MP2105 – 1MHz 800mA SYNCHRONOUS STEP-DOWN CONVERTER

MP2105 Rev. 1.2

www.MonolithicPower.com

5

8/19/2005

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© 2005 MPS. All Rights Reserved.

TM

OPERATION

The MP2105 is a constant frequency current

mode PWM step-down converter. The MP2105

is optimized for low voltage, Li-Ion battery

powered applications where high efficiency and

small size are critical. The MP2105 uses an

external resistor divider to set the output

voltage from 0.6V to 6V. The device integrates

both a main switch and a synchronous rectifier,

which provides high efficiency and eliminates

an external Schottky diode. The MP2105 can

achieve 100% duty cycle. The duty cycle D of a

step-down converter is defined as:

%

100

V

V

%

100

f

T

D

IN

OUT

OSC

ON

×

≈

×

×

=

is the oscillator frequency (1MHz).

IN

EN

FB

GND

SW

+

+

--

PWMCMP

PWM

OSC

+

--

EAMP

ICS

SLOPE COMP

FEEDBACK

ERROR\

AMP

0.6V

EAO

CC

17pF

BIAS

&

VOLTAGE

REFERENCE

PWM

CONTROL

LOGIC

1.0MHz

OSCILLATOR

IAMP

10X

CURRENT

SENSE

AMP

DH

DL

+

--

MAIN

SWITCH

(PCH)

SYNCHRONOUS

RECTIFIER

(NCH)

MP2105_BD01

Figure 1—Functional Block Diagram