MP5991

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

MP5991 Rev. 1.0

MonolithicPower.com

29

4/27/2022

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APPLICATION INFORMATION

Selecting the Current-Limit Resistor (RCS)

The MP5991

’s over current limit (ILIMIT) should

exceed the normal ILOAD_MAX. This allows for

tolerances in the current-sense value. ILIMIT can

be calculated with Equation (10):

( )

= 5

OCREF

LIMIT

CS

V

I

10 A

R

(10)

Where VOCREF is the OCREF voltage while

the MOSFET operates in linear mode.

If RCS is 3kΩ and VOCREF is 1.2V, then ILIMIT is

40A. If VOCREF is 0.3V, then ILIMIT is 10A.

Current-Limit Reference Voltage (OCREF)

The OCREF pin sets the current-limit reference

via the hot-swap controller in slave mode or via

a resistor connected to ground in standalone

mode. IOCREF (10μA) sets VOCREF in standalone

mode. Place a 1nF to 10nF capacitor between

the OCREF and GND pins to reduce noise and

maintain a smooth indicator voltage.

During normal operation, VOCREF can be set

between 0.3V and 1.8V to configure ILIMIT either

low or high while RCS is fixed.

Current Monitor Setting (IMON)

The

MP5991

provides

a power MOSFET

current-monitoring function. Connect a resistor

(RIMON) between the IMON and GND pins to set

the IOUT gain.

In a single-fuse application, RIMON should be

≥RCS. If the device is used in a multi-fuse

parallel application, the start-up current balance

per device can be achieved by connecting the

IMON pins together.

The

equivalent

average

IMON

resistance

(RIMON_AVG) can be calculated with Equation (6).

Figure 16 shows the IMON and CS connections

of multiple MP5991s in a multi-fuse parallel

application.

MP5991

MP5991

MP5991

IMON

IMON

GND

CS

IMON

RCS

GND

CS

RCS

GND

CS

RCS

N

R

R

CS

IMON_AVG =

RIMON

RIMON

RIMON

RIMON = RCS

Figure 16: IMON and CS Connections in Multi-

Fuse Parallel Application

Maximum Output Current

The MP5991 can drive up to 50A of continuous

IOUT per device at room temperature, and up to

60A IOUT with air flow. Figure 17 shows the case

temperature rise at different air flow conditions.

10

30

50

70

90

110

30

35

40

45

50

55

60

OUTPUT CURRENT (A)

No Air Flow

Air Flow=100ft/min

Air Flow=200ft/min

Figure 17: Case Temperature Rise