MP2307 – 3A, 23V, 340KHz SYNCHRONOUS RECTIFIED STEP-DOWN CONVERTER

MP2307 Rev. 1.7

www.MonolithicPower.com

6

3/14/2006

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© 2006 MPS. All Rights Reserved.

TM

OPERATION

FUNCTIONAL DESCRIPTION

The MP2307 regulates input voltages from

4.75V to 23V down to an output voltage as low

as 0.925V, and supplies up to 3A of load

current.

The MP2307 uses current-mode control to

regulate the output voltage. The output voltage

is measured at FB through a resistive voltage

divider and amplified through the internal

transconductance error amplifier. The voltage at

the COMP pin is compared to the switch current

(measured internally) to control the output

voltage.

The

converter

uses

internal

N-Channel

MOSFET switches to step-down the input

voltage to the regulated output voltage. Since

the high side MOSFET requires a gate voltage

greater than the input voltage, a boost capacitor

connected between SW and BS is needed to

drive the high side gate. The boost capacitor is

charged from the internal 5V rail when SW is low.

When the FB pin voltage exceeds 20% of the

nominal regulation value of 0.925V, the over

voltage comparator is tripped and the COMP

pin and the SS pin are discharged to GND,

forcing the high-side switch off.

MP2307_BD01

LOCKOUT

COMPARATOR

INTERNAL

REGULATORS

IN

EN

+

ERROR

AMPLIFIER

1.2V

OVP

RAMP

CLK

0.925V

7V

0.3V

CURRENT

COMPARATOR

CURRENT

SENSE

AMPLIFIER

1.1V

SHUTDOWN

COMPARATOR

7

COMP 6

SS 8

FB 5

GND

4

OSCILLATOR

110/340KHz

S

R

Q

SW

3

BS

1

IN

5V

2

OVP

IN < 4.10V

EN OK

Zener

+

Q

+

+

1.5V

+

+

2.5V

+

+

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Figure 1—Functional Block Diagram