MP1591 – 2A, 32V, 330KHz STEP-DOWN CONVERTER

MP1591 Rev. 2.1

www.MonolithicPower.com

4

12/5/2005

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TM

OPERATION

The MP1591 is a current mode step-down

regulator. It regulates input voltages from 6.5V

to 32V down to an output voltage as low as

1.230V and is able to supply up to 2A of load

current.

The MP1591 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

the switch is off to fully charge the BS capacitor.

MP1591_BD01

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

OSCILLATOR

35/330KHz

S

R

Q

SW

3

BS

M1

M2

1

+

REF

5V

8

Q

1.2V

+

+

2.60V/

2.35V

+

1.230V

0.7V

+

+

FB

5

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Figure 1—Functional Block Diagram