tb62732fug TOSHIBA Semiconductor CORPORATION, tb62732fug Datasheet - Page 8

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

Selection of R_sens
current I
is possible that the current IF LED will not exceed a given value.
peak value of 380 mA, make sure that the inrush current I
Protection for when the LED is open
LED is open.
Figure 4, and to use a zener diode with lower power dissipation.
(R_sens = 2.7 Ω)
Toshiba recommend 100 Ω or less.
The resistance R_sens (Ω) between pin K and GND is used for setting the output current I
The mean current I
For example, if R_sens = 2.7 (Ω), then I
The IC has a minimum output P
In this case, if the product Po of the set current I
If the IC is not connected to the smoothing capacitor, then I
In this instance, because the current which flows to the LED is a triangular waveform current with a maximum
Toshiba recommend use of components with low reactance (parasitic inductance) and minimized PCB wiring.
The zener diode in the example application circuit in Figure 1 is necessary for over-voltage protection when the
It is strongly recommended that a zener diode be connected since this driver lacks a voltage protection circuit.
The zener voltage should satisfy the following conditions:
Moreover, it is possible to control the output current IZD for when the LED is open by connecting the R_ZD as in
Standard for Control of Output Current IZD through R_ZD Connection
Since driver characteristics may be adversely affected,
i)
ii)
iii)
R_DZ (Ω)
O
I
Number of LEDs
≤ maximum output voltage of the TB62732FUG
≥ LED aggregate V
≤ maximum output capacitance C
o
can be set using this resistance.
100
(mA) = V (K): pin K feedback voltage (mV) ÷ R_sens Ω)
18
2
3
4
O
(mA) to be set is roughly calculated as follows:
f
IZD (mA)
0.1
3
o
= 320 (mW).
Pin K voltage
O
V (K)
48
50
52
= 18.5 (mA) with a current error of ±12%.
2
.
F
LED and the output voltage V
8
FP
F
(mA) does not flow to the LED.
LED is obtained as the mean current.
Figure 4 Application Circuit
GND
Note
A
S-Di
K
F
LED exceeds P
IZD
R_sens
O
0.47 µF
R_ZD
2.7 Ω
TB62732FUG
. The mean output
C2
o
= 320 (mW), it
2006-06-14
IF