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參數(shù)資料
| 型號： | SM8120 |
| 廠商： | Seiko NPC Corporation |
| 元件分類： | LED驅(qū)動器 |
| 英文描述： | White LED Driver IC |
| 中文描述： | 白光LED驅(qū)動IC |
| 文件頁數(shù)： | 5/14頁 |
| 文件大?。?/td> | 201K |
| 代理商： | SM8120 |
SM8120A
NIPPON PRECISION CIRCUITS INC.—5
Selecting the Inductor (L)
The recommended inductance for use with the SM8120A is 22μH. The inductor DC resistance affects the
power efficiency, therefore a low DC resistance inductor is recommended. Note also that the peak inductor cur-
rent I
peak
should not exceed the inductor maximum current rating. In pulsed current mode control, the peak
inductor current I
peak
is given by the following equation.
I
peak
= (V
IN
×
T
ON
) / L
For example, if the input voltage V
IN
is 3.6V, the inductance L is 22μH, and the SW-Tr ON time T
then the peak inductor current I
peak
is (3.6
×
1.2
×
10
) / (2.2
Selecting the Capacitors (C
IN
, C
OUT
)
ON
is 1.2
μ
s,
-6
×
10
-6
) = 0.2A = 200mA.
The recommended capacitances for use with the SM8120A are 4.7μF ceramic input capacitor C
tantalum output capacitor C
OUT
. The input capacitor ESR ratings affect the ripple voltage, therefore capacitors
with low ESR rating are recommended. When the output capacitor ESR ratings are too low, it affect the
response to the FB pin, therefore tantalum capacitors are recommended. The input capacitor should be
mounted close to the SM8120A IC. Note that the capacitor voltage ratings should be selected to provide suffi-
cient margin for the applied input and output voltages.
IN
and 1.0μF
For example, if a lithium-ion battery (2.5 to 4.5V) is connected to the input and 3 white LEDs connected in
series at the output draw 20mA, then the maximum input voltage is 4.5V and the maximum output voltage is
(4.0V
×
3 LEDs) + 0.5V = 12.5V. Therefore, the input capacitor should have a voltage rating of 6V, and the
output capacitor should have a voltage rating of 16V.
Selecting the Rectifier Schottky Barrier Diode (SBD)
The rectifier schottky barrier diode forward-direction voltage drop affects the power efficiency, therefore a
Schottky barrier diode with low forward-direction voltage drop is recommended. Note that the diode should be
selected to provide sufficient margin for the rated current and reverse-direction withstand voltage.
Board Layout Notes
The following precautions should be followed for stable device operation.
I
The inductor L and Schottky barrier diode SBD should be connected close to the pin SW using thick, short
circuit wiring.
The input capacitor C
IN
should be mounted close to the IC.
The IC supply voltage V
DD
wiring and inductor supply wiring should be isolated, reducing any common
impedances.
The ground wiring should be connected at a single point, reducing any common impedances.
I
I
I
SW
FB
L
C
IN
V
IN
SBD
C
OUT
R1
VDD
CE
VSS
LED
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SM8120A | White LED Driver IC |
| SM8120AH | White LED Driver IC |
| SM8143 | EL Sheet Driver |
| SM8143A | EL Sheet Driver |
| SM8143AV | EL Sheet Driver |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SM8120A | 制造商:NPC 制造商全稱:Nippon Precision Circuits Inc 功能描述:White LED Driver IC |
| SM8120AH | 制造商:NPC 制造商全稱:Nippon Precision Circuits Inc 功能描述:White LED Driver IC |
| SM8121A | 制造商:NPC 制造商全稱:Nippon Precision Circuits Inc 功能描述:White LED Driver IC |
| SM8121AD | 制造商:NPC 制造商全稱:Nippon Precision Circuits Inc 功能描述:White LED Driver IC |
| SM8121AH | 制造商:NPC 制造商全稱:Nippon Precision Circuits Inc 功能描述:White LED Driver IC |
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