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PDF MAX6398 Data sheet ( Hoja de datos )
| Número de pieza | MAX6398 | |
| Descripción | (MAX6397 / MAX6398) Overvoltage Protection Switch/Limiter Controllers Operate Up to 72V | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MAX6398 (archivo pdf) en la parte inferior de esta página. Total 17 Páginas | ||
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19-3668; Rev 3; 1/07
www.DataSheet4U.com
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
General Description
The MAX6397/MAX6398 are small, high-voltage overvolt-
age protection circuits. These devices disconnect the
output load or limit the output voltage during an input
overvoltage condition. These devices are ideal for appli-
cations that must survive high-voltage transients such as
those found in automotive and industrial applications.
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.
When the input voltage exceeds the overvoltage thresh-
old, 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.
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.
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.
The MAX6397/MAX6398 include internal thermal-shut-
down 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.
Applications
Automotive
Industrial
FireWire®
Notebook Computers
Wall Cube Power Devices
FireWire is a registered trademark of Apple Computer, Inc.
Features
♦ 5.5V to 72V Wide Supply Voltage Range
♦ Overvoltage Protection Controllers Allow User to
Size External n-Channel MOSFETs
♦ Internal Charge-Pump Circuit Ensures MOSFET
Gate-to-Source Enhancement for Low RDS(ON)
Performance
♦ 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 (TJ)
♦ Small, Thermally Enhanced 3mm x 3mm TDFN
Package
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
PKG
CODE
MAX6397_ATA-T* -40°C to +125°C 8 TDFN-EP** T833-2
MAX6398ATT-T* -40°C to +125°C 6 TDFN-EP** T633-2
*Replace “-T” with “+T” for lead-free 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.
Selector Guide and Typical Operating Circuit appear at end
of data sheet.
Pin Configurations
TOP VIEW
REG OUT GATE GND
876 5
*EP
MAX6397
1234
IN SHDN SET POK
TDFN
*EXPOSED PAD. CONNECT TO GND.
Pin Configurations continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1 page  
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
Typical Operating Characteristics (continued)
(VIN = 14V, CREG = 4.7µF, IREG = 0, unless otherwise noted.)
GATE-TO-OUT CLAMP VOLTAGE
vs. TEMPERATURE
17.0
16.9
16.8
16.7
16.6
16.5
16.4
16.3
16.2
16.1
16.0
-50 -25
0 25 50 75 100 125
TEMPERATURE (°C)
MAXIMUM REG OUTPUT VOLTAGE
vs. LOAD CURRENT AND TEMPERATURE
5.2
TA = -40°C
5.0
4.8
TA = +25°C
4.6
TA = +125°C
4.4 THERMAL
SHUTDOWN
4.2
4.0
0 40 80 120 160 200 240 280 320 360 400
LOAD CURRENT (mA)
DROPOUT VOLTAGE
vs. REG LOAD CURRENT
2.0
MAX6397L
1.8
1.6
1.4 TA = +125°C
1.2
1.0
0.8
0.6 TA = +25°C
0.4
TA = -40°C
0.2
0
0 20 40 60 80 100 120 140 160 180
REG LOAD CURRENT (mA)
10.500
10.495
10.490
10.485
10.480
10.475
10.470
10.465
10.460
10.455
10.450
-50
GATE-DRIVE VOLTAGE
vs. TEMPERATURE
-25 0 25 50 75 100
TEMPERATURE (°C)
125
REG OUTPUT VOLTAGE
vs. LOAD CURRENT AND TEMPERATURE
5.20
MAX6397L
5.15
5.10
ILOAD = 10mA
5.05 ILOAD = 50mA
5.00
4.95 ILOAD = 100mA
4.90
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
0
CREG = 10µF
-10 IREG = 10mA
-20
-30
-40
-50
-60
-70
10 100 1k 10k 100k 1M 10M
FREQUENCY (Hz)
STARTUP WAVEFORM
(RLOAD = 100Ω, CIN = 10µF, COUT = 10µF)
MAX6397-98 toc16
VIN
10V/div
STARTUP WAVEFORM FROM SHUTDOWN
(CIN = 10µF, COUT = 10µF)
MAX6397-98 toc17
RLOAD = 100Ω
VSHDN
2V/div
VGATE
10V/div
VGATE
10V/div
4ms/div
VOUT
10V/div
IOUT
200mA/div
400µs/div
VOUT
10V/div
IOUT
200mA/div
_______________________________________________________________________________________ 5
5 Page 
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
GATE
IN IN
OUT
MAX6397
MAX6398 SET
R1
GND R2
Figure 6. Setting the MAX6397/MAX6398 Overvoltage Threshold
GATE
IN IN
OUT
R1
MAX6397
SET MAX6398
R2 GND
Q1
VBATT
IN
GATE
MAX6397
MAX6398
OUT
GND
LOAD
VBATT
IN
GATE
MAX6397
MAX6398
OUT
GND
LOAD
(a) (b)
Figure 7. Reverse Battery Protection Using a Diode or p-Channel MOSFET
Reverse-Battery Protection
Use a diode or p-channel MOSFET to protect the
MAX6397/MAX6398 during a reverse-battery insertion
(Figures 7a, 7b). 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 7a) thus improving efficiency.
Connecting a positive battery voltage to the drain of Q1
(Figure 7b) produces forward bias in its body diode,
which clamps the source voltage one diode drop below
the drain voltage. When the source voltage exceeds
Q1’s threshold 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.
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 bat-
tery from the system. The zener diode and resistor com-
bination prevent damage to the p-channel MOSFET
during an overvoltage condition.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet MAX6398.PDF ] | |
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