FLF3215T-R47N datasheet(13/19 Pages) MICREL

13 / 19 page

Micrel, Inc.

MIC23163/4

July 29, 2013

Revision 2.0

Application Information

The MIC23163/4 is a high-performance DC/DC step-

down regulator offering a small solution size. Supporting

an output current up to 2A inside a tiny 2mm × 2mm DFN

package, the IC requires only three external components

while meeting today’s

miniature portable electronic

device needs. Using the HyperLight Load (HLL) switching

scheme, the MIC23163/4 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 2.2µF ceramic capacitor or greater should be placed

close to the VIN pin and PGND pin for bypassing. A

Murata

GRM188R60J475ME84D,

size

0603,

4.7µF

ceramic

capacitor

recommended

based

performance, size, and cost. 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 MIC23163/4 is designed for use with a 10µF or

greater ceramic output capacitor. Increasing the output

capacitance will lower output ripple and improve load

transient response but could also increase solution size

or cost. A low equivalent series resistance (ESR) ceramic

output

capacitor

such

the

Murata

GRM188R60J106ME84D,

size

0603,

10µF

ceramic

capacitor is 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

the

order

importance):

•

Rated current value

•

Size requirements

•

DC resistance (DCR)

The MIC23163/4 is designed for use with a 0.47µH

inductor. This allows for rapid output voltage recovery

during line and load transients.

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 illustrated in

Equation 2:

























−

OUT

PEAK

Eq. 2

As shown by Equation 2, 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” sections for details.

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

inversely proportional to size, DCR can represent a

significant

efficiency loss.

Refer

the

“Efficiency

Considerations” section for more details.

The transition between high loads (CCM) to HLL mode is

determined by the inductor ripple current and the load

current.

Figure 2. Signals for High-Side Switch Drive (HSD) for TON

Control, Inductor Current, and Low-Side Switch Drive (LSD)

for TOFF Control

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