Application Information(Cont.)

Output Capacitor Selection (Cont.)

For ceramic capacitor application, the output voltage ripple is

ceramic capacitors, the X5R or X7R with their good temperature

and voltage characteristics are recommended.

Setting the LED Current

In figure 1, the converter regulates the voltage on FB pin,

connected with the cathod of the lowest LED and the current-

flowing via the LEDs and the R1, is calculated by the following

equation:

Layout Considerations

For all switching power supplies, the layout is an important step in

the design; especially at high peak currents and switching

frequencies. If the layout is not carefully done, the regulator might

show noise problems and duty cycle jitter.

1. The input capacitor should be placed close to the VIN and

GND. Connecting the capacitor with VIN and GND pins by short

and wide tracks without using any via holes for good filtering and

minimizing the voltage ripple.

2. To minimize copper trace connections that can inject noise into

the system, the inductor should be placed as close as possible to

the LX pin to minimize the noise coupling into other circuits.

3. The feedback network should be routed away from the

inductor. The feedback pin and feedback network should be

shielded with a ground plane or trace to minimize noise coupling

into this circuit.

4. A star ground connection or ground plane minimizes ground

shifts and noise is recommended.

White LED Step-up Converter

2019. 02. 08

12/13

Revision No : 0

FTD8203