Application Information

Input Capacitor Selection

the input supply and reduces noise injection into the IC. The

reflected ripple voltage will be smaller with larger CIN. For reliable

operation, it is recommended to select the capacitor voltage

rating at least 1.2 times higher than the maximum input voltage.

The capacitors should be placed close to the VIN and GND.

Inductor Selection

For high efficiencies, the inductor should have a low dc

resistance to minimize conduction losses. Especially at

high-switching frequencies the core material has a higher impact

on efficiency. When using small chip inductors, the efficiency is

reduced mainly due to higher inductor core losses. This needs to

be considered when selecting the appropriate inductor. The

inductor value determines the inductor ripple current. The larger

the inductor value, the smaller the inductor ripple current and the

lower the conduction losses of the converter. Conversely, larger

inductor values cause a slower load transient response. A

50% of the average inductor current. The recommended inductor

value can be calculated as below:

where

η

= Efficiency

typical)

To avoid saturation of the inductor, the inductor should be rated

at least for the maximum input current of the converter plus the

inductor ripple current. The maximum input current is calculated

as below:

The peak inductor current is calculated as the following equation:

Output Capacitor Selection

The current-mode control scheme of the FTD8203 allows the usage

of tiny ceramic capacitors. The higher capacitor value provides

good load transient response.Ceramic capacitors with low ESR

values have the lowest output voltage ripple and are

recommended. If required,tantalum capacitors may be used as

well. The output ripple is the sum of the voltages across the ESR

and the ideal output capacitor.

White LED Step-up Converter

2019. 02. 08

11/13

Revision No : 0

FTD8203