tb62731fug TOSHIBA Semiconductor CORPORATION, tb62731fug Datasheet - Page 5

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

The basic TB62731FUG circuit uses a step-up DC-DC converter and burst control of the current pulse.
Basic Operation
350 kHz) is reached, the transistor is turned off.
decreases, reaching IL = 0.
LED.
The internal MOS transistor (NMOS) is turned on at f
The inductance current IL increases from 0. When IL = ILpeak = 240 mA (typ.) or when 5/6 (83.3%) of f
At that time, the coil maintains IL = ILpeak, the Schottky diode is turned on, and IL = Ic2 flows. Then, Ic2
The above operation repeats. When Ic2 is fully charged, the surplus current becomes I
The graph below shows details of the basic pulse used for burst control.
V
IN
IL, ILpeak
C1
V
CC
SHDN
Figure 2 Switching Waveform of Inductance
With low inductance
350 kHz
REF
OSC
STB
Figure 1 Application Circuit
i (add)
T = 1/f
Maximum duty: 83.3% of f
S
OSC
IL, ILpeak
R
, f
OSC
Q
With high inductance
i (sub)
5
= 350 kHz (typ.)
OSC
Buffer
= 350 kHz, charging energy to the inductor.
OSC
A
GND
A
NMOS
K
Ic2
R_sens
C2
o
, which flows to the
TB62731FUG
I
o
2006-06-14
OSC
(=