TB62731FUG View Datasheet(PDF) - Marktech Optoelectronics

Part Name

Description

Manufacturer

TB62731FUG

Step-up DC-DC Converter for White LED Driver

Marktech Optoelectronics 

TB62731FUG

Standby Operation

The SHDN pin is used to set normal or standby operation. When SHDN is set to Low, the operation is

standby; when the pin is High, the LED is turned on. Current consumption in Standby Mode is 1 µA (max).

Output-side capacitor setting

When the output-side capacitor (C2) = 0.1 µF, the peak current to be supplied to LEDs is expected to be the

set current +5~+8 mA.

When C2 = 0.01 µF, the peak current is expected to be the set current +20~30 mA; when C2 = 1 µF, it is the set

current +2~3 mA. Toshiba recommend C2 = 1 µF or more considering the LED max If.

The IC is used only for lighting LEDs. The IC does not finely control output current ripples. This is because

eliminating ripples is considered unnecessary as the LED emittance is recognized as the integral amount.

External inductance setting

The minimum external inductance is calculated as follows:

L (µH) = ((K × Po) − VIN min × Io) × (1/fOSC min) × 2 × (1/Ip min × Ip min) . . . formula 2

The above parameters are described below:

Po: output power (power required by LED load)

Po (W) = Vf LED × If LED + Vf schottky × If LED + R_sens × If LED × If LED

LED forward current: If LED (mA) = Set current: Io (mA), LED forward voltage: Vf LED (V),

schottky diode forward voltage: Vf schottky (V),

Setting resistance: R_sens (Ω)

VIN min (V): minimum input voltage (battery voltage)

If the input voltage includes a resistance component, take the voltage drop into consideration for the

minimum input voltage.

The input current IIN is roughly estimated as follows:

IIN (mA) = VfLED × Io × (1/η) × (1/VIN) . . . formula 3

When min VIN = 3.2 (V), VfLED = 16 (V), Io = 18 (mA), and η >= 75 (%), then IIN = 0.12 (mA). As a result,

the voltage drops by 1.2 V due to the 1-Ω DC resistance component. Because the IC’s minimum VCC =

3.0 V, the minimum VIN is 3.12 V (VIN >= 3.12 V).

Io (A): Mean current value set according to resistance R_sens (Ω)

fOSC (Hz): Switching frequency of internal MOS transistor

Specified values for fOSC (kHz): 275 min, 350 typ., 475 max

Ip (A): Peak current value supplied to external inductor

Specified values for Ip (A): 230 min, 240 typ., 270 max

K: Margin of output power K = 1.1~1.3

The ideal condition is to give 1.05 to 1.3 times the output power Po as the input power.

The loss of the IC is assumed to be included in the margin.

If K is too large, it may not be possible for the current characteristic to be the specified value. Note that

K > 1.

7

2004-09-14

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