MP2212 – 16V, 3A, 600kHz SYNCHRONOUS STEP-DOWN CONVERTER

MP2212 Rev. 1.01

www.MonolithicPower.com

10

2/22/2012

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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. If

electrolytic capacitor is used, pay attention to

output ripple voltage, extra heating, and the

selection of feedback resistor R1 (refer to “Output

Voltage Setting” section) due to large ESR of

approximately:

OUT

IN

OUT

OUT

IN

OSC

OSC

Vx(V

V

)

1

V

x(ESR

)

V xf

xL

8xf

xC3

−

Δ≤

+

The output capacitance is recommended to be

less than 100μF.

External Schottky Diode

For this part, an external schottky diode is

recommended to be placed close to "SW" and

"GND" pins, especially when the output current is

larger than 2A.

With the external schottky diode, the voltage

spike and negative kick on "SW" pin can be

minimized; moreover, the conversion efficiency

can also be improved a little.

For the external schottky diode selection, it's

noteworthy that the maximum reverse voltage

rating of the external diode should be larger than

the maximum input voltage. As for the current

rating of this diode, 0.5A rating should be

sufficient.

PCB Layout Guide

PCB layout is very important to achieve stable

operation. It is highly recommended to duplicate

EVB layout for optimum performance. If change

is necessary, please follow these guidelines as

follows. Here, the typical application circuit is

taken as an example to illustrate the key layout

rules should be followed.

1) For MP2212DQ, a PCB layout with more than

(or) four layers is recommended.

2) The high current paths (GND, IN and SW)

should be placed very close to the device with

short, direct and wide traces.

3) For MP2212DQ, two input ceramic capacitors

(2 x (10μF~22μF)) are strongly recommended to

be placed on both sides of the MP2212DQ

package and keep them as close as possible to

the “IN” and “GND” pins.

For MP2212DN, an input ceramic capacitor

should be placed as close as possible to “IN” and

“GND” pins.

4) A RC low pass filter is recommended for VCC

placed as close as possible to “VCC” pin and

“GND” pin.

5) The external feedback resistors shall be

placed next to the FB pin. Keep the FB trace as

short as possible.

6) Keep the switching node SW short and away

from the feedback network.

Top Layer

Inner Layer1