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.