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參數資料
| 型號： | LM1972MNOPB |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 消費家電 |
| 英文描述： | SPECIALTY CONSUMER CIRCUIT, PDSO20 |
| 封裝： | SOP-20 |
| 文件頁數： | 9/12頁 |
| 文件大小： | 406K |
| 代理商： | LM1972MNOPB |
Application Information
ATTENUATION STEP SCHEME
The fundamental attenuation step scheme for the LM1972
μPot is shown in Figure 3. This attenuation step scheme,
however, can be changed through programming techniques
to fit different application requirements. One such example
would be a constant logarithmic attenuation scheme of 1dB
steps for a panning function as shown in Figure 4. The only
restriction to the customization of attenuation schemes are
the given attenuation levels and their corresponding data bits
shown in Table 1. The device will change attenuation levels
only when a channel address is recognized. When recog-
nized, the attenuation level will be changed corresponding to
LM1972 can be configured as a panning control which sepa-
rates the mono signal into left and right channels. This circuit
may utilize the fundamental attenuation scheme of the
LM1972 or be programmed to provide a constant 1dB loga-
rithmic attenuation scheme as shown in Figure 4.
LM1972 Channel Attenuation
vs Digital Step Value
1197806
FIGURE 3. LM1972 Attenuation Step Scheme
LM1972 Channel Attenuation
vs Digital Step Value
(Programmed 1.0dB Steps)
1197807
FIGURE 4. LM1972 1.0dB
Attenuation Step Scheme
LM1972 Channel Attenuation
vs Digital Step Value
(Programmed 2.0dB Steps)
1197808
FIGURE 5. LM1972 2.0dB Attenuation Step Scheme
1197809
FIGURE 6. Mono Panning Circuit
INPUT IMPEDANCE
The input impedance of a
μPot is constant at a nominal
40 k
Ω. To eliminate any unwanted DC components from
propagating through the device it is common to use 1
μF input
coupling caps. This is not necessary, however, if the dc offset
from the previous stage is negligible. For higher performance
systems, input coupling caps are preferred.
OUTPUT IMPEDANCE
The output of a
μPot varies typically between 25 kΩ and
35 k
Ω and changes nonlinearly with step changes. Since a
μPot is made up of a resistor ladder network with a logarithmic
attenuation, the output impedance is nonlinear. Due to this
configuration, a
μPot cannot be considered as a linear poten-
tiometer, but can be considered only as a logarithmic attenu-
ator.
It should be noted that the linearity of a
μPot cannot be mea-
sured directly without a buffer because the input impedance
of most measurement systems is not high enough to provide
the required accuracy. Due to the low impedance of the mea-
surement system, the output of the
μPot would be loaded
down and an incorrect reading will result. To prevent loading
from occurring, a JFET input op amp should be used as the
buffer/amplifier. The performance of a
μPot is limited only by
the performance of the external buffer/amplifier.
www.national.com
6
LM1972
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LM1972MX | 功能描述:衰減器 -IC RoHS:否 制造商:Skyworks Solutions, Inc. 最大衰減:18 dB 容差: 阻抗: 功率額定值:30 dBm 安裝風格:SMD/SMT 工作溫度范圍:- 40 C to + 85 C |
| LM1972MX/NOPB | 功能描述:有源衰減器 RoHS:否 制造商:TriQuint Semiconductor 通道數量: 最大頻率: 阻抗: 最大 VSWR: 位數: 最大工作溫度: 最小工作溫度: |
| LM1972N | 功能描述:IC AUDIO ATTENUATOR 2CH 20-DIP RoHS:否 類別:集成電路 (IC) >> 線性 - 音頻處理 系列:- 其它有關文件:STA321 View All Specifications 標準包裝:1 系列:Sound Terminal™ 類型:音頻處理器 應用:數字音頻 安裝類型:表面貼裝 封裝/外殼:64-LQFP 裸露焊盤 供應商設備封裝:64-LQFP EP（10x10） 包裝:Digi-Reel® 其它名稱:497-11050-6 |
| LM1972N | 制造商:Texas Instruments 功能描述:AUDIO ATTENUATOR 78DB 1972 DIP20 |
| LM1972N/NOPB | 制造商:Texas Instruments 功能描述:Digital Attenuator 104dB Attenuation 20-Pin PDIP Rail |
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