MP5016 – 2.7 - 15V, 0.7 - 5A, PROGRAMMABLE, CURRENT-LIMITED SWITCH

MP5016 Rev.1.1

www.MonolithicPower.com

12

6/14/2019

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Short-Circuit Protection (SCP)

If the load current increases rapidly due to a

short-circuit event, the current may exceed the

current-limit threshold before the control loop

can respond. If the current reaches the 8A

secondary current limit level, a fast turn-off

circuit activates to turn off the power MOSFET.

This can help limit the peak current through the

switch, keeping the input voltage from dropping

too much. The total short-circuit response time

is about 1µs. After the MOSFET has switched

off, the part restarts. During the restart process,

if the short still exists, the MP5016 regulates the

gate voltage to hold the current at a normal

current limit level. The IC enters hiccup mode

with 2ms of on time and 700ms of off time.

To prevent safe operating area (SOA) damage

during a high input voltage short-circuit

protection (SCP) condition, the IC current limit

folds back when the power MOSFET VDS

voltage is above the typical 11V and the

junction temperature is over 110°C.

Reverse Blocking MOSFET Driver

The MP5016 has a GATE pin to provide an

external N-channel MOSFET gate drive signal

for reverse-current protection (RCP). Three

events can pull down the GATE voltage: VIN

below the under-voltage lockout (UVLO), the

enable (EN) voltage below the low-level

threshold, or thermal shutdown. If any of these

conditions occur, GATE sinks the current from

the gate of the external MOSFET to initiate a

fast turn-off.

For 3.3V low input voltage applications, choose

an external reverse blocking MOSFET with a

small gate threshold voltage (VGSth < 1.6V) to

reduce the voltage drop caused by the reverse-

blocking MOSFET.

Setting an appropriate OVP threshold also can

protect the reverse voltage (from the output to

the input) when using an external N-channel

MOSFET. When VOUT rises too high during

normal operation, the MP5016 SOURCE

voltage is higher than the OVP threshold. In this

case, the GATE voltage is regulated to maintain

the SOURCE clamped at the OVP threshold.

This action protects the reverse current from

the high VOUT to the low VIN.

A 100pF capacitor is required on GATE if it is

not connected to the external MOSFET.

Output Discharge

The MP5016 involves a discharge function that

provides a resistive discharge path for the

external output capacitor. The function is active

when the part is disabled (VIN UVLO, EN

shutdown) and is done in a very limited amount

of time. When using the external reverse-

current block MOSFET, the output discharge

path is blocked by the reverse current block

MOSFET. Therefore, the output cannot be

discharged when the reverse-current block

MOSFET is used.

Enable (EN)

The MP5016 is enabled when EN is high. The

MP5016 is disabled when EN is low. Floating

EN shuts down the MP5016 because there is

an internal 2.2MΩ resistor pulling EN down to

ground. For automatic start-up, connect a pull-

up resistor from VCC to EN.

EN is clamped internally using a 5.5V Zener

diode (see Figure 2). Connecting the EN input

through a pull-up resistor to VCC limits the EN

input current below 100μA to prevent damage

to the Zener diode. For example, when

connecting a 300kΩ pull-up resistor to 15V VCC,

IZener = (15V - 5.5V) / 300kΩ - 5.5V / 2.2MΩ =

29µA.

Figure 2: Zener Diode between EN and GND

When using a pull-up resistor to set the power-

on threshold, avoid using a pull-up resistor that

is too small to increase the operational

quiescent current.