPLANE
V
CC
REMOVABLE CARD
R
SENSE
M1
N
V
OUT
C
BOARD
V
IN
STAT
GND
ON
C
SPD
STAT
VSEN
GATE
MAX4370
ON
CSPD
GND
CTIM
C
TIM
DualSpeed/BiLevel is a trademark of Maxim Integrated Products.
†
Pg
________________________________________________________________
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.
Current-Regulating Hot-Swap Controller with
DualSpeed/BiLevel Fault Protection
MAX4370
ABSOLUTE MAXIMUM RATINGS
V
IN
to GND...........................................................................+15V
STAT to GND ..........................................................-0.3V to +14V
GATE to GND ..............................................-0.3V to (V
IN
+ 8.5V)
ON to GND (Note 1) ................................................. -1V to +14V
CSPD to GND .............-0.3V to the lower of (V
IN
+ 0.3V) or +12V
VSEN, CTIM to GND ....................................-0.3V to (V
IN
+ 0.3V)
Current into ON...................................................................±2mA
Current into Any Other Pin................................................±50mA
Continuous Power Dissipation (T
A
= +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
Note 1:
ON can be pulled below ground. Limiting the current to 2mA ensures that this pin is never lower than about -0.8V.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress rating s only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
IN
= +2.7V to +13.2V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at V
IN
= +5V and T
A
= +25°C.) (Note 2)
PARAMETER
POWER SUPPLIES
Input Voltage Range
Supply Current
CURRENT CONTROL
Slow Comparator
Threshold
Slow Comparator Response
Time
Fast Comparator Threshold
Fast Comparator Response
Time
VSEN Input Bias Current
MOSFET DRIVER
Start-Up Period
(Note 3)
Gate Charge Current
Turn-Off Time
t
START
I
GATE
t
OFF
100nF on CTIM
CTIM = floating
V
GATE
= V
IN
(Note 4)
Time from current overload to V
GATE
< 0.1V,
C
GATE
= 1000pF to GND (triggered by the fast
comparator during normal operation)
During start-up (current regulation provided by
fast comparator)
During turn-off, triggered by a fault in normal
operation or ON falling edge
Measured with respect to V
IN
; voltage at which
internal clamp circuitry is triggered
I
GATE
= 8.5µA, measured above V
IN
V
IN
≥
5V
V
IN
≥
2.7V
5
2.7
0.1
75
21
31
5.5
100
60
41
ms
µs
µA
µs
V
SC,TH
t
CSPD
V
FC,TH
t
FCD
I
B,VSEN
V
IN
- V
SEN
CSPD = floating
100nF on CSPD to GND
V
IN
- VSEN
10mV overdrive, from overload condition to GATE
discharging
VSEN = V
IN
T
A
= +25°C
T
A
= T
MIN
to T
MAX
45
43.5
10
10
180
20
20
200
460
0.2
10
50
55
56
40
40
220
mV
µs
ms
mV
ns
µA
V
IN
I
Q
ON = V
IN
2.7
0.6
13.2
1
V
mA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
80
µA
225
6.7
550
7.5
V
V
V
Gate Discharge Current
I
GATE,DIS
Maximum Gate Voltage
Minimum Gate Drive Voltage
Gate Overvoltage Threshold
Start-up is initiated only if V
GATE
is less than this
voltage
2
_______________________________________________________________________________________
Current-Regulating Hot-Swap Controller with
DualSpeed/BiLevel Fault Protection
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= +2.7V to +13.2V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at V
IN
= +5V and T
A
= +25°C.) (Note 2)
PARAMETER
ON COMPARATOR
Threshold Voltage
Hysteresis
Power-Supply Rejection
Ratio
Propagation Delay
Input Voltage Range
Input Bias Current
ON Pulse Width Low
DIGITAL OUTPUT
(STAT)
Output Leakage Current
Output Voltage Low
V
OL
V
IN
UNDERVOLTAGE LOCKOUT
Threshold
Hysteresis
UVLO to Start-Up Delay
V
UVLO
V
UVLO,HYST
t
D,UVLO
Time which input voltage must exceed under-
voltage lockout before start-up is initiated
100
Start-up is initiated when this threshold is
reached at V
IN
2.25
100
150
200
2.67
V
mV
ms
V
STAT
≤
+13.2V
I
SINK
= 1mA
1
0.4
µA
V
V
TH,ON
V
HYST
PSRR
t
D,COMP
V
ON
I
B,ON
t
RESTART
To restart after a fault
20
2.7V
≤
V
IN
≤
13.2V
10mV overdrive
Input can be driven to the absolute maximum
limit without false output inversion
-0.1
0.001
V
IN
= 5V, rising threshold
0.575
0.6
3
0.1
10
13.2
1
1
0.625
V
mV
mV/V
µs
V
µA
µs
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX4370
3
Note 2:
All devices are 100% tested at T
A
= +25°C. All temperature limits are guaranteed by design.
Note 3:
The start-up period (t
START
) 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 V
GATE
(see Typical
Operating Characteristics.)
_______________________________________________________________________________________
Current-Regulating Hot-Swap Controller with
DualSpeed/BiLevel Fault Protection
MAX4370
Typical Operating Characteristics
(Circuit of Figure 7, V
IN
= 5V, R
SENSE
= 100mΩ, M1 = FDS6670A, C
BOARD
= 470µF, C
GATE
= 0, R
S
= 0, T
A
= +25°C, unless other-
wise noted.)
SLOW COMPARATOR THRESHOLD
vs. INPUT VOLTAGE
MAX4370 toc02
SUPPLY CURRENT vs. INPUT VOLTAGE
MAX4370 toc01
SUPPLY CURRENT vs. TEMPERATURE
1.0
0.9
0.8
SUPPLY CURRENT (mA)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
V
IN
= 3V
V
IN
= 12V
V
IN
= 5V
ON = V
IN
51.0
50.8
50.6
50.4
V
SC, TH
(mV)
50.2
50.0
49.8
49.6
49.4
49.2
49.0
-15
10
35
60
85
0
0.9
0.8
SUPPLY CURRENT (mA)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
2
4
6
8
10
12
ON = GND
ON = V
IN
I
GATE
= 10µA
T
A
= +25°C
T
A
= -40°C
T
A
= +85°C
14
0
-40
2
4
6
8
10
12
14
V
IN
(V)
TEMPERATURE (°C)
V
IN
(V)
SLOW COMPARATOR
RESPONSE TIME vs. INPUT VOLTAGE
24
23
22
t
CSPD
(µs)
21
20
19
18
MAX4370 toc05
FAST COMPARATOR THRESHOLD
vs. INPUT VOLTAGE
MAX4370 toc06
FAST COMPARATOR RESPONSE TIME
vs. OVERDRIVE VOLTAGE
MAX4370 toc07
24
23
22
21
20
19
18
210
108
700
600
500
t
FCD
(ns)
400
V
IN
= 5V
300
200
100
V
IN
= 3V
V
IN
= 12V
CSPD = 110nF
TIME IN ms
206
204
t
CSPD
(ms)
V
FC, TH
(mV)
202
200
198
196
194
192
190
T
A
= +85°C
T
A
= -40°C
T
A
= +25°C
CSPD = 0
TIME IN
µs
0
2
4
6
8
10
12
14
0
2
4
V
IN
(V)
6
8
V
IN
(V)
10
12
14
0
1
10
V
OD
(mV)
100
1000
FAST COMPARATOR RESPONSE TIME
vs. TEMPERATURE
490
480
470
t
FCD
(ns)
460
450
440
430
420
410
400
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
V
OD
= 10mV
250
0
2
V
IN
= 3V
V
IN
= 12V
310
V
IN
= 5V
MAX4370 toc08
START-UP TIME
vs. INPUT VOLTAGE
350
C
TIM
= 100nF
TIME IN ms
MAX4370 toc09
500
35
330
33
t
START
(ms)
t
START
(µs)
31
C
TIM
= 1nF
TIME IN
µs
290
29
270
27
25
4
6
8
10
12
14
V
IN
(V)
4
_______________________________________________________________________________________
MAX4370 toc03
1.0
Current-Regulating Hot-Swap Controller with
DualSpeed/BiLevel Fault Protection
Typical Operating Characteristics (continued)
(Circuit of Figure 7, V
IN
= 5V, R
SENSE
= 100mΩ, M1 = FDS6670A, C
BOARD
= 470µF, C
GATE
= 0, R
S
= 0, T
A
= +25°C, unless other-
wise noted.)
GATE CHARGE CURRENT
vs. GATE VOLTAGE
MAX4370 toc10
MAX4370
GATE CHARGE CURRENT
vs. TEMPERATURE
V
GATE
= 0
125
100
I
GATE
(µA)
V
IN
= 12V
MAX4370 toc11
GATE VOLTAGE vs. INPUT VOLTAGE
I
GATE
= 10µA
20
T
A
= +85°C
T
A
= +25°C
MAX4370 toc12
120
100
80
I
GATE
(µA)
V
IN
= 3.0V
60
40
20
0
0
2
4
6
8
150
25
V
IN
= 12V
V
IN
= 5.0V
75
50
V
IN
= 5V
V
GATE
(V)
15
10
V
IN
= 3V
25
0
5
T
A
= -40°C
0
-40
-15
-10
35
60
85
0
2
4
6
8
10
12
14
TEMPERATURE (°C)
V
IN
(V)
10 12 14 16 18 20
V
GATE
(V)
GATE DISCHARGE CURRENT
vs. GATE VOLTAGE
MAX4370 toc13
GATE DISCHARGE CURRENT
vs. TEMPERATURE
MAX4370 toc14
START-UP TIME (C
BOARD
= 470µF)
MAX4370-15
400
350
300
I
GATE
(µA)
V
IN
= 3V
400
350
V
IN
= 3V
300
I
GATE
(µA)
250
200
150
100
V
IN
= 5V & 12V
V
GATE
= V
IN
TRIGGERED BY A FAULT
OR BY ON FALLING
-40
-15
10
35
60
ON
V
GATE
(2V/div)
250
200
150
100
50
0
0
2
4
6
8
10 12 14 16 18 20
V
GATE
(V)
TRIGGERED BY A FAULT
OR BY ON FALLING
V
IN
= 5V
V
IN
= 12V
I
LOAD
(1A/div)
V
OUT
(2V/div)
50
0
85
TEMPERATURE (°C)
500µs/div
C
BOARD
= 470µF, R
SENSE
= 100mΩ,
C
TIM
= 10nF, C
GATE
= 0
START-UP TIME (C
BOARD
= 0)
MAX4370-16
START-UP TIME
(EXTERNAL C
GATE
= 22nF, C
BOARD
= 470µF)
MAX4370-17
TURN-OFF TIME (C
BOARD
= 470µF)
MAX4370-18
ON
V
GATE
(2V/div)
ON
V
GATE
(2V/div)
ON
I
LOAD
(1A/div)
I
LOAD
(1A/div)
0A
V
OUT
(2V/div)
V
OUT
(2V/div)
V
OUT
(2V/div)
0V
V
GATE
(2V/div)
50µs/div
C
BOARD
= 470µF, R
SENSE
= 100mΩ,
C
GATE
= 0
100µs/div
C
BOARD
= 0, R
SENSE
= 100mΩ,
C
TIM
= 10nF, C
GATE
= 0
1ms/div
C
BOARD
= 470µF, R
SENSE
= 100mΩ,
C
GATE
= 22nF, C
TIM
= 10nF, R
S
= 0
_______________________________________________________________________________________
5
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