MIC23163 Datasheet, PDF (13/19 Pages) Micrel Semiconductor – 4MHz, 2A, 100% Duty Cycle Buck Regulator with HyperLight Load® and Power Good

Micrel, Inc.
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 is recommended based on
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 as 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 in the order of
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.
MIC23163/4
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:
I_PEAK

= _I_OUT

+
V_OUT

1
− V_OUT /V_IN
2×f ×L

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 to 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
July 29, 2013
13
Revision 2.0