MP2104 – 1.7MHz 600mA SYNCHRONOUS STEP-DOWN CONVERTER

MP2104 Rev. 1.3

www.MonolithicPower.com

6

10/4/2005

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© 2005 MPS. All Rights Reserved.

TM

PIN FUNCTIONS

Pin # Name Description

1

EN

Regulator Enable Control Input. Drive EN above 1.5V to turn on the MP2104. Drive EN below

0.3V to turn it off (shutdown current < 0.1µA).

2

GND Ground.

3

SW

Power Switch Output. Inductor connection to drains of the internal PFET and NFET switches.

4

IN

Supply Input. Bypass to GND with a 2.2µF or greater ceramic capacitor.

5

FB

Feedback Input (MP2104DJ). Connect FB to the center point of the external resistor divider. The

feedback threshold voltage is 0.6V.

5

OUT

Output Voltage Sense Input (MP2104DJ-1.5 and MP2104DJ-1.8). An internal resistor divider is

connected to this pin to set the proper output voltage.

OPERATION

The MP2104 is a constant frequency current

mode PWM step-down converter. The MP2104

is optimized for low voltage, Li-Ion battery

powered applications where high efficiency and

small size are critical. The MP2104 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 MP2104 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

×

≈

×

×

=

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

1.7MHz

OSCILLATOR

IAMP

10X

CURRENT

SENSE

AMP

DH

DL

+

--

MAIN

SWITCH

(PCH)

SYNCHRONOUS

RECTIFIER

(NCH)

MP2104_BD01

Figure 1—Functional Block Diagram (MP2104)