MPQ4558 – 1A, 2MHz, 55V STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED

MPQ4558 Rev. 1.01

www.MonolithicPower.com

9

5/17/2013

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2013 MPS. All Rights Reserved.

BLOCK DIAGRAM

--

+

LOGIC

--

+

0.5ms SS

SS

COMP

ISW

VIN

BST

SW

FREQ

GND

COMP

FB

EN

SS

0V8

REFERENCE

UVLO

INTERNAL

REGULATORS

OSCILLATOR

Figure 1: Functional Block Diagram

OPERATION

The MPQ4558 is a programmable-frequency,

non-synchronous, step-down, switching regulator

with an integrated high-side, high-voltage power

MOSFET. It provides a single, highly efficient

solution with current-mode control for fast loop

response and easy compensation. It features a

wide input voltage range, internal soft-start

control, and precision current limiting. Its very low

operational quiescent current makes it suitable

for battery-powered applications.

PWM Control Mode

At

moderate-to-high

output

current,

the

MPQ4558 operates in a fixed-frequency, peak-

current–control mode to regulate the output

voltage. The internal clock initiates a PWM cycle.

The power MOSFET turns on and remains on

until its current reaches the value set by the

COMP voltage. When the power MOSFET is off,

it remains off for at least 100ns before the next

cycle starts. If, in one PWM period, the power

MOSFET current does not reach the COMP set

current value, the power MOSFET remains on to

saves on a turn-off operation.

Pulse-Skipping Mode

Under

light-load

condition,

the

switching

frequency drops to zero to reduce switching and

driving losses.

Error Amplifier

The error amplifier compares the FB pin voltage

with the internal reference (REF) and outputs a

current proportional to the difference between the

two. This output current then charges the

external compensation network to form the

COMP voltage, which controls the power

MOSFET current.

While in operation, the minimum COMP voltage

is clamped to 0.9V and its maximum is clamped

to 2.0V. COMP is internally pulled down to GND

in shutdown mode. Avoid pulling COMP up

beyond 2.6V.