MP2303A – 3A, 28V, 360kHz SYNCHRONOUS RECTIFIED, STEP-DOWN CONVERTER

MP2303A Rev.1.1

www.MonolithicPower.com

8

7/25/2012

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© 2012 MPS. All Rights Reserved.

BLOCK DIAGRAM

INTERNAL

REGULATORS

IN

EN

+

ERROR

AMPLIFIER

1.2V

OVP

RAMP

CLK

0.8V

0.3V

CURRENT

COMPARATOR

CURRENT

SENSE

AMPLIFIER

0.95V

SHUTDOWN

COMPARATOR

COMP

SS

FB

GND

OSCILLATOR

360kHz

S

R

Q

SW

BS

IN

5V

OVP

IN < 3.95V

+

Q

+

+

1.3 V

+

+

+

--

--

--

--

--

--

Figure 1—Functional Block Diagram

OPERATION

FUNCTIONAL DESCRIPTION

The MP2303A is a synchronous rectified,

current-mode, step-down regulator. It regulates

input voltages from 4.7V to 28V down to an

output voltage as low as 0.80V, and supplies up

to 3A of load current.

The MP2303A 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

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 MP2303A FB pin exceeds 20% of the

nominal regulation voltage of 0.80V, the over

voltage comparator is tripped and latched; the

COMP pin and the SS pin are discharged to

GND, forcing the high-side switch off.