MIC23201 datasheet(13/20 Pages) MICREL

13 / 20 page

Micrel Inc.

MIC23201

August 2012

M9999-082912-A

Application Information

The MIC23201 is a high performance DC/DC step down

regulator offering a small solution size. Supporting an

output current up to 2A inside a tiny 3mm x 3mm MLF

package and requiring only three external components,

the MIC23201 is able to maintain high efficiency

throughout the entire load range while providing ultra-

fast load transient response. The following sections

provide additional device application information.

Input Capacitor

A minimum of 4.7µF ceramic capacitor or greater should

be placed close to the VIN pin and PGND / GND pin for

bypassing but the recommended value of input capacitor

is 22µF. A X5R or X7R temperature rating is

recommended for the input capacitor. Y5V temperature

rating capacitors, aside from losing most of their

capacitance over temperature, can also become

resistive at high frequencies. This reduces their ability to

filter out high frequency noise.

Output Capacitor

The MIC23201 was designed for use with a minimum of

4.7µF or greater ceramic output capacitor. Increasing the

output capacitance will lower output ripple and improve

load transient response but could increase solution size

or cost. The recommended value of output capacitor is

22µF. A low equivalent series resistance (ESR) ceramic

output

capacitor

recommended

based

upon

performance, size and cost. Both the X7R or X5R

temperature rating capacitors are recommended. The

Y5V and Z5U temperature rating capacitors are not

recommended due to their wide variation in capacitance

over temperature and increased resistance at high

frequencies.

Inductor Selection

When selecting an inductor, it is important to consider

the following factors (not necessarily in the order of

importance):



Inductance



Rated current value



Size requirements



DC resistance (DCR)

The MIC23201 was designed for use with a 1µH to

2.2µH inductor. For faster transient response, a 1µH

inductor will yield the best result. For lower output ripple,

a 2.2µH inductor is recommended.

Maximum current ratings of the inductor are generally

given in two methods; permissible DC current and

saturation current. Permissible DC current can be rated

either for a 40°C temperature rise or a 10% to 20% loss

in inductance. Ensure the inductor selected can handle

the maximum operating current. When saturation current

is specified, make sure that there is enough margin so

that the peak current does not cause the inductor to

saturate. Peak current can be calculated as follows:

































OUT

PEAK

As shown by the calculation above, the peak inductor

current is inversely proportional to the switching

frequency and the inductance; the lower the switching

frequency or the inductance the higher the peak current.

As input voltage increases, the peak current also

increases.

The size of the inductor depends on the requirements of

the application. Refer to the Typical Application Circuit

and Bill of Materials for details.

DC resistance (DCR) is also important. While DCR is

inversely proportional to size, DCR can represent a

significant efficiency loss. Refer to the Efficiency

Considerations.

Compensation

The MIC23201 is designed to be stable with a 1µH to

2.2µH inductor with a minimum of 4.7µF ceramic (X5R)

output capacitor.

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