TB62731FUG 查看數據表（PDF） - Marktech Optoelectronics

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TB62731FUG

Step-up DC-DC Converter for White LED Driver

Marktech Optoelectronics 

TB62731FUG

Selection of R_sens

Resistance between pin K and GND R_sens (Ω) is used for setting output current Io. The mean output current Io

can be set according to the resistance.

The mean current Io (mA) to be set is roughly calculated as follows:

Io (mA) = 36 (mV) ÷ R_sens (Ω)

For example, when R_sens = 1.8 (Ω), Io = 20 (mA).

Take a current error of ±10% (not including R_sens error) into consideration.

The IC has a minimum output Po = 320 (mA, choke coil = 47 µH).

At that time, if the product of mean current Io and output voltage Vo exceeds Po = 320 (mW), mean current Io

may become less than the desired value.

If the IC is not connected to the output-side capacitor (for smoothing), the set current Io can be obtained.

At that time, because the current flowing to the LED is a pulse current with a maximum peak value of 270 mA,

make sure that surge current IFP (mA) does not flow to the LED.

Toshiba recommend use of components with low reactance (parasitic inductance) and minimized PCB wiring.

Toshiba also recommend allocating components in the application circuit diagram as near each other as possible.

Relation between set current IO and setting resistance R_sens

(typical value: VCC = 3.6 V, Ta = 25°C)

40

: Io (mA)

30

20

10

0

10 9.1 8.2 6.8 5.6 4.7

3.3 2.7 2.2 2 1.8 1.5 1.2 1

Resistance for setting current R_sens (Ω)

Figure 4

9

2004-09-14

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