MIC2145_05 Datasheet, PDF (8/15 Pages) Micrel Semiconductor – High Efficiency 2.5W Boost Converter

MIC2145
Application Information
Pre-designed circuit information is at the end of this section.
Output Voltage
The output voltage of the regulator can be set between 2.4V
and 16V by connecting a resistor divider at the FB pin. The
resistor values are selected by the following equations:
R2= ^{1.08V ∑R1}
V_OUT − 1.08V
Micrel, Inc.
A value of 1MΩ is recommended for R1 to minimize the
quiescent current when the part is off. Then, R2 can be solved
using the above equation. A feed-forward capacitor, C_FF,
ranging from 5pF to 100pF can be used in parallel with R1 to
reduce the peak-to-peak output voltage ripple, which is
shown in Figures 4 and 5.
V_OUT
AC Couple
(100mV/div)
V_SW
(5V/div)
Time 20µs
Figure 4. Without Feed-Forward Capacitor
V_OUT
AC Couple
(100mV/div)
V_SW
(5V/div)
Time 4µs
Figure 5. With Feed-Forward Capacitor (100pF)
M9999-042205
8
April 2005