參數(shù)資料
型號(hào)： SM8120
廠商： Seiko NPC Corporation
元件分類(lèi)： LED驅(qū)動(dòng)器
英文描述： White LED Driver IC
中文描述： 白光LED驅(qū)動(dòng)IC
文件頁(yè)數(shù)： 7/14頁(yè)
文件大?。?/td> 201K
代理商： SM8120
SM8120A
NIPPON PRECISION CIRCUITS INC.—7
BRIGHTNESS ADJUSTMENT
Brightness Adjustment using FB Pin
The LED brightness can be adjusted using an input DC control voltage connected through resistor R3 to the FB
pin. Alternatively, the brightness can be controlled by a PWM signal by adding a low-pass filter comprising
resistor R4 and capacitor C1. The PWM signal frequency range is determined by the low-pass filter coeffi-
cients. For example, the recommended values for resistor R4 (50k
) and capacitor C1 (0.1μF) provide a PWM
signal frequency range of 1kHz to 1MHz.
Brightness adjustment using FB pin (DC voltage input)
When the brightness is controlled by DC voltage (V
DC
) connected to resistor R3, the LED current (I
LED
) is
given by equation 1.
If the values R1 = 30
, R2 = 20k
, R3 = 100k
, V
FB
= 0.5V, and V
DC
= 0V are inserted in equation 1, the
LED current I
LED
= 20mA, as shown in equation 2.
If the values R1 = 30
, R2 = 20k
, R3 = 100k
, V
FB
= 0.5V, and V
DC
= 3V are inserted in equation 1, the
LED current I
LED
= 0mA, as shown in equation 3.
Taking the above diagram as an example, inserting the values R1 = 30
, R2 = 20k
, R3 = 100k
, V
FB
= 0.5V,
and V
DC
= 0 to 3V into equation 1 gives the maximum LED current I
LED
of 20mA when V
DC
= 0V (equation
2) and the minimum LED current I
LED
of 0mA when V
DC
= 3V (equation 3).
Brightness adjustment circuit using FB pin
(DC voltage input)
SW
VSS
FB
R1
30
SBD
D0 to 3V
1R3
R2
20k
VDD
CE
C
OUT
1.0
μ
F
L
22
μ
H
IN
C
μ
F
IN
V
LED
DC voltage vs. LED current
0
5
10
15
20
0.0
0.5
1.0
1.5
2.0
2.5
3.0
DC voltage [V]
L
R1
R2
× (
V
DC
V
FB
)
R3
I
LED
=
V
FB
... (1)
20,000
× (
0
0.5)
100,000
30
30
I
LED
=
=
=
0.5
0.6
20mA
... (2)
20,000
× (
3
0.5)
100,000
30
30
I
LED
=
=
=
0.5
0
0mA
... (3)
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參數(shù)描述
SM8120A 制造商:NPC 制造商全稱(chēng):Nippon Precision Circuits Inc 功能描述:White LED Driver IC
SM8120AH 制造商:NPC 制造商全稱(chēng):Nippon Precision Circuits Inc 功能描述:White LED Driver IC
SM8121A 制造商:NPC 制造商全稱(chēng):Nippon Precision Circuits Inc 功能描述:White LED Driver IC
SM8121AD 制造商:NPC 制造商全稱(chēng):Nippon Precision Circuits Inc 功能描述:White LED Driver IC
SM8121AH 制造商:NPC 制造商全稱(chēng):Nippon Precision Circuits Inc 功能描述:White LED Driver IC
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