MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED

MPQ2451 Rev 1.02

www.MonolithicPower.com

9

5/3/2013

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© 2013 MPS. All Rights Reserved.

OPERATION

The MPQ2451 is a 2MHz, non-synchronous,

step-down switching regulator with an integrated

high-side high voltage power MOSFET. It

provides

an

internally-compensated,

highly-

efficient output of up to 0.6A with current mode

control. It also features wide input voltage range,

internal soft-start control, and a precision current

limit. Its very low operational quiescent current

makes

it

suitable

for

battery-powered

applications.

PWM Control

At

moderate-to-high

output

current,

the

MPQ2451 operates in a fixed-frequency peak-

current–control mode to regulate the output

voltage. A PWM cycle—initiated by the internal

clock—turns the power MOSFET on, and the

MOSFET remains on until its current reaches the

value set by COMP voltage. When the PWM

signal goes low, the power switch turns off and

remains off for at least 100ns before the next

cycle starts.

If the current in the power MOSFET does not

reach COMP set current value within one PWM

cycle, the power MOSFET remains on to avoid a

turn-off operation.

Pulse-Skipping Mode

Under light-load conditions, the MPQ2451 goes

into pulse-skipping mode to improve efficiency.

Pulse-skipping triggers when the COMP voltage

drops below the internal sleep threshold, which

generates a PAUSE command to block the turn-

on clock pulse so the power MOSFET does not

turn ON; this procedure reduces gate driving and

switching losses. This PAUSE command causes

the whole chip to enter sleep mode, reducing the

quiescent current to further improve the light load

efficiency.

When the COMP voltage exceeds the sleep

threshold, the PAUSE signal resets and the chip

resumes normal PWM operation. Whenever the

PAUSE changes state from low to high, the PWM

signal immediately goes HIGH and turns on the

power MOSFET.

Error Amplifier

The error amplifier is composed of an internal op-

amp with an RC feedback network connected

between its output node (internal COMP node)

and its negative input node (FB). When the FB

voltage drops below the internal reference

output high, causing a higher switch peak current

output and delivering more energy to the output.

Conversely, when the FB voltage rises above

When using the FB pin, connect to the tap of a

to control the gain of the error amplifier in

addition to the internal compensation RC network.

Internal Regulator

The 2.6V internal regulator powers most of the

input and operates in the full VIN range. When

below 3.0V, the output degrades.

Enable Control

The MPQ2451 has a dedicated enable control

pin can enable or disable the chip for HIGH

effective logic. Its falling threshold is 1.2V, and its

rising threshold is about 1.6V. When floated, the

EN pin is internally pulled down to GND to

disable the.

When the EN voltage is pulled to 0V, the chip

enters the lowest shutdown current mode. When

the EN voltage rises above 0V but lower than

rising threshold, the chip remains in shutdown

mode with a slightly higher shutdown current.

Under Voltage Lockout (UVLO)

chip from operating at an insufficient supply

voltage.

The

UVLO

rising

threshold

is

approximately 2.9V while its falling threshold is

2.6V.