TB62731FUG View Datasheet(PDF) - Marktech Optoelectronics

Part Name

Description

Manufacturer

TB62731FUG

Step-up DC-DC Converter for White LED Driver

Marktech Optoelectronics 

TB62731FUG

Substitute the following conditions in formula 2.

Supply voltage VIN = 3.0~4.3 (V)

Output-side capacitor C2 = 1 (µF) . . . C2 is ignored in the calculation.

Where it is assumed that,

VfLED = 16 (V), Vf schottky = 0.3 (V), R_sens = 1.8 (Ω), Io = 20 (mA), K = 1.1

VfLED: LED Vf

Vf schottky: schottky diode Vf

R_sens: setting resistance

Io: set current

K: margin

L (µH) = ((1.1 × 16 × 0.02) − 3 × 0.02) × (1/275e3) × 2 × (1/(0.21 × 0.21)) = 48.1 (µH, VIN = 3.0 V)

43.8 (µH, VIN = 4.3 V)

Thus, 48.1 (µH) is selected when the input voltage is low, 3.0 V.

Note that the calculation does not consider fluctuations in inductance. Toshiba recommend selection of an

inductance of 1.2 times the calculated value.

The recommended inductance under the above conditions is L (µH) = 48.1 (µH) × 1.2 >= 57.7 (µH).

8

2004-09-14

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