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EV2109DQ-00A

Dual 1.2MHz, 800mA Synchronous Step-Down Converter

Monolithic Power Systems 

MP2109 – DUAL 1.2MHz 800mA SYNCHRONOUS STEP-DOWN CONVERTER

Manufacturer

Coilcraft

Toko

Sumida

Table 2—Suggested Surface Mount Inductors

Part Number

LP03310-222ML

1002AS

CDRH3D16

Inductance (µH)

2.2

2.2

2.2

Max DCR (Ω)

0.15

0.11

0.072

Saturation

Current (A)

1.1

1.14

1.20

Dimensions

LxWxH (mm3)

3.3 x 3.3 x 1

4.6 x 4.6 x 1.2

4 x 4 x 1.8

Table 3—Inductors for Improved Efficiency at 25mA, 50mA, under 100mA Load.

Manufacturer

Coilcraft

Murata

Sumida

Sumida

Part Number

DO1605T-103MX

LQH4C100K04

CR32-100

CR54-100

Inductance (µH)

10

10

10

10

Max DCR (Ω)

0.3

0.2

0.2

0.1

Saturation

Current (A)

1.0

1.2

1.0

1.2

IRMS (A)

0.9

0.8

0.7

1.4

Input Capacitor Selection

The input capacitor reduces the surge current

drawn from the input and switching noise from

the device. The input capacitor impedance at

the switching frequency shall be less than input

source impedance to prevent high frequency

switching current passing to the input. Ceramic

capacitors with X5R or X7R dielectrics are

highly recommended because of their low ESR

and small temperature coefficients. For most

applications, a 4.7µF capacitor is sufficient.

Output Capacitor Selection

The output capacitor keeps output voltage

ripple small and ensures regulation loop stable.

The output capacitor impedance shall be low at

the switching frequency. Ceramic capacitors

with X5R or X7R dielectrics are recommended.

The output ripple ∆VOUT is approximately:

( ) ∆VOUT

≤

VOUT × VIN − VOUT

VIN × fOSC × L

×

⎜⎜⎝⎛ESR

+

8

×

1

fOSC

×

C3

⎟⎟⎠⎞

Thermal Dissipation

Power dissipation shall be considered when

both channels of the MP2109 provide maximum

800mA output current to the loads at high

ambient temperature with low input supply

voltage. If the junction temperature rises above

150°C, the MP2109 two channels will be shut

down.

The junction-to-ambient thermal resistance of

the 10-pin QFN (3mm x 3mm) RΘJA is 50°C/W.

The maximum power dissipation is about 1.6W

when the MP2109 is operating in a 70°C

ambient temperature environment.

PDMAX

=

150o C − 70o C

50o C / W

= 1.6W

PC Board Layout

The high current paths (GND1/GND2, IN1/IN2

and SW1/SW2) should be placed very close to

the device with short, direct and wide traces.

Input capacitors should be placed as close as

possible to the respective IN and GND pins.

The external feedback resistors shall be placed

next to the FB pins. Keep the switching nodes

SW1/SW2 short and away from the feedback

network.

MP2109 Rev.1.4

www.MonolithicPower.com

7

10/16/2006

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