MP5981

– 16V, 50A, 1.1mΩ RDS(ON), HOT-SWAP INTELLI-FUSE SOLUTION

MP5981 Rev. 1.3

MonolithicPower.com

22

5/16/2022

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APPLICATION INFORMATION

Current Limit Resistor (RCS)

The MP5981

’s normal current limit value should

be greater than the normal maximum load

current, allowing the tolerances in the current

sense value. The current limit can be calculated

with Equation (10):

(A)

10

R

V

I

5

CS

CLREF_NORM

LIMIT



=

(10)

Where VCLREF_NORM is the CLREF voltage when

the power FET works in linear mode, and RCS is

the resistor from CS to ground

(Ω).

If RCS is set to 3kΩ, and VCLREF_NORM is 1.2V, the

desired current limit is about 40A. When

VCLREF_NORM is 0.3V, the desired current limit is

about 10A.

Note that the maximum CS resistor (RCS)

should be set no higher than 3.6

kΩ.

CLREF

CLREF sets the current-limit reference voltage,

which can be determined by the hot-swap

controller or a resistor to ground in standalone

operation. A CLREF 10µA current source sets

the pin voltage. Place a 1nF capacitor from

CLREF to ground to smooth the indicator

voltage if the MP5981 is in standalone mode.

For the current limit at normal operation, the

CLREF voltage can be set from 0.3V to 1.6V to

program the current limit low or high while a

fixed RCS resistor is used.

Current Monitor Set (IMON)

The

MP5981

provides

a power MOSFET

current-monitoring function. Place a resistor to

ground to set the gain of the output current.

In a single-MP5981 application, the IMON

resistor should be set no lower than the CS

resistor. When the MP5981 is used in a multi-

fuse

parallel

application,

achieve

start-up

current balance per device by connecting IMON

and CS (see Figure 14).

The

equivalent

average

IMON

resistor

(RIMON_AVG) can be calculated with RCS / N,

where N is the active parallel number.

MP5981

MP5981

MP5981

IMON

IMON

GND

CS

IMON

RCS

GND

CS

RCS

GND

CS

RCS

N

R

R

CS

IMON_AVG =

RIMON

RIMON

RIMON

RIMON = RCS

Figure 14: Multi-MP5981 IMON and CS

Connection in Parallel Application

Maximum Output Current

The MP5981 drives up to 50A of continuous

current per device at room temperature, and

can reach 60A with air flow. Figure 15 shows

the case temperature rise vs. the output current

at different air conditions.

0

20

40

60

80

100

120

30

35

40

45

50

55

60

OUTPUT CURRENT (A)

No Air Flow

Air Flow=100ft/min

Air Flow=200ft/min

Figure 15: Output Current Derating Curve