MIC2250_10 Datasheet, PDF (10/13 Pages) Micrel Semiconductor – High-Efficiency Low EMI Boost Regulator

Micrel, Inc.
saturation current rating of the selected inductor should
be 20-30% higher than the 2A specification for proper
operation.
Figure 2. Efficiency Comparison between Lower
and Higher Inductor Values
Input Capacitor
The boost converter exhibits a triangular current
waveform at its input, so an input capacitor is required to
decouple this waveform and thereby reduce the input
voltage ripple. A 10uF to 22uF ceramic capacitor should
be sufficient for most applications. A minimum input
capacitance of 1uF is recommended. The input capacitor
should be as close as possible to the inductor and the
MIC2250, with short PCB traces for good noise
MIC2250
performance.
Output Capacitor
Output capacitor selection is also a trade-off between
performance, size, and cost. Increasing C_OUT will lead to
an improved transient response however the size and
cost also increase. X5R and X7R ceramic capacitors are
recommended. For most applications, 2.2uF to 22uF
should be sufficient.
Diode
The MIC2250 requires an external diode for operation.
The diode must be rated for the peak inductor current,
and its reverse voltage rating must be greater than the
output voltage. A Schottky diode is recommended for
lower output voltages due to its lower forward voltage
drop and reverse recovery time. However, at higher
output voltages (>10V), a high speed diode such as
LS4148 can be more efficient as it has the advantage of
considerably lower leakage currents, especially at higher
temperatures. This will greatly improve light load
efficiency when compared to a Schottky diode.
For example: At 70^oC ambient temperature, V_IN = 2.5V,
V_OUT= 24V at no load.
Input current (Vishay SL04 Schottky) = 2.1mA
Input current (Generic LS4148) = 0.37mA
May 2010
10
M9999-051310-A