MP5075

MP5075 Rev 1.0

www.MonolithicPower.com

10

2/3/2017

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OPERATION

The MP5075 is designed to limit the inrush

current to the load when a circuit card is inserted

into a live backplane power source, thereby

limiting the backplane’s voltage drop and the

slew rate of the voltage to the load. The MP5075

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 switch device.

Enable (EN)

When the input voltage is greater than the under-

voltage lockout (UVLO) threshold (typically 2.6V),

the MP5075 can be enabled by pulling EN above

1.5V. Pull EN down to ground to disable the

MP5075.

Current Limit

The MP5075 provides an internal, fixed, 3A,

constant current limit. Once the device reaches

its current limit threshold, the internal circuit

regulates the gate voltage to hold the current in

the power MOSFET constant. The typical

response time is about 20µs. The output current

may have a small overshoot during this time

period.

If the current limit block starts to regulate the

output current, the power loss on the power

MOSFET causes the IC temperature to rise. If

the junction temperature rises high enough,

thermal shutdown is triggered. After thermal

shutdown occurs, the output is disabled until the

over temperature fault is removed. The over-

temperature threshold is 150°C, and hysteresis

is 30°C.

Short-Circuit Protection (SCP)

If the load current increases rapidly due to a

short circuit, the current may exceed the current

limit threshold greatly before the control loop can

respond. If the current reaches an internal

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

turn-off circuit activates to turn off the power

MOSFET. 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 turn-off is effective, the power MOSFET

remains off

for 80μs. Afterward, the power

MOSFET is turned on again. If the part is still in

the short-circuit condition, the MP5075 enters

current limit until the part is hot enough to trigger

thermal

shutdown.

After

the

short-circuit

condition is removed, the MP5075 auto-retries

after the silicon temperature drops.

Output Discharge

The MP5075 has an output discharge function.

This function can discharge VOUT by the

internal pull-down resistance when the IC is

disabled and the load is very light.

Soft Start (SS)

Soft start prevents large inrush current. The soft-

start time is set to 450

μs internally.

PCB Layout Guidelines

Efficient

PCB

layout

is

critical

for

stable

operation. For best results, refer to Figure 2 and

follow the guidelines below.

1. Place an input capacitor close to VIN.

2. Connect NC to GND for an easier layout.

3. Place enough vias around the IC and enough

copper area near VIN and VOUT to achieve

better thermal performance.

F

igure 2: Recommended Layout