參數(shù)資料
型號(hào)： SM8120
廠商： Seiko NPC Corporation
元件分類： 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)： 6/14頁(yè)
文件大?。?/td> 201K
代理商： SM8120
SM8120A
NIPPON PRECISION CIRCUITS INC.—6
LED OPEN-CIRCUIT PROTECTION
When there is no load (LED open-circuit), the FB pin is pulled-down and then switching occurs at maximum
frequency. Consequently, the output voltage continues to be boosted and the SW pin voltage may exceed the
maximum rating of 27V. A zener diode can be added so that it acts as the output load when the LED is open-
circuit, preventing the SW voltage from rising. The zener diode must be selected so that the zener does not
breakdown during normal operation. The zener voltage V
N is the number of LEDs connected in series, V
F MAX
V
OUT MAX
is the SW pin maximum output voltage, V
FB
rier diode forward-bias voltage drop.
ZD
is the maximum LED forward-bias voltage drop,
is the FB pin voltage, and V
range is given by the following relationship, where
SBD
is the Schottky-bar-
(V
F MAX
When the load is applied using a connector (SM8120A and LEDs on separate boards), the zener diode should
be mounted on the same board as the SM8120A device so that the SW boost prevention function can operate
when the load is disconnected.
×
N)
≤
V
ZD
≤
(V
OUT MAX
V
FB
V
SBD
)
Zener Diode (ZD) Only Connection
When the load is removed (LEDs open circuit), the output voltage is determined by the zener voltage, and the
output current is determined by the output current-setting resistance. Consequently, the output current when the
load is removed is not limited, and thus the input current cannot be controlled.
Zener Diode (ZD) and Current-Limiting Resistance Connection
When the load is removed (LEDs open circuit), the output voltage is determined by the zener voltage, and the
output current is determined by the sum of the output current-setting resistance and the current-limiting resis-
tance. Consequently, the output current is limited when the load is removed, and the input current can be con-
trolled.
VSS
FB
L
22
μ
H
C
IN
4.7
μ
F
V
3.6V
SBD
C
OUT
1.0
μ
F
LED Open
V
OUT
=V
ZD
+
0.5=15.5V
I
ZD
=0.5/33=15.15mA
33
ZD
(15V)
SW
VDD
CE
I
IN
=(V
OUT
I
ZD
)/V
IN
=65mA
SW
VSS
FB
L
22
μ
H
C
IN
4.7
μ
F
V
3.6V
SBD
C
OUT
1.0
μ
F
LED Open
V
OUT
=V
ZD
+
0.5=15.5V
I
ZD
=0.5/1033=0.48mA
33
ZD
(15V)
1k
VDD
CE
I
IN
=(V
OUT
I
ZD
)/V
IN
=2mA
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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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