STLDC08

Application information

Doc ID 18476 Rev 1

21/29

8.6

Schottky diode selection

Schottky diodes, with their low forward voltage and fast recovery time, are the ideal choice to

maximize efficiency. The output diode in a boost converter conducts current only when the

power switch is OFF. The average current is equal to the output current and the peak current

is equal to the peak inductor current. Ensure that the diode's average and peak current

ratings exceed the average and peak inductor current, respectively. In addition, the diode's

reverse breakdown voltage must exceed the regulator output voltage.

8.7

Input capacitor

The input capacitor of a boost converter is less critical than the output capacitor, due to the

fact that the input current waveform is continuous. The input voltage source impedance

determines the size of the input capacitor, which is typically in the range of 10 µF to 100 µF.

A low ESR capacitor is recommended though it is not as critical as the output capacitor.

8.8

Output capacitor

For best output voltage filtering, a low ESR output capacitor is recommended. Ceramic

capacitors have a low ESR value but tantalum capacitors can be used as well, depending on

the application.

is caused by the charging and discharging process of the output capacitor.

Equation 17

where:

ESR = Output capacitor ESR value

)

PK

(

L

OUT

LED

OUT

I

ESR

C

I

TON

V

×

+

×

=

Δ