MAX6397 MAXIM [Maxim Integrated Products], MAX6397 Datasheet

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MAX6397

Manufacturer Part Number
MAX6397
Description
Overvoltage Protection Switch/Limiter Controllers Operate Up to 72V
Manufacturer
MAXIM [Maxim Integrated Products]
Datasheet

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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.
19-3668; Rev 3; 1/07
FireWire is a registered trademark of Apple Computer, Inc.
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.
Automotive
Industrial
FireWire
Notebook Computers
Wall Cube Power Devices
®
________________________________________________________________ Maxim Integrated Products
Overvoltage Protection Switch/Limiter
General Description
Applications
Controllers Operate Up to 72V
Selector Guide and Typical Operating Circuit appear at end
of data sheet.
♦ 5.5V to 72V Wide Supply Voltage Range
♦ Overvoltage Protection Controllers Allow User to
♦ Internal Charge-Pump Circuit Ensures MOSFET
♦ Disconnect or Limit Output from Input During
♦ Adjustable Overvoltage Threshold
♦ Thermal-Shutdown Protection
♦ Always-On, Low-Current (37µA) Linear Regulator
♦ Fully Specified from -40°C to +125°C (T
♦ Small, Thermally Enhanced 3mm x 3mm TDFN
*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.
MAX6397_ATA-T* -40°C to +125°C 8 TDFN-EP**
MAX6398ATT-T*
Pin Configurations continued at end of data sheet.
Size External n-Channel MOSFETs
Gate-to-Source Enhancement for Low R
Performance
Overvoltage Conditions
Sources Up to 100mA (MAX6397)
Package
TOP VIEW
*EXPOSED PAD. CONNECT TO GND.
PART
-40°C to +125°C 6 TDFN-EP**
TEMP RANGE
REG
1
IN
*EP
8
Ordering Information
SHDN
OUT
MAX6397
7
2
TDFN
Pin Configurations
GATE
SET
6
3
GND
POK
4
5
PIN-PACKAGE
Features
J
DS(ON)
)
T833-2
T633-2
CODE
PKG
1

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MAX6397 Summary of contents

Page 1

... MAX6397_ATA-T* -40°C to +125°C 8 TDFN-EP** MAX6398ATT-T* *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 ...

Page 2

... Lead Temperature ................................................................+300° -40°C to +125°C, unless otherwise noted. Typical values are CONDITIONS V IN SHDN = high, no load (MAX6397) SHDN = high, (MAX6398) SHDN = low, no load (MAX6397) SHDN = low, (MAX6398) V rising, enables GATE IN V falling, disables GATE IN V With respect to GND ...

Page 3

... POK Output Low Voltage Note 1: Specifications to -40°C are guaranteed by design and not production tested. Note 2: The MAX6397/MAX6398 power up with the external FET in off mode (V 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. ...

Page 4

... MAX6397 170 160 150 V = 72V 140 IN 130 120 V = 14V IN 110 100 90 80 -50 - 100 125 TEMPERATURE (°C) SHUTDOWN SUPPLY CURRENT vs. INPUT VOLTAGE (MAX6397) 50 REGULATOR ON GATE OFF INPUT VOLTAGE (V) UVLO THRESHOLD vs. TEMPERATURE 6.0 5.8 5.6 5.4 5.2 5.0 4 ...

Page 5

... REG I = 10mA -10 REG -20 -30 -40 -50 -60 -70 10 100 1k 10k 100 125 FREQUENCY (Hz) STARTUP WAVEFORM FROM SHUTDOWN (C = 10µ 10µF) IN OUT MAX6397-98 toc17 R = 100Ω LOAD V SHDN 2V/div V GATE 10V/div V OUT 10V/div I OUT 200mA/div 400µs/div I = 50mA LOAD 100k 1M 10M 5 ...

Page 6

... IN 10V/div 0V V REG 2V/div 0V V POK 2V/div 0A MAX6397-98 toc19 V IN 20V/div V GATE 20V/div V OUT 20V/div V REG 5V/div 1ms/div MAX6397-98 toc21 C = 10µF REG V REG AC-COUPLED 500mV/div I REG 100mA/div 1ms/div MAX6397-98 toc23 V REG 2V/div V POK 2V/div I REG 200mA/div REG 100µs/div ...

Page 7

... 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-low SHDN input to turn off the external MOSFET, disconnecting the load and reducing power consumption. After power is applied and ...

Page 8

... MOSFET and linear regulator if the chip reaches overtemperature conditions. 8 _______________________________________________________________________________________ Linear Regulator (MAX6397 Only) 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 THERMAL regulator operates in an always-on condition regardless PROTECTION of the SHDN logic ...

Page 9

... Overvoltage Protection Switch/Limiter 10ms/div Figure 2a. MAX6397/MAX6398 GATE Waveform During Over- voltage Switch Mode 4ms/div Figure 2b. MAX6397/MAX6398 GATE Waveform During Over- voltage Limit Mode GATE cycles on-off-on-off- sawtooth waveform until OUT remains below the overvoltage fault threshold and GATE remains constantly on (V voltage limiter’ ...

Page 10

... These transients are capable of destroying semicon- ductors on the first ‘fault event.’ 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 6). SET has a rising 1.215V threshold with a 5% falling hysteresis. Begin by selecting the total end-to-end resistance ...

Page 11

... Overvoltage Protection Switch/Limiter GATE IN IN OUT MAX6397 MAX6398 SET GND Figure 6. Setting the MAX6397/MAX6398 Overvoltage Threshold IN GATE V BATT MAX6397 MAX6398 OUT GND (a) 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 ...

Page 12

... V BATT C LOAD OUT 60V TVS Figure 9. Protecting the MAX6397/MAX6398 Input from High- Voltage Transients where I GATE the load current at startup, and C capacitor. When the external MOSFET is turned off during an over- voltage occurrence, stray inductance in the power path may cause voltage ringing exceeding the MAX6397/ MAX6398 absolute maximum input (IN) supply rating ...

Page 13

... The thermal sensor turns the 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 cur- rent-limit fault conditions. For continuous operation, do ...

Page 14

... The MAX6397/MAX6398 thermal shutdown is governed by the equation (typical thermal-shutdown temperature) F For the MAX6397, the power dissipation of the internal linear regulator must be added to the overvoltage pro- GS(TH) tection circuit power dissipation to calculate the die is F temperature. The linear regulator power dissipation is = 1.5V typ), F ...

Page 15

... Figure 13 depicts the maximum power dissipation curve for the MAX6397. The graph assumes that the exposed metal pad of the MAX6397 package is soldered to 1in PC board copper. Use Figure 11 to determine the allow- able package dissipation for a given ambient tempera- ture ...

Page 16

... Typical Operating Circuit DC-DC CONVERTER C OUT V IN BATT R1 R1 SET R2 R2 OVERVOLTAGE SWITCH CONTROLLER PART MAX6397LATA MAX6397MATA MAX6397SATA MAX6397TATA MAX6397YATA MAX6397ZATA MAX6397VATA MAX6397WATA MAX6398ATT TRANSISTOR COUNT: 590 PROCESS: BiCMOS DC-DC CONVERTER C OUT GATE OUT MAX6397 MAX6398 REG GND Selector Guide REG OUTPUT POK ASSERTION TOP ...

Page 17

Overvoltage Protection Switch/Limiter (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) COMMON DIMENSIONS MIN. SYMBOL A 0.70 D 2.90 E 2.90 A1 0.00 L 0.20 ...

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