MAX6397VATA+ [MAXIM]
Power Supply Support Circuit, Adjustable, 1 Channel, BICMOS, 3 X 3 MM, 0.80 MM HEIGHT, ROHS COMPLIANTMO-229WEEC, TDFN-8;
| 型号： | MAX6397VATA+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Power Supply Support Circuit, Adjustable, 1 Channel, BICMOS, 3 X 3 MM, 0.80 MM HEIGHT, ROHS COMPLIANTMO-229WEEC, TDFN-8 信息通信管理 |
| 文件： | 总18页 (文件大小：1942K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
EVALUATION KIT AVAILABLE
MAX6397/MAX6398
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
General Description
Features
● 5.5V to 72V Wide Supply Voltage Range
The MAX6397/MAX6398 are small, high-voltage over-
voltage protection circuits. These devices disconnect
the output load or limit the output voltage during an
input overvoltage condition. These devices are ideal for
applications that must survive high-voltage transients
such as those found in industrial applications.
● Overvoltage Protection Controllers Allow User to Size
External n-Channel MOSFETs
● Internal Charge-Pump Circuit Ensures MOSFET
Gate-to-Source Enhancement for Low R
Performance
DS(ON)
The MAX6397/MAX6398 monitor the input or output
voltages and control an external n-channel MOSFET to
isolate or limit the load from overvoltage transient energy.
When the monitored input voltage is below the user-
adjustable overvoltage threshold, the external n-channel
MOSFET is turned on by the GATE output. In this mode,
the internal charge pump fully enhances the n-channel
MOSFET with a 10V gate-to-source voltage.
● Disconnect or Limit Output from Input During
Overvoltage Conditions
● Adjustable Overvoltage Threshold
● Thermal-Shutdown Protection
● Always-On, Low-Current (37µA) Linear Regulator
Sources Up to 100mA (MAX6397)
● Fully Specified from -40°C to +125°C (T )
J
When the input voltage exceeds the overvoltage threshold,
the protection can disconnect the load from the input by
quickly forcing the GATE output low. In some applications,
disconnecting the output from the load is not desirable. In
these cases, the protection circuit can be configured to
act as a voltage limiter where the GATE output sawtooths
to limit the voltage to the load.
● Small, Thermally Enhanced 3mm x 3mm TDFN Package
Ordering Information
PART
TEMP RANGE
-40°C to +125°C
-40°C to +125°C
PIN-PACKAGE
8 TDFN-EP**
6 TDFN-EP**
MAX6397_ATA-T*
MAX6398ATT-T*
The MAX6397 also offers an always-on linear regulator
that is capable of delivering up to 100mA of output current.
This high-voltage linear regulator consumes only 37µA of
quiescent current.
*Replace “-T” with “+T” for lead(Pb)-free/RoHS-compliant packages.
**EP = Exposed pad.
The MAX6397 linear regulator is offered in four output
voltage options and a choice of a 92.5% or 87.5% POK
threshold assertions. See the Selector Guide.
The regulator is offered with output options of 5V, 3.3V,
2.5V, or 1.8V. An open-drain, power-good output (POK)
asserts when the regulator output falls below 92.5% or
87.5% of its nominal voltage.
Selector Guide and Typical Operating Circuit appear at end
of data sheet.
Pin Configurations
The MAX6397/MAX6398 include internal thermal-
shutdown protection, disabling the external MOSFET
and linear regulator if the chip reaches overtemperature
conditions. The devices operate over a wide 5.5V to
72V supply voltage range, are available in small TDFN
packages, and are fully specified from -40°C to +125°C.
REG OUT GATE GND
TOP VIEW
8
7
6
5
*EP
MAX6397
Applications
● Industrial
®
● FireWire
1
2
3
4
● Notebook Computers
● Wall Cube Power Devices
IN SHDN SET POK
TDFN
*EXPOSED PAD. CONNECT TO GND.
Pin Configurations continued at end of data sheet.
FireWire is a registered trademark of Apple Computer, Inc.
19-3668; Rev 6; 7/14
MAX6397/MAX6398
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
Absolute Maximum Ratings
(All pins referenced to GND, unless otherwise noted.)
Continuous Power Dissipation (T = +70°C)
A
IN, GATE, OUT......................................................-0.3V to +80V
6-Pin TDFN (derate 18.2mW/°C above +70°C) ........1455mW
8-Pin TDFN (derate 18.2mW/°C above +70°C) ........1455mW
SHDN .........................................................-0.3V to (V + 0.3V)
IN
GATE to OUT .......................................................... -0.3 to +20V
SET, REG, POK ....................................................-0.3V to +12V
Maximum Current:
Operating Temperature Range (T )................. -40°C to +125°C
A
Junction Temperature......................................................+150°C
Storage Temperature Range............................ -65°C to +150°C
Lead Temperature ...........................................................+300°C
IN, REG ........................................................................350mA
All Remaining Pins.............................................................50mA
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.
Electrical Characteristics
(V = 14V; C
= 6000pF, C
= 4.7µF, T = T = -40°C to +125°C, unless otherwise noted. Typical values are at T = T = +25°C.)
IN
GATE
REG
A
J
A
J
(Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
72
UNITS
Supply Voltage Range
V
5.5
V
IN
SHDN = high, no load (MAX6397)
SHDN = high, (MAX6398)
118
104
37
11
140
130
45
Input Supply Current
µA
SHDN = low, no load (MAX6397)
SHDN = low, (MAX6398)
20
IN Undervoltage Lockout
V
rising, enables GATE
4.66
5
5.50
V
IN
IN Undervoltage-Lockout
Hysteresis
V
falling, disables GATE
175
mV
IN
SET Threshold Voltage
SET Threshold Hysteresis
SET Input Current
V
With respect to GND
1.181
-50
1.215
4
1.248
+50
V
TH
V
%
HYST
I
nA
µs
SET
Startup Response Time
t
SHDN rising (Note 2)
100
1
START
GATE rising from GND to V
+ 8V,
OUT
GATE Rise Time
ms
µs
C
= 6000pF, OUT = GND
GATE
SET-to-GATE Propagation
Delay
t
SET rising from V - 100mV to V + 100mV
0.75
OV
TH
TH
V
3.8V
+
V
4.2V
+
V
4.6V
+
IN
IN
IN
V
V
= V = 6V, R to IN = 1MΩ
GATE
OUT
IN
GATE Output High Voltage
V
V
OH
V
+
V
+
V
+
IN
IN
IN
= V ; V ≥ 14V, R
to IN = 1MΩ
OUT
IN IN
GATE
8.5V
9.2V
11.5V
GATE Output Low Voltage
GATE Charge-Pump Current
GATE-to-OUT Clamp Voltage
V
GATE sinking 20mA, V
= GND
OUT
0.38
18
V
µA
V
OL
I
GATE = GND
75
1
GATE
V
13
CLMP
SHDN Logic-High Input Voltage
SHDN Logic-Low Input Voltage
V
1.4
IH
V
0.4
48
IL
V
= 2V, SHDN is internally pulled
SHDN
SHDN Input Pulldown Current
µA
down to GND
Thermal Shutdown (Note 3)
Thermal-Shutdown Hysteresis
REGULATOR (MAX6397)
+150
20
°C
°C
I
I
= 1mA
40
60
REG
REG
Ground Current
I
SHDN = GND
µA
GND
= 100mA
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MAX6397/MAX6398
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
Electrical Characteristics (continued)
(V = 14V; C
= 6000pF, C
= 4.7µF, T = T = -40°C to +125°C, unless otherwise noted. Typical values are at T = T = +25°C.)
IN
GATE
REG
A
J
A
J
(Note 1)
PARAMETER
SYMBOL
CONDITIONS
= 1mA
MIN
4.925
4.85
TYP
MAX
5.120
5.15
3.36
3. 36
2.542
2.55
1.837
1.837
0.12
1.2
UNITS
I
5
REG
MAX6397L/M
MAX6397S/T
MAX6397Y/Z
MAX6397V/W
1mA < I
< 100mA
< 100mA
< 100mA
< 100mA
REG
I
= 1mA
3.243
3.201
2.246
2.41
3.3
2.5
1.8
REG
V
1mA < I
REG Output Voltage
REG
V
REG
(V ≥ V
+ 1.8V)
IN
REG
I
= 1mA
REG
1mA < I
REG
I
= 1mA
1.76
REG
1mA < I
1.715
REG
mV/V
5.5V ≤ V ≤ 72V, I
= 1mA, V
= 5V
IN
REG
REG
Dropout Voltage (Note 4)
Current Limit
∆V
DO
5.5V ≤ V ≤ 72V, I
= 100mA, V
= 5V
IN
REG
REG
V
= 14V
150
300
mA
IN
Overvoltage-Protection
Threshold
% of
V
105
15
OVP
V
REG
Overvoltage-Protection Sink
Current
I
V
= 1.1 x V
(Nominal)
REG
mA
OVP
REG
6.5V ≤ V ≤ 72V, I
= 10mA, V = 5V
REG
0.22
0.05
IN
REG
REG
REG
∆V
∆V
/
REG
Line Regulation (Note 5)
5.5V ≤ V ≤ 72V, I
= 1mA, V
= 5V
mV/mA
IN
REG
REG
5.5V ≤ V ≤ 72V, I
= 100mA, V
= 5V
1.5
IN
REG
∆VREG /
∆IREG
Load Regulation
1mA ≤ I
≤ 100mA, V
= 5V
REG
0.8
mV/mA
REG
Power-Supply Rejection Ratio
Startup Response Time
I
= 10mA, f = 100Hz, 0.5V
55
dB
µs
REG
P-P
t
R
L
= 500Ω, V
= 5V, C
= 4.7µF
180
START
REG
REG
REG
4.500
4.230
2.966
2.805
2.250
2.125
1.590
1.524
4.67
4.780
4.500
3.140
2.970
2.375
2.250
1.696
1.625
M
T
4.375
3.053
2.892
2.304
2.188
1.653
1.575
35
S
Z
POK Assertion Threshold
(MAX6397 Only)
V
V
POK_TH
Y
W
V
REG-to-POK Delay
V
V
V
rising or falling
= 5V
µs
nA
V
REG
POK
POK Leakage Current
POK Output Low Voltage
100
0.3
V
≥ 1.5V, I
= 1.6mA, POK asserted
OL
IN
SINK
Note 1: Specifications to T = -40°C are guaranteed by design and not production tested.
A
Note 2: The MAX6397/MAX6398 power up with the external FET in off mode (V
= GND). The external FET turns on t
GATE
START
after the device is powered up and all input conditions are valid.
Note 3: For accurate overtemperature-shutdown performance, place the device in close thermal contact with the external MOSFET.
Note 4: Dropout voltage is defined as V - V
Note 5: Operations beyond the thermal dissipation limit may permanently damage the device.
when V
is 2% below the value of V
for V = V
(nominal) + 2V.
Maxim Integrated
IN
REG
REG
REG
IN
REG
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MAX6397/MAX6398
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
Typical Operating Characteristics
(V = 14V, C
IN
= 4.7μF, I
= 0, unless otherwise noted.)
REG
REG
SUPPLY CURRENT
vs. INPUT VOLTAGE
SUPPLY CURRENT
vs. INPUT VOLTAGE
SUPPLY CURRENT vs. TEMPERATURE
180
170
160
150
140
130
120
110
100
90
160
120
110
100
90
MAX6397
MAX6397
GATE ON
MAX6398
GATE ON
140
120
100
80
V
IN
= 72V
80
70
V
IN
= 14V
60
60
50
40
80
40
0
10 20 30 40 50 60 70 80
INPUT VOLTAGE (V)
-50 -25
0
25
50
75 100 125
0
20
40
60
80
TEMPERATURE (°C)
INPUT VOLTAGE (V)
SUPPLY CURRENT
vs. TEMPERATURE
SHUTDOWN SUPPLY CURRENT
vs. INPUT VOLTAGE (MAX6397)
SHUTDOWN SUPPLY CURRENT
vs. INPUT VOLTAGE
20
18
16
14
12
10
8
140
130
120
110
100
90
50
45
40
35
30
25
20
MAX6398
GATE OFF
MAX6398
GATE ON
REGULATOR ON
GATE OFF
V
IN
= 72V
V
IN
= 14V
6
4
2
80
0
50
10 20 30 40
INPUT VOLTAGE (V)
-50 -25
0
25
50
75 100 125
0
60 70 80
0
20
40
60
80
TEMPERATURE (°C)
INPUT VOLTAGE (V)
GATE-DRIVE VOLTAGE
vs. INPUT VOLTAGE
UVLO THRESHOLD
vs. TEMPERATURE
SET THRESHOLD vs. TEMPERATURE
1.240
1.236
1.232
1.228
1.224
1.220
1.216
1.212
1.208
1.204
1.200
12
10
8
6.0
5.8
5.6
5.4
5.2
5.0
4.8
4.6
4.4
4.2
4.0
V
OUT
= V
IN
6
4
2
0
4
6
8
10 12 14 16 18 20 22 24
INPUT VOLTAGE (V)
-50 -25
0
25
50
75 100 125
-50 -25
0
25
50
75 100 125
TEMPERATURE (°C)
TEMPERATURE (°C)
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MAX6397/MAX6398
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
Typical Operating Characteristics (continued)
(V = 14V, C
= 4.7μF, I
= 0, unless otherwise noted.)
IN
REG
REG
DROPOUT VOLTAGE
vs. REG LOAD CURRENT
REG OUTPUT VOLTAGE
vs. LOAD CURRENT AND TEMPERATURE
GATE-TO-OUT CLAMP VOLTAGE
vs. TEMPERATURE
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
5.20
5.15
5.10
5.05
5.00
4.95
4.90
17.0
16.9
16.8
16.7
16.6
16.5
16.4
16.3
16.2
16.1
16.0
MAX6397L
MAX6397L
T
= +125°C
A
I
= 10mA
LOAD
I
= 50mA
LOAD
T
A
= +25°C
I
= 100mA
LOAD
T
A
= -40°C
-50 -25
0
25
50
75 100 125
0
20 40 60 80 100 120 140 160 180
REG LOAD CURRENT (mA)
-40 -25 -10
5
20 35 50 65 80 95 110 125
TEMPERATURE (°C)
TEMPERATURE (°C)
MAXIMUM REG OUTPUT VOLTAGE
vs. LOAD CURRENT AND TEMPERATURE
GATE-DRIVE VOLTAGE
vs. TEMPERATURE
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
10.500
10.495
10.490
10.485
10.480
10.475
10.470
10.465
10.460
10.455
10.450
0
5.2
5.0
4.8
4.6
4.4
4.2
4.0
C = 10µF
REG
T
= -40°C
A
I
= 10mA
REG
-10
-20
-30
-40
-50
-60
-70
T
= +25°C
A
T
A
= +125°C
THERMAL
SHUTDOWN
0
40 80 120 160 200 240 280 320 360 400
LOAD CURRENT (mA)
-50 -25
0
25
50
75 100 125
10
100
1k
10k 100k
1M
10M
TEMPERATURE (°C)
FREQUENCY (Hz)
STARTUP WAVEFORM
STARTUP WAVEFORM FROM SHUTDOWN
(R
LOAD
= 100Ω, C = 10µF, C
= 10µF)
OUT
MAX6397 toc16
(C = 10µF, C
IN
= 10µF)
IN
OUT
MAX6397 toc17
R
LOAD
= 100Ω
V
IN
V
SHDN
10V/div
2V/div
V
GATE
V
GATE
10V/div
10V/div
V
OUT
V
OUT
10V/div
10V/div
I
I
OUT
OUT
200mA/div
200mA/div
400µs/div
4ms/div
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MAX6397/MAX6398
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
Typical Operating Characteristics (continued)
(V = 14V, C
= 4.7μF, I
= 0, unless otherwise noted.)
IN
REG
REG
OVERVOLTAGE SWITCH FAULT
VOLTAGE LIMIT FAULT
MAX6397 toc18
MAX6397 toc19
V
OV
= 30V
V
= 30V
V
IN
V
IN
OV
20V/div
20V/div
V
GATE
V
GATE
20V/div
20V/div
V
OUT
V
OUT
20V/div
20V/div
V
V
REG
REG
5V/div
5V/div
200µs/div
1ms/div
TRANSIENT RESPONSE
REG LOAD-TRANSIENT RESPONSE
MAX6397 toc21
MAX6397 toc20
C
= 10µF
= 10mA
REG
C
REG
= 10µF
I
REG
V
REG
V
IN
AC-COUPLED
500mV/div
10V/div
I
REG
V
REG
100mA/div
100mV/div
400µs/div
1ms/div
REGULATOR STARTUP WAVEFORM
REGULATOR POK ASSERTION
MAX6397 toc23
MAX6397 toc22
I
= 10mA
REG
V
REG
V
IN
2V/div
10V/div
0V
V
REG
2V/div
V
POK
2V/div
0V
0A
V
POK
I
2V/div
REG
200mA/div
I
= 0
REG
1ms/div
100µs/div
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MAX6397/MAX6398
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
Pin Description
PIN
NAME
FUNCTION
MAX6397
MAX6398
1
1
IN
Supply Voltage Input. Bypass with a minimum 10µF capacitor to GND.
Shutdown Input. Drive SHDN low to force GATE low, turning off the external n-channel
MOSFET. REG remains active when in shutdown mode. SHDN is internally pulled down
to GND with a 1µA source. Connect to IN for normal operation.
2
3
2
3
SHDN
Overvoltage-Threshold-Adjustment Input. Connect SET to an external resistor voltage-
divider network to OUT (overvoltage limiter) or IN (overvoltage switch) to adjust the
desired overvoltage-limit threshold. Use SET to monitor a system input or output voltage.
SET
Open-Drain Output. POK remains low until REG exceeds 92.5% or 87.5% of REG
nominal output voltage. Connect to an external pullup resistor.
4
5
—
4
POK
GND
Ground
Gate-Drive Output. Connect GATE to the gate of an external n-channel MOSFET.
GATE is a charge pump with a 75µA pullup current to 10V (typ) above IN during normal
operation. GATE is quickly shorted to OUT during an overvoltage condition. GATE pulls
low when SHDN is low.
6
5
GATE
7
8
6
OUT
REG
EP
Output-Voltage-Sense Input. Connect to the source of the external n-channel MOSFET.
Regulator Output. Fixed 5.0V, 3.3V, 2.5V, or 1.8V output. REG sources up to 100mA.
Bypass with a minimum 4.7µF capacitor to GND.
—
—
—
Exposed Pad. Connect to ground plane.
disconnecting the load from the power source, and then
slowly enhances upon removal of the overvoltage
Detailed Description
The MAX6397/MAX6398 are ultra-small, low-current,
high-voltage protection circuits for applications that must
survive high-voltage transient conditions. These devices
monitor the input/output voltages and control an external
n-channel MOSFET to isolate the load or to regulate the
output voltage from overvoltage-transient energy. The
controller allows system designers to size the external
MOSFET to their load current and board size.
condition. In overvoltage-limit mode, the output volt-
age is monitored and the MAX6397/MAX6398 regulate
the source of the external MOSFET at the adjusted
overvoltage threshold, allowing devices within the system
to continue operating during an overvoltage condition.
The MAX6397/MAX6398 undervoltage lockout (UVLO)
function disables the devices as long as the input remains
below the 5V (typ) UVLO turn-on threshold. The MAX6397/
MAX6398 have an active-lows SHDN input to turn off the
external MOSFET, disconnecting the load and reducing
power consumption. After power is applied and SHDN is
driven above its logic-high voltage, there is a 100µs delay
before GATE enhancement commences.
The MAX6397/MAX6398 drive the MOSFET’s gate high
when the monitored input voltage is below the adjustable
overvoltage threshold. An internal charge-pump circuit
provides a 5V to 10V gate-to-source drive (see the Typical
Operating Characteristics) to ensure low input-to-load
voltage drops in normal operating modes. When the input
voltage rises above the user-adjusted overvoltage thresh-
old, GATE pulls to OUT, turning off the MOSFET.
The MAX6397 integrates a high input voltage, low-
quiescent-current linear regulator, in addition to an
overvoltage-protector circuit. The linear regulator remains
enabled at all times to power low-current “always-on”
applications (independent of the state of the external
MOSFET). The regulator is offered with several standard
output voltage options (5V, 3.3V, 2.5V, or 1.8V). An open-
drain power-good output notifies the system if the regulator
The MAX6397/MAX6398 are configurable to operate
as overvoltage-protection switches or as closed-looped
voltage limiters. In overvoltage-protection switch
mode, the input voltage is monitored. When an
overvoltage condition occurs at IN, GATE pulls low,
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MAX6397/MAX6398
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
Power-OK Output
IN
POK is an open-drain output that goes low when REG
falls to 92.5% or 87.5% (see the Selector Guide) of its
nominal output voltage. To obtain a logic-level output,
connect a pullup resistor from POK to REG or another
system voltage. Use a resistor in the 100kΩ range to
minimize current consumption. POK provides a valid
THERMAL
PROTECTION
UVLO
logic-output level down to V = 1.5V.
IN
10V
CHARGE
PUMP
GATE Voltage
The MAX6397/MAX6398 use a high-efficiency charge
5V
pump to generate the GATE voltage. Upon V exceed-
ing the 5V (typ) UVLO threshold, GATE enhances 10V
IN
GATE
SET
above IN (for V ≥14V) with a 75µA pullup current. An
IN
OUT
overvoltage condition occurs when the voltage at SET
pulls above its 1.215V threshold. When the threshold is
crossed, GATE falls to OUT within 100ns with a 100mA
(typ) pulldown current. The MAX6397/MAX6398 include
an internal clamp to OUT that ensures GATE is limited to
18V (max) above OUT to prevent gate-to-source damage
to the external FET.
1.23V
SHDN
REG
LINEAR
REGULATOR
The GATE cycle during overvoltage-limit and overvoltage-
switch modes are quite similar but have distinct charac-
teristics. In overvoltage-switch mode (Figure 2a), GATE
MAX6397
MAX6398
POK
GND
is enhanced to V + 10V while the monitored IN volt-
IN
age remains below the overvoltage-fault threshold (SET
< 1.215V). When an overvoltage fault occurs (SET ≥
1.215V), GATE is pulled one diode below OUT, turning
off the external FET and disconnecting the load from the
V
POK_TH
MAX6397 ONLY
input. GATE remains low (FET off) as long as V is above
IN
the overvoltage-fault threshold. As V falls back below
the overvoltage-fault threshold (-5% hysteresis), GATE is
IN
Figure 1. Functional Diagram
again enhanced to V + 10V.
IN
output falls to 92.5% or 87.5% of its nominal voltage. The
MAX6397’s REG output operates independently of the
SHDN logic input.
The MAX6397/MAX6398 include internal thermal-
shutdown protection, disabling the external MOSFET and
linear regulator if the chip reaches overtemperature condi-
tions.
V
IN
10V/div
Linear Regulator (MAX6397 Only)
V
GATE
The MAX6397 is available with 5.0V, 3.3V, 2.5V, and 1.8V
factory-set output voltages. Each regulator sources up to
100mA and includes a current limit of 230mA. The linear
regulator operates in an always-on condition regardless
10V/div
V
OUT
10V/div
of the SHDN logic. For fully specified operation, V must
IN
10ms/div
be greater than 6.5V for the MAX6397L/M (5V regulator
output). The actual output current may be limited by the
operating condition and package power dissipation.
Figure 2a. MAX6397/MAX6398 GATE Waveform During
Overvoltage Switch Mode
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MAX6397/MAX6398
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
V
IN
10V/div
GATE
V
GATE
V
BATT
IN
OUT
10V/div
MAX6397
MAX6398
R1
R2
SET
V
OUT
10V/div
GND
4ms/div
Figure 2b. MAX6397/MAX6398 GATE Waveform During
Overvoltage Limit Mode
Figure 3. Overvoltage Switch Protection Configuration
In overvoltage-limit mode (Figure 2b), GATE is enhanced
MAX6398 slowly enhance GATE above OUT, reconnecting
the load to the power source.
to V + 10V. While the monitored OUT voltage remains
IN
below the overvoltage fault threshold (SET < 1.215V).
When an overvoltage fault occurs (SET ≥ 1.215V), GATE
is pulled low one diode drop below OUT until OUT drops
5% below the overvoltage-fault threshold. GATE is then
turned back on until OUT again reaches the overvoltage-
fault threshold and GATE is again turned off.
Overvoltage Limiter
When operating in overvoltage-limiter mode, the
MAX6397/MAX6398 feedback path (Figure 4) consists of
OUT, SET’s internal comparator, the internal gate charge
pump and the external n-channel MOSFET, which results
in the external MOSFET operating as a voltage regulator.
GATE cycles on-off-on-off-on in a sawtooth waveform until
OUT remains below the overvoltage-fault threshold and
During normal operation, GATE is enhanced 10V above
OUT. The external MOSFET source voltage is monitored
through a resistor-divider between OUT and SET. When
OUT rises above the adjusted overvoltage threshold,
an internal comparator sinks the charge-pump current,
discharging the external GATE, regulating OUT at the
set overvoltage threshold. OUT remains active during
GATE remains constantly on (V + 10V). The overvoltage
IN
limiter’s sawtooth GATE output operates the MOSFET in
a switched-linear mode while the input voltage remains
above the overvoltage-fault threshold. The sawtooth
frequency depends on the load capacitance, load current,
and MOSFET turn-on time (GATE charge current and
GATE capacitance).
GATE goes high when the following startup conditions are
met: V is above the UVLO threshold, SHDN is high, an
C
OUT
IN
overvoltage fault is not present and the device is not in
thermal shutdown.
GATE
V
BATT
IN
OUT
SET
Overvoltage Monitoring
MAX6397
MAX6398
R1
R2
When operating in overvoltage mode, the MAX6397/
MAX6398 feedback path (Figure 3) consists of IN, SET’s
internal comparator, the internal gate charge pump, and
the external n-channel MOSFET resulting in a switch-on/
off function. When the programmed overvoltage threshold
is tripped, the internal fast comparator turns off the external
GND
MOSFET, pulling GATE to OUT within t
and disconnect-
OV
ing the power source from the load. When IN decreases
below the adjusted overvoltage threshold, the MAX6397/
Figure 4. Overvoltage Limiter Protection Switch Configuration
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MAX6397/MAX6398
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
GATE
GATE
IN
IN
IN
OUT
IN
OUT
MAX6397
MAX6398
MAX6397
MAX6398
R1
R2
R1
R2
SET
SET
GND
GND
Figure 5. Setting the MAX6397/MAX6398 Overvoltage Threshold
the overvoltage transients and the MOSFET continues
to conduct during the overvoltage event, operating in
switched-linear mode.
Begin by selecting the total end-to-end resistance,
= R1 + R2. Choose R to yield a total
R
TOTAL
TOTAL
current equivalent to a minimum 100 x I
(SET’s input
SET
bias current) at the desired overvoltage threshold.
As the transient begins decreasing, OUT fall time will
depend on the MOSFET’s GATE charge, the internal
charge-pump current, the output load, and the tank
capacitor at OUT.
For example:
With an overvoltage threshold set to 20V:
R
< 20V/(100 x I
)
TOTAL
SET
For fast-rising transients and very large-sized MOSFETs,
add an additional external bypass capacitor from GATE to
GND to reduce the effect of the fast-rising voltages at IN.
The external capacitor acts as a voltage-divider working
against the MOSFETs’ drain-to-gate capacitance. For a
where I
is SET’s 50nA input bias current.
SET
R
< 4MΩ
TOTAL
Use the following formula to calcue R2:
R
6000pF C , a 0.1µF capacitor at GATE will reduce the
impact of the fast-rising V input.
IN
TOTAL
gd
R2 = V
×
TH
V
OV
Caution must be exercised when operating the MAX6397/
MAX6398 in voltage-limiting mode for long durations.
where V is the 1.215V SET rising threshold and V
TH
the overvoltage threshold.
is
OV
If the V is a DC voltage greater than the MOSFET’s
IN
maximum gate voltage, the FET will dissipate power
continuously. To prevent damage to the external MOSFET,
proper heatsinking should be implemented.
R2 = 243kΩ, use a 240kΩ standard resistor.
R
= R2 + R1, where R1 = 3.76MΩ.
TOTAL
Use a 3.79MΩ standard resistor.
Applications Information
A lower value for total resistance dissipates more power
but provides slightly better accuracy.
Setting Overvoltage Thresholds
SET provides an accurate means to set the overvoltage
level for the MAX6397/MAX6398. Use a resistor-divider
to set the desired overvoltage condition (Figure 5). SET
has a rising 1.215V threshold with a 5% falling hysteresis.
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MAX6397/MAX6398
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
Q1
IN
IN
GATE
GATE
V
BATT
V
BATT
LOAD
LOAD
MAX6397
MAX6398
MAX6397
MAX6398
OUT
OUT
GND
GND
(a)
(b)
Figure 6. Reverse-Battery Protection Using a Diode or p-Channel MOSFET
voltage. When the source voltage exceeds Q1’s threshold
Reverse-Battery Protection
voltage, Q1 turns on. Once the FET is on, the battery is
fully connected to the system and can deliver power to the
device and the load.
Use a diode or p-channel MOSFET to protect the
MAX6397/MAX6398 during a reverse-battery insertion
(Figures 6a, 6b). Low p-channel MOSFET on-resistance
of 30mΩ or less yields a forward-voltage drop of only a
few millivolts (versus hundreds of millivolts for a diode,
Figure 6a) thus improving efficiency.
An incorrectly inserted battery reverse-biases the FET’s
body diode. The gate remains at the ground potential.
The FET remains off and disconnects the reversed
battery from the system. The zener diode and resistor
combination prevent damage to the p-channel MOSFET
during an overvoltage condition.
Connecting a positive battery voltage to the drain of Q1
(Figure 6b) produces forward bias in its body diode, which
clamps the source voltage one diode drop below the drain
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MAX6397/MAX6398
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
V
BATT
1kΩ
IN
GATE
C
GATE
C
OUT
V
BATT
IN
LOAD
MAX6397
MAX6398
LOAD
GATE
60V
TVS
MAX6397
MAX6398
OUT
GND
OUT
GND
Figure 7. MAX6397/MAX6398 Controlling GATE Inrush Current
Figure 8. Protecting the MAX6397/MAX6398 Input from High-
Voltage Transients
Input Transients Clamping
REG Capacitor Selection for Stability
When the external MOSFET is turned off during an
overvoltage occurrence, stray inductance in the power
path may cause voltage ringing exceeding the MAX6397/
MAX6398 absolute maximum input (IN) supply rating.
The following techniques are recommended to reduce the
effect of transients:
For stable operation over the full temperature range
and with load currents up to 100mA, use ceramic
capacitor values greater than 4.7µF. Large output
capacitors help reduce noise, improve load-transient
response, and power-supply rejection at REG. Note that
some ceramic dielectrics exhibit large capacitance and
ESR variation with temperature. At lower temperatures, it
may be necessary to increase capacitance.
•
Minimize stray inductance in the power path using
wide traces, and minimize loop area including the
power traces and the return ground path.
Under normal conditions, use a 10µF capacitor at IN.
Larger input capacitor values and lower ESR provide
better supply-noise rejection and line-transient response.
•
Add a zener diode or transient voltage suppressor
(TVS) rated below the IN absolute maximum rating
(Figure 8).
Inrush/Slew-Rate Control
Add a resistor in series with IN to limit transient current
going into the input for the MAX6398 only.
Inrush current control can be implemented by placing a
capacitor at GATE (Figure 7) to slowly ramp up the GATE,
thus limiting the inrush current and controlling GATE’s
slew rate during initial turn-on. The inrush current can be
approximated using the followng formula:
MOSFET Selection
Select external MOSFETs according to the application
current level. The MOSFET’s on-resistance (R
)
DS(ON)
should be chosen low enough to have minimum voltage
drop at full load to limit the MOSFET power dissipation.
Determine the device power rating to accommodate
an overvoltage fault when operating the MAX6397/
MAX6398 in overvoltage-limit mode.
C
OUT
I
=
×I
+ I
GATE LOAD
INRUSH
C
GATE
where I
is GATE’s 75µA sourcing current, I
LOAD
is the load current at startup, and C
GATE
is the output
OUT
capacitor.
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MAX6397/MAX6398
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
V
MAX
V
OV
V
Q1
V
BATT
V
BATT
+
-
GATE
t
2
I
LOAD
IN
GATE
OUT
t
60V
TVS
t
3
1
LOAD
OUT
MAX6397
MAX6398
t
OVP
SET
Figure 10. MAX6397/MAX6398 Timing Diagram
GND
pass transistor and GATE on again after the IC’s junction
temperature cools by 20°C. Thermal-overload protection
is designed to protect the MAX6397/MAX6398 and the
external MOSFET in the event of current-limit fault
conditions. For continuous operation, do not exceed
the absolute maximum junction-temperature rating of
Figure 9. Power Dissipated Across MOSFETs During an
Overvoltage Fault (Overvoltage Limiter Mode)
T = +150°C.
J
During normal operation, the external MOSFETs dissipate
little power. The power dissipated in normal operation is:
Thermal Shutdown
Overvoltage Limiter Mode
P
Q1
= I
2 x R
.
LOAD
DS(ON)
When operating the devices in overvoltage-limit mode
for a prolonged period of time, a thermal shutdown is
possible due to device self-heating. The thermal
shutdown is dependent on a number of different factors:
The most power dissipation will occur during a
prolonged overvoltage event when operating the
MAX6397/MAX6398 in voltage limiter mode, resulting in
high power dissipated in Q1 (Figure 9) where the power
dissipated across Q1 is:
•
•
•
•
•
•
The device’s ambient temperature (T )
A
The output capacitor (C
)
P
Q1
= V x I
Q1 LOAD
OUT
The output load current (I
)
where V is the voltage across the MOSFET’s drain and
Q1
source.
OUT
The overvoltage-threshold limit (V
)
OV
The overvoltage-waveform period (t
)
Thermal Shutdown
OVP
The thermal-shutdown feature of the MAX6397/
MAX6398 shuts off the linear regulator output (REG),
and GATE if it exceeds the maximum allowable thermal
dissipation. Thermal shutdown also monitors the PCB
temperature of the external nFET when the devices sit on
the same thermal island. Good thermal contact between
the MAX6397/MAX6398 and the external nFET is essential
for the thermal-shutdown feature to operate effectively.
Place the nFET as close as possible to OUT.
The power dissipated across the package (P
)
DISS
When OUT exceeds the adjusted overvoltage threshold,
an internal GATE pulldown current is enabled until OUT
drops by 5%. The capacitance at OUT is discharged by
the internal current sink and the external OUT load cur-
rent. The discharge time (∆t1) is approximately:
V
× 0.05
+ I
GATEPD
OV
∆t1 = C
OUT
I
OUT
When the junction temperature exceeds T = +150°C,
J
the thermal sensor signals the shutdown logic, turning
off REG’s internal pass transistor and the GATE output,
allowing the device to cool. The thermal sensor turns the
where V
is the external load current and I
internal 100mA (typ) pulldown current.
is the adjusted overvoltage threshold, I
OV OUT
is the GATE’s
GATEPD
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MAX6397/MAX6398
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
again to the overvoltage threshold can be approximated
using the following formula:
180
I
T
= 0
= +125°C
OUT
THERMAL SHUTDOWN
A
Q
∆V
OUT
I
GATE
170
160
150
140
GD
GS_QGD
∆t3 ≅
×
CGATE = 0
V
where ∆V
= ( V
x 0.05) + ∆V2.
OUT
OV
CGATE = 10nF
The total period of the overvoltage waveform can be
summed up as follows:
CGATE = InF
130
120
CGATE = ADDITIONAL
CAPACITANCE FROM GATE TO GND
t
= ∆t1 + ∆t2 + ∆t3
OVP
The MAX6397/MAX6398 dissipate the most power during
an overvoltage event when I = 0 (C is discharged
1
10
100
1000
OUT
OUT
OUTPUT CAPACITANCE (µF)
only by the internal current sink). The maximum power
dissipation can be approximated using the following
equation:
Figure 11. Junction Temperature vs. C
OUT
When OUT falls 5% below the overvoltage-threshold point,
the internal current sink is disabled and the MAX6397/
MAX6398’s internal charge pump begins recharging
the external GATE voltage. The OUT voltage continues
to drop due to the external OUT load current until the
MOSFET gate is recharged. The time needed to recharge
GATE and re-enhance the external nFET is approximately:
∆t1
P
= V
× 0.975×I
×
GATEPD
DISS
OV
∆t
OVP
The die temperature (T ) increase is related to θ
J
JC
(8.3°C/W and 8.5°C/W for the MAX6397 and MAX6398,
respectively) of the package when mounted correctly
with a strong thermal contact to the circuit board. The
MAX6397/MAX6398 thermal shutdown is governed by
the following equation:
V
+ V
F
GS(TH)
∆t2 = C
ISS
I
GATE
T = T + P
x (θ
+ θ ) < 170°C
J
A
DISS
JC CA
(typical thermal-shutdown temperature)
where C
is the MOSFET’s input capacitance, V
GS(TH)
ISS
is the MOSFET’s gate-to-source threshold voltage, V
F
For the MAX6397, the power dissipation of the internal
linear regulator must be added to the overvoltage-
protection circuit power dissipation to calculate the die
temperature. The linear regulator power dissipation is
calculated using the following equation:
is the internal clamp diode forward voltage (V = 1.5V
F
typ), and I
is the MAX6397/MAX6398 charge-pump
GATE
current (75µA typ).
During ∆t2, C
loses charge through the output load.
OUT
The voltage across C
MOSFET reaches its V
(∆V2) decreases until the
P
= (V − V
) (I
)
OUT
REG
IN
REG REG
threshold and can be
GS(TH)
For example, using an IRFR3410 100V n-channel
MOSFET, Figure 11 illustrates the junction temperature
approximated using the following formula:
∆t2
vs. output capacitor with I
< 16V,V = 1.5V, I
= 0, T = +125°C, V
OUT
A
OV
=
∆V2 = I
OUT
= 75mA, and I
C
F
GATE
GATEPD
OUT
100mA. Figure 11 shows the relationship between output
capacitance versus die temperature for the conditions
listed above.
Once the MOSFET V
output voltage rise is determined by the MOSFET Q
is obtained, the slope of the
GS(TH)
G
charge through the internal charge pump, with respect to
the drain potential. The time for the OUT voltage to rise
Maxim Integrated
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MAX6397/MAX6398
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
OUTPUT Current Calculation
The MAX6397 high input voltage (+72V max) provides
up to 100mA of output current at REG. Package power
dissipation limits the amount of output current available
2.0
1.455W
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
for
a
given input/output voltage and ambient
DERATE 18.2mW/°C
ABOVE +70°C
temperature. Figure 12 depicts the maximum power
dissipation curve for the MAX6397. The graph assumes
that the exposed metal pad of the MAX6397 package is
solderedto1in2ofPCBcopper.UseFigure10todeterminethe
allowable package dissipation for a given ambient
temperature. Alternately, use the following formula to
calculate the allowable package dissipation:
P
DISS
= 1.455W for T ≤ +70°C
A
0
20 40 60 80 100 120 140 160
TEMPERATURE (°C)
Maximum power dissipation = 1.455 - 0.0182 (T - 70°C)
A
for +70°C ≤ T ≤ +125°C
A
where 0.0182 W/°C is the MAX6397 package-thermal
derating.
Figure 12. Maximum Power Dissipation vs. Temperature
After determining the allowable package dissipation,
calculate the maximum output current using the following
formula:
An additional capacitor can be added to GATE and GND
to shift the curves as this increases ∆t1. These values
are used for illustration only. Customers must verify
worst-case conditons for their specific application.
P
DISS
I
=
≤ 100mA
OUT(MAX)
V
− V
REG
IN
Typical Application Circuit
DC-DC
CONVERTER
IN
OUT
µC
GND
GATE
12V IN
IN
OUT
SET
REG
POK
MAX6397
V
CC
SHDN
GND
RESET
GPIO
ALWAYS-ON
µC
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MAX6397/MAX6398
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
Typical Operating Circuit
DC-DC
DC-DC
CONVERTER
CONVERTER
C
OUT
C
OUT
GATE
GATE
V
BATT
V
BATT
IN
OUT
IN
OUT
MAX6397
MAX6398
MAX6397
MAX6398
R1
R2
R1
R2
REG
SET
SET
REG
GND
GND
OVERVOLTAGE LIMITER CONTROLLER
OVERVOLTAGE SWITCH CONTROLLER
Pin Configurations (continued)
Selector Guide
REG OUTPUT POK ASSERTION TOP
VOLTAGE (V) THRESHOLD (%) MARK
PART
TOP VIEW
OUT GATE GND
MAX6397LATA
MAX6397MATA
MAX6397SATA
MAX6397TATA
MAX6397YATA
MAX6397ZATA
MAX6397VATA
MAX6397WATA
MAX6398ATT
5.0
5.0
3.3
3.3
2.5
2.5
1.8
1.8
—
92.5
87.5
87.5
92.5
87.5
92.5
87.5
92.5
—
ANN
ANO
ANQ
ANP
ANK
ANJ
ANM
ANL
AJD
6
5
4
*EP
MAX6398
1
2
3
IN
SHDN SET
TDFN
*EXPOSED PAD. CONNECT TO GND.
Maxim Integrated
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MAX6397/MAX6398
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
Chip Information
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE OUTLINE
LAND PATTERN
NO.
CODE
T633+2
T833+2
NO.
6 TDFN
8 TDFN
21-0137
21-0137
90-0059
90-0058
Maxim Integrated
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MAX6397/MAX6398
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
Revision History
REVISION REVISION
PAGES
CHANGED
DESCRIPTION
NUMBER
DATE
5/05
1/07
3/07
1/09
0
3
4
5
Initial release
—
1, 14, 15, 17
1, 3, 18
3
Changed formula and updated Figure 13 caption title
Updated Electrical Characteristics table.
Updated Electrical Characteristics table.
Deleted automotive references in General Description, Applications, and Detailed
Description sections; deleted Load Dump section and Figure 5 (renumbering the
remaining figures)
6
7/14
1, 7, 10–15
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
©
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
2014 Maxim Integrated Products, Inc.
│ 18
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