+72V, SOT23/TDFN, Simple Swapper Hot-Swap

Controllers

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7

A thermal shutdown feature protects the external MOS-

FET by turning it off if the die temperature of the

MAX5902/MAX5903 exceeds +125°C. The MAX5902/

MAX5903 must be in good thermal contact with the

external MOSFET. See Layout Guidelines in the Appli-

cations section of the data sheet.

A circuit-breaker function monitors the voltage across

circuit-breaker function is enabled after the MOSFET is

fully enhanced. Three threshold voltage options are

available—300mV, 400mV, and 500mV. One version is

available with no circuit-breaker function. Fault man-

agement for the MAX5902/MAX5903 is offered with two

different configurations; latched and automatic retry.

Latched Circuit Breaker

After a circuit-breaker trip event, the latched

versions (MAX5902L/MAX5903L) drive GATE to

(PGOOD) is deasserted. A latched off condition

needs to be reset by toggling ON/OFF low for at

Automatic Retry Circuit Breaker

After a circuit-breaker trip event, the automatic retry

turning off the external MOSFET, and PGOOD

(PGOOD) is deasserted. If the start conditions are met

The start conditions are: the device is not in UVLO;

ON/OFF is not driven low; and the device is not in ther-

mal shutdown.

No Circuit Breaker

For the versions without a circuit breaker, MAX5902N

(MAX5903N), PGOOD (PGOOD) are asserted when the

MOSFET is fully enhanced. Once powered up the

MAX5902N/MAX5903N ignore the MOSFET drain-to-

source voltage for applications where a circuit-breaker

function is not desired.

Applications Information

ON/

OFF Control Input

The ON/OFF control input provides three functions:

external ON/OFF control; setting of the UVLO level; and

resetting after a circuit-breaker event has caused the

MAX5902L/MAX5903L to turn off the external MOSFET.

the MAX5902/MAX5903 to turn off the external MOSFET

(see Figure 3 for a circuit example). To reset the

MAX5902L/MAX5903L after a circuit-breaker event,

ON/OFF can be used to sequence power supplies.

Connecting a capacitor from ON/OFF to GND will delay

the rise of ON/OFF proportional to the capacitance and

input impedance of ON/OFF, typically 33kΩ (Figure 4).

The MAX5902/MAX5903 can be controlled by logic-

level signals. Logic-level signals of 3.3V or 1.8V may be

directly connected to ON/OFF. For 5V logic level control,

insert a series 47kΩ resistor as shown in Figure 5.

Figure 4. Power-Supply Sequencing

HOT-SWAP CONTROLLER #1

GND

C

2C

MAX5902

MAX5903

ON/OFF

HOT-SWAP CONTROLLER #2

GND

GND

MAX5902

MAX5903

ON/OFF

HOT-SWAP CONTROLLER

OPTIONAL

+24V

GND

R2

40.2kΩ

R1

3.01kΩ

MAX5902

MAX5903

GND

DGND

ON/OFF

ON/OFF

Figure 3. Programmed +18V Lockout, with Optional Optocoupler

On/Off Control.