April 2005 11 M9999-042205
MIC2145 Micrel, Inc.
Diode
A Schottky diode should be used for the output diode. Most
of the application circuits on this data sheet specify the
Motorola MBR0530 surface mount Schottky diode. It has a
forward current of 0.5A and a low forward voltage drop. For
applications that are cost driven, the 1N4148 or equivalent
can be used but the efficiency will suffer due to higher forward
voltage drop.
Output Capacitor
Low ESR capacitors should be used at the output of the
MIC2145 to minimize the switching output ripple voltage.
Selection of the capacitor value will depend upon the peak
inductor current, inductor size, and the load. MuRata offers
the GRM43-2 series with up to 10µF at 25V, with a X5R
temperature coefficient in a 1812 surface-mount package.
For lower output voltage applications, the GRM42-2 (1210
package/10µF/16V) and GRM42-6 (1206 package/10µF/
6.3V) series can be used. Typically, values ranging from
10µF to 47µF can be used for the output capacitor.
Reducing Peak Current
If lower than 400mA peak current is required then the soft
start pin may be shorted to ground. This changes the refer-
ence of the current limit comparator. With the soft start pin
shorted to ground, the maximum current will approximately
reduce to half. The peak current should always be set at least
50% higher than the maximum load current.
