MP5086 –5.5V, 7A, LOW RDSON LOAD SWITCH WITH CURRENT MONITORING AND NTC COMPARATOR

MP5086 Rev.1.0

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12

11/6/2014

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Enable

The enable input will decide the MP5086

operation mode. When input voltage is greater

than

the

under-voltage

lockout

threshold

(UVLO), typically 2.0V and pull EN pin to higher

than 1.2V, MP5086 works in normal mode.

power FET is on.

The all features include

current monitor and NTC protection are active.

Pulling EN down to ground will make MP5086

work in bypass mode.

NTC Protection

MP5086 integrated a NTC comparator to

monitor the system temperature. When NTC pin

open-drain OTP indicator will be pulled high. At

the same time, the OTP pin flag also turn off

main power FET and bypass FET. After that,

MP5086 will enter NTC protection mode and

the OTP pin state is latched.

Current Limit

The MP5086 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 MP5086, and this

values of S 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 raises to high enough,

it will trigger thermal shutdown, and part will

latched. The over temperature threshold is

NTC protection.

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 (typical 13A), 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

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

on power FET. If the part is still in short-circuit

condition. MP5086 will reduce the current limit

to 2/3 of pre-set value, and hold it until the part

is hot enough and thermal shutdown. When the

thermal shutdown is trigged, the part will enter

NTC protection mode.