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參數(shù)資料
| 型號(hào)： | LM4845ITL |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | Output Capacitor-less Audio Subsystem with Programmable National 3D |
| 中文描述： | 0.5 W, 2 CHANNEL, AUDIO AMPLIFIER, PBGA25 |
| 封裝： | MICRO, SMD-25 |
| 文件頁(yè)數(shù)： | 24/29頁(yè) |
| 文件大?。?/td> | 1392K |
| 代理商： | LM4845ITL |
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Application Information
(Continued)
NATIONAL 3D ENHANCEMENT
The LM4845 features a stereo headphone, 3D audio en-
hancement effect that widens the perceived soundstage
from a stereo audio signal. The 3D audio enhancement
creates a perceived spatial effect optimized for stereo head-
phone listening. The LM4845 has four discrete levels of 3D
effect that can be programmed: low, medium, high, and
maximum (Table 2), each level with an ever “widening” aural
effect, respectively.
The external capacitors, shown in Figure 6, are required to
enable the 3D effect. The value of the capacitors set the
cutoff frequency of the 3D effect, as shown by Equations 1
and 2. Note that the internal 20k
resistor is nominal
(
±
25%).
f
3DL(-3dB)
= 1 / 2
π
* 20k
* C
3DL
(1)
f
3DR(-3dB)
= 1 / 2
π
* 20k
* C
3DR
(2)
Optional resistors R
and R
can also be added (Figure
7) to affect the -3dB frequency and 3D magnitude.
f
3DL(-3dB)
= 1 / 2
π
* (20k
+ R
3DL
) * C
3DL
(3)
f
3DR(-3dB)
= 1 / 2
π
* 20k
+ R
3DR
) * C
3DR
(4)
AV (change in AC gain) = 1 / 1 + M, where M represents
some ratio of the nominal internal resistor, 20k
(see ex-
ample below).
f
3dB
(3D) = 1 / 2
π
(1 + M)(20k
* C
3D
)
(5)
C
Equivalent
(new) = C
3D
/ 1 + M
(6)
TABLE 6. Pole Locations
R
3D
(k
)
(optional)
C
3D
(nF)
M
AV (dB)
f-3dB (3D)
(Hz)
Value of C
3D
to keep same
pole location
(nF)
new Pole
Location
(Hz)
0
1
5
10
20
68
68
68
68
68
0
0
117
111
94
78
59
0.05
0.25
0.50
1.00
–0.4
–1.9
–3.5
–6.0
64.8
54.4
45.3
34.0
117
117
117
117
PCB LAYOUT AND SUPPLY REGULATION
CONSIDERATIONS FOR DRIVING 8
LOAD
Power dissipated by a load is a function of the voltage swing
across the load and the load’s impedance. As load imped-
ance decreases, load dissipation becomes increasingly de-
pendent on the interconnect (PCB trace and wire) resistance
between the amplifier output pins and the load’s connec-
tions. Residual trace resistance causes a voltage drop,
which results in power dissipated in the trace and not in the
load as desired. For example, 0.1
trace resistance reduces
the output power dissipated by an 8
load from 158.3mW to
156.4mW. The problem of decreased load dissipation is
exacerbated as load impedance decreases. Therefore, to
maintain the highest load dissipation and widest output volt-
age swing, PCB traces that connect the output pins to a load
must be as wide as possible.
Poor power supply regulation adversely affects maximum
output power. A poorly regulated supply’s output voltage
decreases with increasing load current. Reduced supply
voltage causes decreased headroom, output signal clipping,
and reduced output power. Even with tightly regulated sup-
plies, trace resistance creates the same effects as poor
supply regulation. Therefore, making the power supply
traces as wide as possible helps maintain full output voltage
swing.
20105995
FIGURE 6. External 3D Effect Capacitors
20105994
FIGURE 7. External RC Network with Optional R
3DL
and R
3DR
Resistors
L
www.national.com
24
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4845ITL/NOPB | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LM4845ITLX/NOPB | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LM4846 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Output Capacitor-less Audio Subsystem with Programmable National 3D |
| LM4846TL | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Output Capacitor-less Audio Subsystem with Programmable National 3D |
| LM4846TL/NOPB | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
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