- 您现在的位置：买卖IC网 > PDF目录224108 > LMV1026URX (NATIONAL SEMICONDUCTOR CORP) PDM Output with Pre-Amplifier for Electret Microphones PDF资料下载
参数资料
| 型号： | LMV1026URX |
| 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： | 4/18页 |
| 文件大小： | 560K |
| 代理商： | LMV1026URX |
A-WEIGHTED FILTER
The human ear has a frequency range from about 20 Hz to
20 kHz. Within this range the sensitivity of the human ear is
not equal for each frequency. In order to approach a natural
hearing response, weighting filters are introduced. One of
these filters is the A-weighted filter. The A-weighted filter is
commonly used in signal-to-noise ratio measurements, where
sound is compared to device noise. The filter improves the
correlation of the measured data to the signal-to-noise ratio
perceived by the human ear.
20133440
FIGURE 4. A-weighted Filter
SENSITIVITY
Sensitivity is a measure for the transfer from the applied
acoustic signal to the output of the microphone. Conventional
JFET microphones and microphones with built-in gain have
a sensitivity that is expressed in dB(V/Pa), where 0dB = 1V/
Pa. A certain pressure on the electret of the microphone gives
a certain voltage at the output of the microphone. Since the
LMV1024 microphone has a digital output, the sensitivity will
be stated in dB(Full Scale/Pascal) or dB(FS/Pa) as opposed
to conventional microphones. This section compares the var-
ious microphone types and their sensitivity. Examples are
given to calculate the resulting output for a given sound pres-
sure.
Sound Pressure Level
The volume of sound applied to a microphone is usually stat-
ed as a sound pressure in dB SPL. This unity of dB SPL refers
to the threshold of hearing of the human ear. The sound pres-
sure in decibels is defined by:
SPL = 20 log (P
M/PO)
Where,SPL is the Sound Pressure in dB SPLP
M is the mea-
sured absolute sound pressure in PaP
O is the threshold of
hearing (20 Pa)
In order to calculate the resulting output voltage of the electret
element for a given sound pressure in dB SPL, the absolute
sound pressure P
M must be known. This is the absolute sound
pressure in decibels referred to 1 Pa instead of 20 Pa.
The absolute sound pressure P
M in dBPa is given by:PM =
SPL (dB SPL) + P
O (dBPa)PM = SPL + 20*log 20 PaPM =
SPL - 94 dB
JFET Microphone
Translation from the absolute sound pressure level to a volt-
age can be done when the electrets sensitivity is known. A
typical electret element has a sensitivity of 44 dB(V/Pa). This
is also the typical sensitivity number for the JFET microphone,
since a JFET usually has a gain of about 1x (0 dB). A block
diagram of a microphone with a JFET is given in Figure 5.
Example: Busy traffic has a Sound Pressure of 70 dB SPL.
Microphone Output = SPL + C + S
Where,SPL is the Sound Pressure in dB SPLC is the dB SPL
to dBPa conversion (94 dB)S is the Sensitivity in dB(V/Pa)
Microphone Output = 70 – 94 – 44 = 68 dBVThis is equiva-
lent to 1.13 mV
PP.
The analog output signal is so low that it can easily be dis-
torted by interference from outside the microphone. Addition-
al gain is desirable to make the signal less sensitive to
interference.
www.national.com
12
201334 Version 3 Revision 4
Print Date/Time: 2009/07/20 17:12:49
LMV1024/LMV1026
相关PDF资料 |
PDF描述 |
|---|---|
| LNG308GKG | T-1 SINGLE COLOR LED, GREEN, 3 mm |
| LOM67K-J2L1-24 | SINGLE COLOR LED, ORANGE, 1.5 mm |
| LP-XX-FREQ-1-XXP | CRO, 800 MHz - 2200 MHz |
| LP1OA1AG | PUSHBUTTON SWITCH, SPST, MOMENTARY, 0.1A, 30VDC, PANEL MOUNT |
| LP2988AILD-5 | Micropower, 200 mA Ultra Low-Dropout Voltage Regulator with Programmable Power-On Reset Delay; Low Noise Version Available (LP2988) |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LMV1026URX/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) |
| LMV102M5 | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| LMV102M5X | 功能描述:IC AMPLIFIER FIXED-GAIN SOT23-5 RoHS:是 类别:集成电路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 标准包装:1,000 系列:- 放大器类型:电压反馈 电路数:4 输出类型:满摆幅 转换速率:33 V/µs 增益带宽积:20MHz -3db带宽:30MHz 电流 - 输入偏压:2nA 电压 - 输入偏移:3000µV 电流 - 电源:2.5mA 电流 - 输出 / 通道:30mA 电压 - 电源，单路/双路(±):4.5 V ~ 16.5 V，±2.25 V ~ 8.25 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:14-SOIC（0.154"，3.90mm 宽） 供应商设备封装:14-SOIC 包装:带卷 (TR) |
| LMV102M7 | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| LMV102M7X | 功能描述:IC AMP FIXED GAIN SC-70-5 RoHS:是 类别:集成电路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 标准包装:1,000 系列:- 放大器类型:电压反馈 电路数:4 输出类型:满摆幅 转换速率:33 V/µs 增益带宽积:20MHz -3db带宽:30MHz 电流 - 输入偏压:2nA 电压 - 输入偏移:3000µV 电流 - 电源:2.5mA 电流 - 输出 / 通道:30mA 电压 - 电源，单路/双路(±):4.5 V ~ 16.5 V，±2.25 V ~ 8.25 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:14-SOIC（0.154"，3.90mm 宽） 供应商设备封装:14-SOIC 包装:带卷 (TR) |
发布紧急采购，3分钟左右您将得到回复。