MP4566―36V, 1MHz, 0.6A, STEP-DOWN CONVERTER WITH 35μA QUIESCENT CURRENT

MP4566 Rev. 1.01

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8

9/22/2011

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0.5ms SS

REFERENCE

UVLO

INTERNAL

REGULATOR

OSCILLATOR

2MHz

LOGIC

SW

VIN

EN

FB

GND

ISW

ISW

SS

COMP

SS

1.0V

BIAS

BST

Figure 1—Functional Block Diagram

OPERATION

The MP4566 is a 1MHz, non-synchronous, step-

down switching regulator with integrated internal

high-side high voltage power MOSFET. It

provides internally compensated single 0.6A

highly efficient output with current mode control.

It features wide input voltage range, internal soft-

start control, and precision current limit. Its very

low operational quiescent current suits it for

battery powered applications.

PWM Control

At moderate to high output current, the MP4566

operates in a fixed frequency, peak current

control mode to regulate the output voltage. A

PWM cycle is initiated by the internal clock. The

power MOSFET is turned on and remains on

until its current reaches the value set by COMP

voltage. When the power switch is off, it remains

off for at least 100ns before the next cycle starts.

If, in one PWM period, the current in the power

MOSFET does not reach COMP set current

value, the power MOSFET remains on, saving a

turn-off operation.

Pulse Skipping Mode

At light load condition, the MP4566 goes into

pulse skipping mode to improve light load

efficiency. Pulse skipping decision is based on its

internal COMP voltage. If COMP is lower than

the internal sleep threshold, a PAUSE command

is generated to block the turn-on clock pulse so

the power MOSFET is not commanded ON

subsequently, saving gate driving and switching

losses. This PAUSE command also puts the

whole chip into sleep mode, consuming very low

quiescent current to further improve the light load

efficiency.

When COMP voltage is higher than the sleep

threshold, the PAUSE signal is reset so the chip

is back into normal PWM operation. Every time

when the PAUSE changes states from low to

high, a turn-on signal is generated right away,

turning on the power MOSFET.