MP5981

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

MP5981 Rev. 1.3

MonolithicPower.com

19

5/16/2022

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RON to be 10kΩ. For example, if N is 2, then RPD

can be set to about 22

kΩ.

ON

ON/PD

Controller

MP5981

ON/PD

Control

4.2µA

RON

RPD

VDD3

Control

Logic

10k

Ω

Figure 9: ON/PD Connection for PD Mode

If

ON/PD

is

controlled

by

the

hot-swap

controller and PD mode is not required, remove

RPD and set RON to 0Ω.

GOK Report

GOK is an open-drain, active-low signal that

reports the fault of the Intelli-Fuse. When a fault

occurs, GOK is pulled low. Pull GOK up to the

VDD3 voltage through a 100k

Ω resistor. During

VDD3 power-up, the GOK output is driven low.

Before the power FET is turned on, the GOK

fault condition is detected when VDD3 and VIN

have passed the UVLO threshold. ON/PD is

greater than 1.4V, so the GOK signal is pulled

high if no fault is detected, and is pulled low if a

fault is detected.

There are four fault latch protections for the

MP5981:

1. Over-current protection: When VCS exceeds

the

CLREF

threshold

during

normal

operation, the GOK signal is pulled low after

a 180µs gate regulation time.

2. Short-circuit protection: When the Intelli-

Fuse load current reaches 100A rapidly,

GOK is pulled low immediately.

3. Over-temperature

protection:

Once

the

junction temperature (TJ) exceeds 143°C,

GOK is pulled down.

4. Power FET not fully on indication: After the

FET is enabled and VOUT begins ramping, if

VOUT < 90% of VIN for the maximum soft-

start time (270ms), GOK is driven low. If

VOUT < 1/8 VIN and the FET current is

regulated by VBE for 2.1ms, GOK is driven

low.

When a latch fault occurs, GOK is pulled low.

The GOK fault latch can be released by

recycling VIN.

The MP5981 can detect a power FET drain-to-

source short before the FET is turned on. If a

short is detected, GOK is driven low. Once the

short is removed, GOK is released high again.

Figure 10 shows the power FET on/off control

with the GOK timing diagram when the MP5981

is controlled by the hot-swap controller.

Latch Fault

Occurs

D-S Short

VIN/

VDD33

ON/PD

SWITCH

GOK

Insertion Delay

Remove

Fault

FET Off

FET On

Remove Fault

FET On

Insertion Delay

FET On

Figure 10: Power FET On/Off Control when a

Fault Occurs

Damaged Intelli-Fuse MOSFET Detection

The MP5981 can detect a shorted pass FET

during power-up. Once VDD3 exceeds the

UVLO rising threshold and ON/PD exceeds the

1.4V FET on threshold, the MP5981 detects a

shorted pass FET by treating an output voltage

that exceeds 90% of VIN before the FET turns

on as a short on the MOSFET. The GOK signal

remains low when the MP5981 detects VOUT >

90% of VIN during start-up. Once the short is

removed, and the MP5981 detects that VOUT <

70% of VIN, the GOK signal is released high

again, and the MP5981 prepares for normal

start-up.

D_OC Report

D_OC is an open-drain, active-low output that

reports the over-current warning when VOUT ≥

90% of VIN. Once VCS exceeds 85% of the

CLREF voltage, D_OC is driven low. When VCS

drops below the threshold, D_OC is released

high again. Pull D_OC up to the VDD3 voltage

through a 100k

Ω resistor.

Input and Output Transient Protection

The hot-swap system experiences positive

transients on the input during a hot plug or rapid

turn-off with high current due to parasitic