MP5083

– 5.5V, 2A LOW RDSON LOAD SWITCH WITH CURRENT MONITORING

MP5083 Rev. 1.1

www.MonolithicPower.com

11

7/12/2017

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2017 MPS. All Rights Reserved.

OPERATION

The MP5083 is designed to limit the in-rush

current

to

the

load

thereby

limiting

the

backplane’s voltage drop and the slew rate of

the voltage to the load. It provides an integrated

solution to monitor the input voltage, output

voltage and output current to eliminate the need

for an external current power MOSFET, and

current sense device.

Enable

When input voltage is greater than the under-

voltage lockout threshold (UVLO), typically 0.5V,

MP5083 can be enabled by pulling EN pin to

higher than 1.5V. Pulling down to ground or

floating will disable MP5083.

Current Limit

The MP5083 provides a constant current limit

that can be programmed by an external resistor.

Once the device reaches its current limit

threshold, the internal circuit regulates the gate

voltage to hold the current in the power FET

constant. The typical response time is about

20µs and the output current may have a small

overshoot during this time period.

The

pre-set

current

limit

value

can

be

calculated by below equation:

(1)

S is the current sense ratio of MP5083, and this

is almost a constant value when Vin is changing

from 1.2V to 5.5V, and when Vin is smaller than

1.2V, a step change will come to S value, the

value will change from 33000 to about 28000.

Meanwhile, when Vcc is changing, there is also

a little shift on S value, for more information,

please refer the curves in typical performance

characteristics.

If the current limit block starts to regulate the

output current, the power loss on power

MOSFET will cause the IC temperature rise. If

the junction temperature rose to high enough, it

will trigger thermal shutdown. After thermal

shutdown happened, it will disable the output

until the over temperature fault remove. The

over

temperature threshold

is

150°C and

hysteresis is 30°C.

Power-Good Function

The PG pin is the push pull of a MOSFET that

the PG pin is pulled high after a 50µs delay.

When the voltage gap is higher than 340mV,

the PG pin will be pulled low.

Short-Circuit Protection

If the load current increases rapidly due to a

short circuit, the current may exceed the current

limit threshold by a lot before the control loop

can respond. If the current reaches an internal

secondary current limit level (about 7A), a fast

turn-off circuit activates to turn off the power

FET. This limits the peak current through the

switch to limit the input voltage drop. The total

short circuit response time is about 200ns. If

fast off works, it will keep off the power FET for

80µs. After that time period, it will re-turn on

power FET, if the part is still in short-circuit

condition. MP5083 will reduce the current limit,

and hold it until the part is so hot and thermal

shutdown.

After

the

short-circuit

condition

removed, the current limit will recover to the

pre-set value automatically.

Output Discharge

MP5083 has output discharge function. This

function can discharge the Vo by internal pull

shutdown and the load is very light.

Soft-Start

A capacitor connected to the SS pin determines

the soft-start time. There is an internal 11µA

constant current source charge SS cap and

ramps up the voltage on the SS pin. The output

voltage rises at 5 times the slew rate to the SS

voltage.

The soft-start time can be calculated by below

equation:

)

(

)

(

)

(

5

1

)

(

uA

I

nF

C

V

V

ms

T

SS

SS

OUT

SS







(2)

The suggestion minimum SS cap should be

bigger than 4.7nF. If the SS pin is floated or SS

limited

by

power

MOS

charge

time.