tb62732fug TOSHIBA Semiconductor CORPORATION, tb62732fug Datasheet - Page 6

• Manufacturer Part Number: tb62732fug
• Description: Step-up Dc/dc Converter For White Led Driver
• Manufacturer: TOSHIBA Semiconductor CORPORATION

Pin A
voltage
Pin K
tvoltage
IF current
C2 = 0.1 µF
20 mA/DIV
State of Peak Current Control
The current pulse in Figure 2 is a charging current on the output side capacitor C
as a C2 discharge current and flows through the R_sens resistor to GND.
obtained decreases the peak current to an assumed value of approximately 48 to 54 mV.
to 10 µH, the boost inductor has been optimally designed for this load power of 320 mW.
should be strictly maintained.
0.5 V/DIV
“Peak current control” is control that can vary the peak current pulse shown in Figure 2 on the previous page.
The charging voltage wave form of C
In the internal circuit to which it is assumed pin K is input, the mean value of the AC voltage waveform
As a result, a constant current is controlled as an average current in the LED.
Therefore, if R_sens = 2.7 Ω is connected, an I
The TB62732FUG is designed to be able to supply a load power of 320 mW (min.). With an inductance of 4.7
Also, make the inductance small when the load power is low.
A condition applying to the LED load between pins A and K is that
The LED will be illuminated always regardless of the IC control. Care should be taken in this regard.
5 V/DIV
Maximum On pulse
width = 85%
LED V
Pin A voltage
I
Pin A current (external
inductance current)
Pin K voltage (current
charged on capacitor)
A
V
(peak)
IN
F
(V
CC
) < LED V
F
Figure 3 Burst Control Waveforms
total
t
2
Switching frequency
f
is fed back to the IC from pin K.
OSC
= 1.1 MHz
200 ns/DIV
F
current of 19.6 mA can be obtained.
6
Standby Operation
operation. When SHDN is set to Low, operation is in
standby; when the pin is High, the LED is turned on.
Current consumption in Standby Mode is 1 µA (max).
Drive Waveform
the coil of the generator terminal (pin A), the
feedback voltage wave form of pin K, and the LED
I
F
The SHDN pin is used to set normal or standby
The figure on the left is an actual drive waveform.
From the top, the switching voltage waveform of
.
As I
I
As I
I
o
o
..
.
A
A
2
(peak) is lowered, it is stabilized at the set value
(peak) is lowered, it is stabilized at the set value
. This is supplied to the LED
TB62732FUG
2006-06-14