MAX6397 查看數據表（PDF） - Maxim Integrated

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MAX6397

Overvoltage Protection Switch/Limiter Controllers Operate Up to 72V

Maxim Integrated 

Overvoltage Protection Switch/Limiter

Controllers Operate Up to 72V

PIN

MAX6397 MAX6398

1

1

2

2

3

3

4

—

5

4

6

5

7

6

8

—

—

—

Pin Description

NAME

IN

SHDN

SET

POK

GND

GATE

OUT

REG

EP

FUNCTION

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.

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.

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.

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.

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.

Detailed Description

The MAX6397/MAX6398 are ultra-small, low-current,

high-voltage protection circuits for automotive applica-

tions that must survive load dump and 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 con-

troller allows system designers to size the external

MOSFET to their load current and board size.

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

threshold, GATE pulls to OUT, turning off

the MOSFET.

The MAX6397/MAX6398 are configurable to operate as

overvoltage protection switches or as closed-looped volt-

age limiters. In overvoltage protection switch mode, the

input voltage is monitored. When an overvoltage condi-

tion occurs at IN, GATE pulls low, disconnecting the load

from the power source, and then slowly enhances upon

removal of the overvoltage condition. In overvoltage

limit mode, the output voltage 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-low 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.

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