Datasheet

Datasheet

21/34

TSZ02201-0F1F0C100240-1-2

© 2013 ROHM Co., Ltd. All rights reserved.

15.Feb.2016 Rev.006

www.rohm.com

TSZ22111・15・001

BD9486F

3.3.2. Inductor Selection

The inductor value affects the input ripple current. As shown in section 3.3.1,

Where

L: coil inductance [H]

In continuous current mode, ⊿IL is set to 30% to 50% of the output load current in many cases.

In using smaller inductor, the boost is operated by the discontinuous current mode in which the coil current returns to

zero at every period.

*The current exceeding the rated current value of inductor flown through the coil causes magnetic saturation, results in

decreasing in efficiency. Inductor needs to be selected to have such adequate margin that peak current does not

exceed the rated current value of the inductor.

*To reduce inductor loss and improve efficiency, inductor with low resistance components (DCR, ACR) needs to be

selected

3.3.3. Output Capacitance Cout Selection

Output capacitor needs to be selected in consideration of equivalent series resistance

required to even the stable area of output voltage or ripple voltage. Be aware that set

LED current may not be flown due to decrease in LED terminal voltage if output ripple

component is high.

(4)

]

V

[

R

IL

Vout

ESR

　・・・・・　　

　

Δ

Δ





When the coil current is charged to the output capacitor as MOS turns off, much output

ripple is caused. Much ripple voltage of the output capacitor may cause the LED current

ripple.

* Rating of capacitor needs to be selected to have adequate margin against output voltage.

*To use an electrolytic capacitor, adequate margin against allowable current is also necessary. Be aware that the LED

current is larger than the set value transitionally in case that LED is provided with PWM dimming especially.

3.3.4. MOSFET Selection

There is no problem if the absolute maximum rating is larger than the rated current of the inductor L, or is larger than

charge) needs to be selected to achieve high-speed switching.

* One with over current protection setting or higher is recommended.

* The selection of one with small on resistance results in high efficiency.

3.3.5. Rectifying Diode Selection

A schottky barrier diode which has current ability higher than the rated current of L, reverse voltage larger than the

]

A

[

]

Hz

[

f

]

V

[

V

]

H

[

L

]

V

[

V

])

V

[

V

]

V

[

V

(

IL

SW

OUT

IN

IN

OUT











Δ

]

A

[

]

A

[

IL

]

A

[

I

Ipeak

IN

2







]

A

[

[%]

]

V

[

V

]

A

[

I

]

V

[

V

I

IN

OUT

OUT

IN









Figure 29. Inductor current waveform and diagram

Figure 30. Output capacitor diagram

V

OUT

V

IN

C

OUT

R

CS

L

R

ESR

I

L