MP5921

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

MP5921 Rev. 1.1

www.MonolithicPower.com

20

5/17/2022

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ON

ON/PD

Controller

MP5921

ON/PD

Control

4.2µA

RON

RPD

VDD3

Control

Logic

Figure 9: ON/PD Connection for PD Mode

If the ON/PD is controlled by the hot-swap

controller

and

PD

mode

is

unnecessary,

remove RPD and connect ON/PD to the hot-

swap controller with a

10kΩ resistor.

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

higher than 1.4V, so the GOK signal is pulled

high if no fault is detected or is pulled low if a

fault is detected.

There are four fault latch protections for the

MP5921.

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) is higher than

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%VIN for the maximum soft-start

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

1/8VIN, 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 MP5921 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 MP5921

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 MP5921 can detect a shorted pass FET

during power-up. Once VDD3 is higher than the

UVLO rising threshold, and ON/PD is higher

than the 1.4V FET on threshold, the MP5921

detects a shorted pass FET by treating an

output voltage that exceeds 90%VIN before the

FET turns on as a short on the MOSFET. The

GOK signal remains low when the MP5921

detects VOUT > 90%*VIN during start-up. Once

the short is removed, and the MP5921 detects

that VOUT < 70%*VIN, the GOK signal is

released high again, and the MP5921 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%VIN. Once VCS is higher than 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.