MP2143H – 3A, 5.5V, 2.0MHz, SYNCHRONOUS STEP-DOWN SWITCHER

MP2143H Rev. 1.02

www.MonolithicPower.com

11

6/30/2016

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© 2016 MPS. All Rights Reserved.

OPERATION

The MP2143H uses constant-on-time control

with input-voltage feed-forward to stabilize the

switching frequency over its full input range. It

can achieve up to 3A continuous output current

from a 2.5V to 5.5V input voltage with excellent

load and line regulation. The output voltage can

be regulated as low as 0.6V.

Constant-On-Time Control

When compared to fixed-frequency PWM control,

constant on-time control offers a simpler control

loop and faster transient response. By using

input-voltage

feed-forward,

the

MP2143H

maintains a nearly constant switching frequency

across the entire input and output voltage range.

The switching pulse ON time can be estimated as:

To prevent inductor current runaway during the

load transient, the MP2143H has a fixed minimum

OFF time of 50ns. However, this minimum OFF

time limit does not affect the operation of the

MP2143H in steady state in any way.

Enable

When the input voltage exceeds the under-

voltage lockout (UVLO) threshold—typically

2.2V—the MP2143H is enabled by pulling the

EN pin above 1.2V. Leaving the EN pin floating

or grounded will disable the MP2143H. There is

an internal 1MΩ resistor from the EN pin to

ground.

Soft-Start/Stop

MP2143H has a built-in soft-start that ramps up

the output voltage at a constant slew rate that

avoids overshooting at startup. The soft-start

time is typically about 1.3ms. When disabled,

the

MP2143H

ramps

down

the

internal

reference voltage to allow the load to linearly

discharge the output.

Power Good Indicator

MP2143H has an open drain with 500kΩ pull-up

resistor pin for power good (PG) indication.

When the FB pin is within ±10% of regulation

voltage (0.6V), the PG pin is pulled up to VIN by

the internal resistor. If the FB pin voltage is

outside the ±10% window, the PG pin is pulled

to ground by an internal MOSFET. The

100Ω.

Current Limit

The MP2143H has a 4.8A current limit for the

high side switch (HS-FET). When the HS-FET

hits its current limit, the MP2143H enters hiccup

mode until the current drops to prevent the

inductor current from building and possibly

damaging the components.

Short Circuit and Recovery

The

MP2143H

also

enters

short-circuit

protection (SCP) mode when it hits the current

limit, and tries to recover from the short circuit

by entering hiccup mode. In SCP, the

MP2143H disables the output power stage,

discharges a soft-start capacitor, and then

enacts a soft-start procedure. If the short-circuit

condition still holds after soft-start ends, the

MP2143H repeats this operation until the short

circuit ceases and output rises back to

regulation level.