MPQ4462 – 3.5A, 4MHz, 36V, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED

MPQ4462 Rev. 1.11

www.MonolithicPower.com

10

7/17/2013

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© 2013 MPS. All Rights Reserved.

OPERATION

The

MPQ4462

is

a

variable-frequency,

asynchronous, step-down switching regulator

with an integrated, high-side, high-voltage,

power MOSFET. It provides a highly efficient

output with current mode control for fast loop

response and easy compensation. It features a

wide input-voltage range, internal soft-start

control, and precise current limiting. Its very-low

operational quiescent current makes it suitable

for battery-powered applications.

PWM Control

At

moderate-to-high

output

current,

the

MPQ4462 operates in a fixed-frequency, peak-

current-control mode to regulate the output

voltage. The internal clock initiates a PWM

cycle that turns the power MOSFET on. This

MOSFET remains on until its current reaches

MOSFET is off, it remains off for at least 100ns

before the next cycle starts. If the current in the

power MOSFET does not reach the COMP set

current value within one PWM period, the

power MOSFET remains on to save a turn-off

operation.

Error Amplifier

reference

proportional to the difference between the two.

This output current charges the external

controls the power MOSFET current.

to 0.9V and its maximum is clamped to 2.0V.

COMP is internally pulled down to GND in

shutdown mode. COMP should not be pulled up

beyond 2.6V.

Internal Regulator

The 2.6V internal regulator powers most of the

exceeds 3.0V, the output of the regulator is in

full regulation. When VIN falls below 3.0V, the

output decreases.

Enable Control

The MPQ4462 has a dedicated enable-control

pin (EN). Enable uses logic-high to enable and

disable the chip. Its falling threshold is precisely

1.2V, and its rising threshold is 1.5V (300mV

higher).

When floating, EN is pulled up to about 3.0V by

an internal 1µA current source to remain

enabled. To pull-down requires a 1µA current.

enters its lowest shutdown current mode. When

threshold, the chip remains in shutdown mode

but the shutdown current increases slightly.

Under-Voltage Lockout (UVLO)

Under-voltage lockout (UVLO) protects the chip

from operating at insufficient supply voltages.

The UVLO rising threshold is about 3.0V while

its falling threshold is a consistent 2.6V.

Internal Soft-Start

The soft-start prevents the converter output

voltage from overshooting during startup. When

the chip starts, the internal circuitry generates a

the reference.

Thermal Shutdown

Thermal shutdown prevents the chip from

operating at exceedingly high temperatures.

When the die temperature exceeds its upper

threshold, the chip shuts down. When the

temperature falls below its lower threshold, chip

function resumes.

Floating Driver and Bootstrap Charging

An external bootstrap capacitor powers the

floating power MOSFET driver. This floating

driver has its own UVLO protection, with a

UVLO rising threshold of 2.2V with a falling

threshold of 150mV.

A dedicated, internal, bootstrap regulator

charges and regulates the bootstrap capacitor

~5V. When the voltage between the BST and

SW nodes falls below its regulation voltage, a

PMOS pass transistor connected from VIN to

BST turns on. The current-charging path is VIN

→

BST → SW. The external circuit should

provide enough voltage headroom to facilitate

charging.