STLDC08 STMicroelectronics, STLDC08 Datasheet - Page 21

• Manufacturer Part Number: STLDC08
• Description: Step-up controller for LED supply
• Manufacturer: STMicroelectronics

STLDC08
8.6
8.7
8.8
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.
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.
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.
The output voltage ripple consists of two parts, the first is the product I
is caused by the charging and discharging process of the output capacitor.
Equation 17
where:
I
I
C
ESR = Output capacitor ESR value
L(PK)
LED
OUT
= Load current
= Peak current
= Selected output capacitor
Doc ID 18476 Rev 1
Δ
V
OUT
=
TON
C
OUT
×
I
LED
+
ESR
×
I
( L
PK
)
Application information
L(PK)
ESR, the second
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