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参数资料
| 型号： | LM1972MNOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 消费家电 |
| 英文描述： | SPECIALTY CONSUMER CIRCUIT, PDSO20 |
| 封装： | SOP-20 |
| 文件页数： | 9/12页 |
| 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
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LM1972
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM1972MX | 功能描述:衰减器 -IC RoHS:否 制造商:Skyworks Solutions, Inc. 最大衰减:18 dB 容差: 阻抗: 功率额定值:30 dBm 安装风格:SMD/SMT 工作温度范围:- 40 C to + 85 C |
| LM1972MX/NOPB | 功能描述:有源衰减器 RoHS:否 制造商:TriQuint Semiconductor 通道数量: 最大频率: 阻抗: 最大 VSWR: 位数: 最大工作温度: 最小工作温度: |
| LM1972N | 功能描述:IC AUDIO ATTENUATOR 2CH 20-DIP RoHS:否 类别:集成电路 (IC) >> 线性 - 音频处理 系列:- 其它有关文件:STA321 View All Specifications 标准包装:1 系列:Sound Terminal™ 类型:音频处理器 应用:数字音频 安装类型:表面贴装 封装/外壳:64-LQFP 裸露焊盘 供应商设备封装:64-LQFP EP（10x10） 包装:Digi-Reel® 其它名称: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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