General Description

The MAX5921/MAX5939 hot-swap controllers allow a cir-

cuit card to be safely hot plugged into a live backplane.

The MAX5921/MAX5939 operate from -20V to -80V and

are well suited for -48V power systems. These devices

are pin compatible with both the LT1640 and LT4250 and

provide improved features over these devices.

The MAX5921/MAX5939 provide a controlled turn-on to

circuit cards preventing damage to board connectors,

board components, and preventing glitches on the

power-supply rail. The MAX5921/MAX5939 provide

undervoltage, overvoltage, and overcurrent protection.

These devices ensure that the input voltage is stable

and within tolerance before applying power to the load.

Both the MAX5921 and MAX5939 protect a system

against overcurrent and short-circuit conditions by turn-

ing off the external MOSFET in the event of a fault con-

dition. The MAX5921/MAX5939 protect against input

voltage steps by limiting the load current to a safe level

without turning off power to the load.

The device features an open-drain power-good status

output, PWRGD or PWRGD for enabling downstream

converters (see Selector Guide). A built-in thermal shut-

down feature is also included to protect the external

MOSFET in case of overheating. The MAX5939 features

a latched fault output. The MAX5921 contains built-in

autoretry circuitry after a fault condition.

The MAX5921/MAX5939 are available in an 8-pin SO

package and operate in the extended -40°C to +85°C

temperature range.

Applications

Telecom Line Cards

Network Switches/Routers

Central-Office Line Cards

Server Line Cards

Base-Station Line Cards

Features

o Allows Safe Board Insertion and Removal

from a Live -48V Backplane

o Pin-Compatible with LT1640 and LT4250

o Circuit Breaker Immunity to Input Voltage Steps

and Current Spikes

o 450mA GATE Pulldown Current During Short-

Circuit Condition

o Exponential GATE Pulldown Current

o Withstands -100V Input Transients with No

External Components

o Programmable Inrush and Short-Circuit Current

Limits

o Operates from -20V to -80V

o Programmable Overvoltage Protection

o Programmable Undervoltage Lockout

with Built-In Glitch Filter

o Overcurrent Fault Integrator

o Powers Up into a Shorted Load

o Power-Good Control Output

o Thermal Shutdown Protects External MOSFET

-48V Hot-Swap Controllers with External

________________________________________________________________ Maxim Integrated Products

1

GATE

SENSE

1

2

8

7

DRAIN

OV

UV

PWRGD

(PWRGD)

SO

TOP VIEW

3

4

6

5

MAX5921

MAX5939

() FOR MAX5921B/F AND MAX5939B/F.

Pin Configuration

Ordering Information

19-2946; Rev 0; 9/03

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.

PART

TEMP RANGE

PIN-PACKAGE

MAX5921AESA

-40°C to +85°C

8 SO

MAX5921BESA

-40°C to +85°C

8 SO

Typical Operating Circuit and Selector Guide appear at end

of data sheet.

Ordering Information continued at end of data sheet.