MP1542 – 700KHz/1.3MHz BOOST CONVERTER WITH A 2A SWITCH

MP1542 Rev. 1.2

www.MonolithicPower.com

5

12/14/2005

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PIN FUNCTIONS

Pin #

Name Description

1

COMP Compensation Pin. Connect a capacitor and resistor in series to ground for loop stability.

2

FB

Feedback Input. Reference voltage is 1.25V. Connect a resistor divider to this pin.

3

EN

Regulator On/Off Control Input. A high input at EN turns on the converter, and a low input turns

6V) for automatic startup. EN cannot be left floating.

4

GND

Ground.

5

SW

Power Switch Output. SW is the drain of the internal MOSFET switch. Connect the power

inductor and output rectifier to SW. SW can swing between GND and 25V.

6

IN

Input Supply Pin. IN must be locally bypassed.

7

FSEL

GND for 700KHz operation.

8

SS

Soft-Start Control Pin. Connect a soft-start capacitor to this pin. The soft-start capacitor is

charged with a constant current of 6µA.

OPERATION

The MP1542 uses a constant frequency, peak

current mode boost regulation architecture to

regulate the feedback voltage.

The

operation

of

the

MP1542

can

be

understood by referring to the block diagram of

Figure 1.

PWM

CONTROL

LOGIC

CURRENT

SENSE

AMP

OSCILLATOR

INTERNAL REGULATOR

AND ENABLE CIRCUITRY

--

+

GM

+

--

GND

FB

COMP

SS

1.25V

SW

IN

--

+

FSEL

EN

MP1542_BD01

4

5

2

1

3

7

8

6

Figure 1—Functional Block Diagram