MP5991

– 16V, 50A, 1mΩ RDS(ON), HOT-SWAP INTELLI-FUSE SOLUTION

MP5991 Rev. 1.0

MonolithicPower.com

21

4/27/2022

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© 2022 MPS. All Rights Reserved.

OPERATION

The MP5991 is a monolithic Intelli-Fuse device

with

an

integrated,

1mΩ

RDS(ON)

power

MOSFET that is ideally suited for multi-fuse hot-

swap applications. The MP5991 can operate

alone or can be controlled via a hot-swap

controller for multi-fuse operation. It can drive

up to 50A of continuous output current (IOUT) per

device at room temperature, and up to 60A of

continuous IOUT with air flow.

The device limits the backplane voltage drop by

limiting the inrush current to the load while a

circuit card is inserted into a live backplane

power source. It also provides an integrated

current mirror to monitor IOUT and the integrated

on-die temperature sense. This eliminates the

need for an external current-sense power

resistor, power MOSFET, and temperature-

sense device.

The

MP5991

monitors

the

current

and

temperature to feedback information to the

processor or controller. It limits the internal

MOSFET current (IFET) by controlling the gate

voltage (VGATE) via the current limit (ILIMIT)

reference input and soft-start ramp.

MOSFET On/Off Control (ON)

The ON pin turns the power MOSFET on and

off. Pull ON above 1.4V to turn the MOSFET on;

pull ON below 1.2V to turn it off. There is a fixed

tON_DELAY (1.3ms) that starts once ON exceeds

1.4V. The MOSFET remains off until tON_DELAY is

finished. If a fault does not occur, the ON pin

can turn the MOSFET on after 1.3ms. Figure 6

shows the MOSFET on/off control for when

GOK is pulled up to VDD33.

VIN /

VDD33

VON

On

MOSFET

VGOK

Off

>1.4 V

tON_DELAY

On

>1ms

Off

tON_DELAY

Figure 6: MOSFET On/Off Control

If a fault occurs, the GOK is pulled low and the

device shuts down. The fault status is cleared

and GOK is pulled high once ON is pulled low,

regardless of whether the fault is removed. If

the fault is removed while ON is low, pull ON

above 1.4V after a blanking time (tON_BLANK)

(1ms) can start up the device, regardless of

which mode it is in (either latch-off mode or

hiccup mode). Figure 7 shows the MOSFET

on/off control if a fault occurs.

VIN/

VDD33

VON

On

MOSFET

VGOK

Off

>1.4 V

tON_DELAY

On

On

tON_BLANK

Fault

Event

Fault Event

tON_DELAY

tON_DELAY

tON_BLANK

Figure 7: MOSFET On/Off Control if a Fault

Occurs

In standalone mode, the CON can be used for

automatic start-up via the internal

pull-up

current source (4.2µA). If the MP5991 is paired

with an Intelli-Fuse master or controller, then

ON is controlled via the master or controller.

Soft Start (SS)

A soft-start capacitor (CSS) determines the soft-

start time (tSS). If ON is pulled high and tON_DELAY

finishes, a constant-current source proportional

to VIN charges CSS. VOUT rises at a similar slew

rate to VSS.

CSS can be calculated with Equation (1):

( )

( )



=

SS

SS

SS

9 t

ms

C

nF

R

(1)

Where RSS is 0.8MΩ.

For example, a 100nF capacitor sets tSS to

8.9ms. If the load capacitance is extremely

large, the current required to maintain the

preset tSS should exceed the current limit (ILIMIT).