MAX6399 データシートの表示（PDF） - Maxim Integrated

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MAX6399

High-Voltage, Overvoltage/Undervoltage, Protection Switch Controller

Maxim Integrated 

High-Voltage, Overvoltage/Undervoltage,

Protection Switch Controller

Pin Description

PIN

NAME

FUNCTION

1

IN

Supply Voltage Input. Bypass with a 10µF capacitor (minimum).

Shutdown Input. Drive SHDN low to force GATE low, turning off the external n-channel MOSFET. SHDN is

2

SHDN internally pulled down to GND with a 1µA current source. Toggle SHDN to unlatch GATE after an

overvoltage condition. Connect to IN for normal operation.

Overvoltage Threshold Adjustment Input. Use SET to monitor a system output voltage. Connect SET to an

3

SET external resistor voltage-divider network to adjust the desired overvoltage limit threshold. GATE is quickly

turned off when SET rises above its 0.5V (typ) threshold.

4

POK Power-OK Open-Drain Output. POK asserts low when OUT_SET falls below its 1.23V (typ) threshold.

5

GND Ground

Gate-Drive Output. Connect GATE to the gate of an external n-channel FET. GATE is a charge pump with a

6

GATE

100µA pullup current to IN + 10V (typ) during normal operation. GATE is quickly turned off during an

overvoltage condition. GATE remains latched off until the power is recycled or SHDN is toggled. GATE pulls

low when SHDN is low.

7

OUT Output Voltage-Sense Input. Connect to the source of the external n-channel MOSFET.

Undervoltage Detector Input. Use OUT_SET to monitor the source of the MOSFET. Connect a

8

OUT_SET resistor-divider from OUT to OUT_SET to adjust the desired undervoltage threshold. POK asserts low

when OUT_SET falls below its 1.23V threshold.

—

EP Exposed Pad. Connect to ground plane.

IN

UVLO

5V

SET

0.5V

MAX6399

1.23V

OUT_SET

Figure 1. Functional Diagram

THERMAL

PROTECTION

CHARGE

PUMP

GATE

OUT

SHDN

POK

GND

Detailed Description

The MAX6399 is an ultra-small, low-current protection

circuit utilized in DC-DC converter applications. The

MAX6399 monitors the input and output voltages of a

DC-DC converter for undervoltage and overvoltage

conditions. The MAX6399 controls an external n-chan-

nel MOSFET to isolate the load during an overvoltage

condition. The device allows system designers to size

the external n-channel MOSFET to their load current

and board size.

The MAX6399 drives the MOSFET’s gate high when the

monitored DC-DC output voltage is below the program-

mable overvoltage threshold, programmed through

SET. An internal charge-pump circuit provides a guar-

anteed 10V gate-to-source drive to ensure low input-to-

load voltage drops in normal operating modes. When

the monitored DC-DC output voltage rises above the

user-adjusted overvoltage threshold, GATE latches low,

turning off the MOSFET. The MOSFET remains off until

the power is recycled or by toggling SHDN.

The MAX6399 also monitors for an undervoltage condi-

tion at the input of the DC-DC converter through

OUT_SET. An active-high, open-drain, power-good out-

put can be used to drive the EN input, notifying the sys-

tem when the monitored voltage is below the adjusted

undervoltage voltage threshold.

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