MP2365 – 3A, 28V, 1.4MHz STEP-DOWN CONVERTER

MP2365 Rev. 0.91

www.MonolithicPower.com

5

7/10/2006

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© 2006 MPS. All Rights Reserved.

OPERATION

The MP2365 is a current-mode step-down

regulator. It regulates input voltages from 4.75V to

28V down to an output voltage as low as 0.92V,

and is able to supply up to 3A of load current.

The MP2365 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 error

amplifier.

The

output

current

of

the

transconductance error amplifier is presented at

COMP where a network compensates the

regulation control system. The voltage at COMP

is compared to the switch current measured

internally to control the output voltage.

The converter uses an internal N-Channel

MOSFET switch to step-down the input voltage

to the regulated output voltage. Since the

MOSFET requires a gate voltage greater than

the input voltage, a boost capacitor connected

between SW and BS drives the gate. The

capacitor is internally charged while SW is low.

An internal 10Ω switch from SW to GND is used

to insure that SW is pulled to GND when SW is

low

to

fully

charge

the

LOCKOUT

COMPARATOR

ERROR

AMPLIFIER

FREQUENCY

FOLDBACK

COMPARATOR

INTERNAL

REGULATORS

1.8V

SLOPE

COMP

CLK

CURRENT

COMPARATOR

CURRENT

SENSE

AMPLIFIER

SHUTDOWN

COMPARATOR

COMP

6

IN 2

EN 7

GND

4

SS

8

OSCILLATOR

220KHz/

1.5MHz

S

R

Q

SW

3

BS

1

5V

+

Q

1.2V

+

+

2.60V/

2.39V

+

0.92V

0.6V

+

+

FB

5

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Figure 1—Functional Block Diagram