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參數(shù)資料
| 型號： | HV857 |
| 廠商： | ELAN Microelctronics Corp . |
| 英文描述： | High Voltage EL Lamp Driver for Low Noise Applications(高電壓,低噪雙路EL燈驅(qū)動器) |
| 中文描述： | 高壓發(fā)光燈驅(qū)動器的低噪聲的應用（高電壓，低噪雙路發(fā)光燈驅(qū)動器） |
| 文件頁數(shù)： | 8/14頁 |
| 文件大小： | 638K |
| 代理商： | HV857 |
8
HV857 Application Note
Mobile Phone Circuit for Audible Noise Reduction:
1
The following table provides EL lamp audible noise and brightness for circuits which were designed based on typical EL lamp sizes for
Mobile phone applications. See Figure 1, Table 3.
t
c
r
C
+
e
R
z
S
s
p
e
e
m
S
a
L
e
u
s
N
A
e
s
s
e
n
t
h
g
B
p
m
a
L
e
g
a
V
y
p
u
S
y
p
n
e
u
S
r
u
x
C
L
t
p
n
m
e
u
a
q
L
e
y
c
r
F
m
l
m
/
C
2
V
D
D
V
N
I
1
n
2
K
0
+
A
B
d
1
3
9
0
7
2
V
0
V
0
A
m
6
2
z
H
0
5
2
n
2
K
5
2
+
A
B
d
0
3
3
9
7
2
A
m
3
2
n
2
K
0
5
+
A
B
d
2
2
0
0
1
1
A
m
5
2
n
2
K
5
7
+
A
B
d
7
2
3
8
1
1
A
m
6
2
n
2
K
0
0
1
+
A
B
d
3
2
0
8
6
5
A
m
3
2
2
n
2
K
0
+
A
B
d
0
3
0
9
9
5
2
V
0
V
0
A
m
4
1
z
H
0
5
2
n
7
2
K
5
2
+
A
B
d
3
2
5
3
3
7
2
A
m
5
1
n
2
K
0
5
+
A
B
d
0
2
2
7
5
5
1
A
m
6
1
n
2
K
5
7
+
A
B
d
4
2
5
8
0
6
1
A
m
9
1
n
2
K
5
9
+
A
B
d
9
2
0
2
5
3
1
A
m
5
1
n
2
K
0
2
1
+
A
B
d
0
2
2
4
9
6
1
A
m
6
1
How to Minimize EL Lamp
Audible Noise:
The EL lamp, when lit, generates an audible noise. This is due
to EL lamp construction which creates a major problem for
applications where the EL lamp can be close to the ear such as
cellular phones. The noisiest waveform is a square wave and the
quietest waveform has been assumed to be a sine wave.
After extensive research, Supertex has developed a waveform
that is quieter than a sine wave. The waveform takes the shape
of approximately 2RC time constants for rising and 2RC time
constants for falling, where the C is the capacitance of the lamp
and R is the external resistor used in series with one side of the
lamp. This waveform has been proven to generate less noise
than a sine wave.
The audible noise from the EL lamp can be set at a desired level
based on the series resistor value used with the lamp. We have
chosen two commonly used lamp sizes for the mobile phones to
demonstrate the effect of series resistor on the audible noise
generated by the EL lamp. It is important to note that use of this
resistor will reduce the voltage across the lamp. Reduction of
voltage across the lamp will also has another effect on the overall
performance of the Supertex EL drivers, age compensation
(patent pending). This addresses a very important issue. EL
lamp life is an important design concern to mobile phone
manufacturers.
As an EL lamp ages, its brightness is reduced and its capacitance
is diminished. By using the RC model to reduce the audible noise
generated by an EL lamp, the voltage across the lamp will
increase as its capacitance diminishes. Hence the increase in
voltage will compensate for the reduction of the brightness. As a
result, it will extend an EL lamp’s half-life (half the original
brightness).
Effect of Series Resistor on EL
Lamp Audible Noise and
Brightness:
Increasing the value of the series resistor with the lamp will
reduce the audible noise of an EL lamp as well as its brightness.
This is due to the fact that the output voltage across the lamp will
be reduced and the output waveform will have rounder edges.
Note: 1. All values are nominal.
Table 1
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相關(guān)代理商/技術(shù)參數(shù) |
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| HV857_07 | 制造商:SUPERTEX 制造商全稱:SUPERTEX 功能描述:Low Noise, High Voltage EL Lamp Driver IC |
| HV857DB1 | 功能描述:電源管理IC開發(fā)工具 HV857 Demo Board RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| HV857K7-G | 功能描述:顯示驅(qū)動器和控制器 High Voltage Low Noise EL Lamp RoHS:否 制造商:Panasonic Electronic Components 工作電源電壓:2.7 V to 5.5 V 最大工作溫度: 安裝風格:SMD/SMT 封裝 / 箱體:QFN-44 封裝:Reel |
| HV857L | 制造商:SUPERTEX 制造商全稱:SUPERTEX 功能描述:Low Noise, High Voltage EL Lamp Driver IC |
| HV857LDB1 | 功能描述:電源管理IC開發(fā)工具 HIGH VOLTAGE LOW NOISE EL LAMP DRIVER DEMOBOARD RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
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