MP1586 – 3A, 28V, 50kHz TO 400kHz STEP-DOWN CONVERTER

MP1586 Rev. 0.91

www.MonolithicPower.com

7

1/8/2010

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BLOCK DIAGRAM

--

+

--

+

1.5ms SS

Gm Error Amp

SS

2.6V

5V

COMP

VIN

BST

SW

GND

FREQ

COMP

FB

EN

SS

0V8

REFERENCE UVLO/

THERMAL

SHUTDOWN

INTERNAL

REGULATORS

OSCILLATOR

--

+

SW

--

+

Level

Shift

CLK

Figure 1—Function Block Diagram

OPERATION

The MP1586 is a non-synchronous, step-down

switching regulator with an integrated high-side

high voltage power MOSFET. It provides a

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

At moderate to high output current, the MP1586

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 the

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 the

COMP set current value, the power MOSFET

remains on, saving a turn-off operation.