MP2131 – 4A, 5.5V, 1.2MHZ SYNCHRONOUS STEP-DOWN SWITCHER

MP2131 Rev.1.0

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12

5/6/2015

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to ground by an internal MOSFET. The

MOSFET as a maximum Rdson of less than

100 Ω.

Current Limit

The MP2131 has a typical 7.5 A current limit for

the HS-FET and a 3.5 A current limit for the LS-

FET. Once the HS-FET hits the current limit,

the HS-FET is turned off, and the LS-FET is

turned on, reducing the inductor current. The

LS-FET is turned off if the current drops to the

valley current limit, which turns on the HS-

FET. If the HS-FET hits the peak current limit

and the LS-FET hits the valley current limit

every cycle for 150 µs, the MP2131 will remain

at the hiccup threshold until the current

decreases. This prevents the inductor current

from continuing to build up, which results in

damage to the components.

Short Circuit and Recovery

If the output voltage of the buck converter is

shorted to GND, the current limit is triggered.

Once the current limit is triggered every cycle

for 150 µs, the MP2131 enters hiccup mode;

the MP2131 disables the output power stage,

discharges the soft-start capacitor, and then

automatically tries to soft-start again. If the

short-circuit condition still holds after the soft-

start ends, the MP2131 repeats this operation

cycle until the short circuit is removed, and the

output rises back to the regulation level.