MP2108 – 2A, 6V, 740KHz SYNCHRONOUS BUCK CONVERTER

MP2108 Rev 1.1

www.MonolithicPower.com

3

10/2/2006

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© 2006 MPS. All Rights Reserved.

Parameter

Symbol Condition

Min

Typ

Max

Units

Oscillator

Switching Frequency

620

740

920

KHz

Maximum Duty Cycle

85

%

Minimum On Time

200

ns

Error Amplifier

Voltage Gain

400

V/V

Transconductance

450

µA/V

COMP Maximum Output Current

±40

µA

FB Regulation Voltage

875

895

915

mV

FB Input Bias Current

–100

nA

Soft-Start

Soft-Start Current

2

µA

Output Switch On-Resistance

190

mΩ

Switch On Resistance

280

mΩ

160

mΩ

Synchronous Rectifier On Resistance

230

mΩ

Switch Current Limit (Source)

2.5

3.5

A

Synchronous Rectifier Current Limit

(Sink)

350

mA

Thermal Shutdown

160

°C

PIN FUNCTIONS

Pin #

Name

Description

1

BST

Power Switch Boost. BST powers the gate of the high-side N-Channel power MOSFET

switch. Connect a 10nF or greater capacitor between BST and LX.

2

VIN

Internal Power Input. VIN supplies the power to the MP2108 through the internal LDO

regulator. Bypass VIN to PGND with a 10µF or greater capacitor. Connect VIN to the input

source voltage.

3

LX

Output Switching Node. LX is the source of the high-side N-Channel switch and the drain

of the low-side N-Channel switch. Connect the output LC filter between LX and the output.

4

PGND

Power Ground. PGND is the source of the N-Channel MOSFET synchronous rectifier.

Connect PGND to SGND as close to the MP2108 as possible.

5

SGND

Signal Ground.

6

SS

Soft-Start Input. Place a capacitor from SS to SGND to set the soft-start period. The

MP2108 sources 2µA from SS to the soft-start capacitor at start-up. As the voltage at SS

rises, the feedback threshold voltage increases to limit inrush current at startup.

7

FB

Feedback Input. FB is the inverting input of the internal error amplifier. Connect a resistive

voltage divider from the output voltage to FB to set the output voltage.

8

COMP

Compensation Node. COMP is the output of the error amplifier. Connect a series RC

network to compensate the regulation control loop.

9

VREF

Internal 2.4V Regulator Bypass. Connect a 10nF capacitor between VREF and SGND to

bypass the internal regulator. Do not apply any load to VREF.

10

RUN

On/Off Control Input. Drive RUN high to turn on the MP2108, drive RUN low to turn the

MP2108 off. For automatic startup, connect RUN to VIN via a 100kΩ pull-up resistor.