tb62731fug TOSHIBA Semiconductor CORPORATION, tb62731fug Datasheet - Page 7

• Manufacturer Part Number: tb62731fug
• Description: Step-up Dc-dc Converter For White Led Driver
• Manufacturer: TOSHIBA Semiconductor CORPORATION

Standby Operation
standby; when the pin is High, the LED is turned on. Current consumption in Standby Mode is 1 µA (max).
Output-side capacitor setting
set current +5~+8 mA.
current +2~3 mA. Toshiba recommend C2 = 1 µF or more considering the LED max If.
eliminating ripples is considered unnecessary as the LED emittance is recognized as the integral amount.
External inductance setting
The SHDN pin is used to set normal or standby operation. When SHDN is set to Low, the operation is
When the output-side capacitor (C2) = 0.1 µF, the peak current to be supplied to LEDs is expected to be the
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
The IC is used only for lighting LEDs. The IC does not finely control output current ripples. This is because
The minimum external inductance is calculated as follows:
The above parameters are described below:
L (µH) = ((K × P
P
I
f
Ip (A): Peak current value supplied to external inductor
K: Margin of output power K = 1.1~1.3
OSC
o
o
: output power (power required by LED load)
(A): Mean current value set according to resistance R_sens ( Ω )
P
LED forward current: If LED (mA) = Set current: I
schottky diode forward voltage: Vf schottky (V),
Setting resistance: R_sens (Ω)
V
If the input voltage includes a resistance component, take the voltage drop into consideration for the
minimum input voltage.
The input current I
When min V
the voltage drops by 1.2 V due to the 1- Ω DC resistance component. Because the IC’s minimum V
3.0 V, the minimum V
Specified values for f
Specified values for Ip (A): 230 min, 240 typ., 270 max
The ideal condition is to give 1.05 to 1.3 times the output power P
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.
(Hz): Switching frequency of internal MOS transistor
o
IN
(W) = Vf LED × If LED + Vf schottky × If LED + R_sens × If LED × If LED
min (V): minimum input voltage (battery voltage)
I
IN
(mA) = VfLED × I
o
) − V
IN
= 3.2 (V), VfLED = 16 (V), I
IN
IN
min × I
OSC
IN
is roughly estimated as follows:
is 3.12 V (V
(kHz): 275 min, 350 typ., 475 max
o
o
) × (1/f
× (1/η) × (1/V
OSC
IN
min) × 2 × (1/Ip min × Ip min) . . . formula 2
> = 3.12 V).
IN
o
= 18 (mA), and η > = 75 (%), then I
) . . . formula 3
7
o
(mA), LED forward voltage: Vf LED (V),
o
as the input power.
IN
= 0.12 (mA). As a result,
TB62731FUG
2006-06-14
CC
=