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参数资料
| 型号： | LMV1024URX |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 音频／视频放大 |
| 英文描述： | PDM Output with Pre-Amplifier for Electret Microphones |
| 中文描述： | 2 CHANNEL, AUDIO AMPLIFIER, PBGA6 |
| 封装： | 0.35 MM, LEAD FREE, MICRO SMD-6 |
| 文件页数： | 6/18页 |
| 文件大小： | 560K |
| 代理商： | LMV1024URX |
(2)
Or in decibels:Digital Output (dBFS) = Input (dBV) - Refer-
ence (dB) + A
Where,Input = 20 Log V
INPUT (VRMS)Ref = 20 Log VREF
(V
RMS)A is the Gain (dB)
For the LMV1024/LMV1026 the reference voltage V
REF is
1.5V
P (1.06 VRMS) and the Gain A is 15.7 dB. These param-
eters are fixed inside the device. Knowing this, Equation 2 can
be simplified:
Digital Output (dBFS) = V
INPUT (dBV) - 0.5 + 15.7Digital Out-
put (dBFS) = V
INPUT (dBV) + 15.2
The sensitivity of the digital microphone is the sensitivity of a
conventional microphone plus the input to output transfer of
the LMV1024. The sensitivity of a typical digital microphone
is therefore: 44 + 15.2 = 28.8 dB(FS/Pa).
Digital Output = SP + C + S
Where,SP is the Sound Pressure in dB SPLC is the dB SPL
to dBPa conversion (94 dB)S is the Sensitivity in dB(V/Pa)
Taking the example of busy traffic (70 dB SPL) again results
in the following digital output (dBFS):
Digital Output (dBFS) = SP - C + SDigital Output (dBFS) = 70
- 94 - 28.8 = 52.8 dBFS
ANALOG-TO-DIGITAL CONVERTER
The ADC used in the LMV1024/LMV1026 is an one bit sigma
delta converter with a Pulse Density Modulated output signal
(PDM). The output of this ADC can be either High (one) or
Low (zero). Assume that the LMV1024/LMV1026 input is at
the minimum level. In that case the DATA output will produce
almost only “zeros”. When the input increases, the amount of
“ones” increases too. At mid-point, where the input is 0V, the
number of “zeros” will equal the number of “ones”. At the time
that the input approaches the maximum level, the DATA out-
put produces a majority of “ones”. Figure 6 shows the result-
ing DATA output as function of the input.
20133472
FIGURE 6. DATA Output versus Input Amplitude
An important characteristic of the sigma delta converter is that
the noise is shifted out of the band to frequencies above the
band of interest. The band that can be used (Audio Band-
width) relates directly the applied clock frequency. Table 1
shows the relation between the Clock Frequency and a cou-
ple of common Audio Bandwidths.
TABLE 1. Audio Bandwidth vs. Clock Frequency
Clock Frequency
Audio Bandwidth
408 kHz
3.4 kHz
960 kHz
8 kHz
1.2 MHz
10 kHz
1.92 MHz
16 kHz
2.4 MHz
20 kHz
The high corner of the band of interest (knee) is determined
by the clock frequency divided by 2 times the OSR. The factor
of two comes from the Nyquist theorem. The over sampling
ratio (OSR) of this particular ADC is chosen at 60. This sets
the high corner of the band at the clock frequency divided by
120. For instance when a bandwidth of 10 kHz is desired, the
clock frequency needs to be 1.2 MHz or higher. Figure 7 de-
picts the noise shaping effect in a frequency spectrum plot,
where a 1 kHz signal is applied.
20133461
FIGURE 7. Frequency Spectrum
www.national.com
14
201334 Version 3 Revision 4
Print Date/Time: 2009/07/20 17:12:49
LMV1024/LMV1026
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LMV1024URX/NOPB | 功能描述:IC PRE AMP MIC MONO AB ADC 6USMD RoHS:是 类别:集成电路 (IC) >> 线性 - 音頻放大器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:DirectDrive® 类型:H 类 输出类型:耳机，2-通道（立体声） 在某负载时最大输出功率 x 通道数量:35mW x 2 @ 16 欧姆 电源电压:1.62 V ~ 1.98 V 特点:I²C，麦克风，静音，短路保护，音量控制 安装类型:表面贴装 供应商设备封装:25-WLP（2.09x2.09） 封装/外壳:25-WFBGA，WLCSP 包装:带卷 (TR) |
| LMV1026 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:PDM Output with Pre-Amplifier for Electret Microphones |
| LMV1026UR | 制造商:NSC 制造商全称:National Semiconductor 功能描述:PDM Output with Pre-Amplifier for Electret Microphones |
| LMV1026UR/NOPB | 功能描述:IC PRE AMP MIC MONO AB ADC 6USMD RoHS:是 类别:集成电路 (IC) >> 线性 - 音頻放大器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:DirectDrive® 类型:H 类 输出类型:耳机，2-通道（立体声） 在某负载时最大输出功率 x 通道数量:35mW x 2 @ 16 欧姆 电源电压:1.62 V ~ 1.98 V 特点:I²C，麦克风，静音，短路保护，音量控制 安装类型:表面贴装 供应商设备封装:25-WLP（2.09x2.09） 封装/外壳:25-WFBGA，WLCSP 包装:带卷 (TR) |
| LMV1026URX | 制造商:NSC 制造商全称:National Semiconductor 功能描述:PDM Output with Pre-Amplifier for Electret Microphones |
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