- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄385487 > LM4918LQ (NATIONAL SEMICONDUCTOR CORP) Stereo Audio Amp with AGC Control PDF資料下載
參數(shù)資料
| 型號(hào)： | LM4918LQ |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻控制 |
| 英文描述： | Stereo Audio Amp with AGC Control |
| 中文描述： | 2 CHANNEL(S), VOLUME CONTROL CIRCUIT, QCC32 |
| 封裝： | LLP-32 |
| 文件頁數(shù)： | 12/17頁 |
| 文件大?。?/td> | 646K |
| 代理商： | LM4918LQ |
Application Information
(Continued)
AUTOMATIC GAIN CONTROL (AGC)
The AGC represents a closed loop gain control network in
conjunction with the peak detect monitoring the outputs of
the power amplifier section. A reference voltage is put on the
“AGC Ref In” pin to set the desired dynamic range of the
AGC. This voltage should be set to allow for maximum
desired output level for the expected range of the input
signal. The AGC may provide anywhere from 0 to 24dB of
attenuation. The peak detect constantly updates the AGC
block with information about the maximum level of the output
signal. Internally, if this peak value is higher than the set
reference voltage, the AGC will reduce the gain of the circuit
until the output peak is lower than the reference voltage. This
entire process is timed by the Chold capacitor (in conjunction
with Rdischarge), which determines the hold time between
peaks while restoring gain (gain returns to normal levels
after being attenuated by large power amp output signal).
The circuit shown in Figure 3 best describes the AGC loop
operation. Square nodes are external pins. Vbp is the by-
pass voltage. As is shown below, the peak detect section
(PD) monitors all outputs of the power amp (VoL+, VoL-,
VoR+, and VoR-). Peaks are fed into the peak buffer, regu-
lated by Chold and Rdis. The output of the peak buffer
(VpkBfr) is then compared to VagcRef. The AGC amplifier
then sets the ADC output to control the gain setting in 32
discrete steps from 0 to –24dB. Gain will remain reduced
until peak levels (Vpkbfr) return below the VagcRef, as buff-
ered by the peak buffer and Chold. This means gain will
slowly increase (speed determined by Chold) back to normal
levels (maximum gain set) or until the peaks again exceed
the reference level.
The reference voltage VagcRef should be set in conjunction
with the gain settings on the power amplifier stage to provide
maximum gain (0dB) for the typical desired maximum output
level of the part for a maximum input level. This will ensure
that both the full 24dB dynamic range of the AGC is used
effectively and that maximum effective audio levels may be
reached without clipping. Typical AGC peak gain values for
given VagcRef voltages are shown in Table 1. These are
taken with a 20M
pullup resistor on Chold (as used shown
on the demo board). These are shown as typical values only
– VagcRef level should be set with the factors described
above.
200913E7
FIGURE 3. Block Diagram with external component for AGC closed loop
L
www.national.com
12
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM4924 | 2 Cell Battery, 40mW Per Channel Output Capacitor-Less(OCL) Stereo Headphone Audio Amplifier |
| LM4924MM | 2 Cell Battery, 40mW Per Channel Output Capacitor-Less(OCL) Stereo Headphone Audio Amplifier |
| LM4924SD | 2 Cell Battery, 40mW Per Channel Output Capacitor-Less(OCL) Stereo Headphone Audio Amplifier |
| LM4929 | Stereo 40mW Low Noise Headphone Amplifier with OCL Output |
| LM4929MM | Stereo 40mW Low Noise Headphone Amplifier with OCL Output |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4918LQ/NOPB | 功能描述:IC AMP AUDIO PWR 1.1W STER 32LLP RoHS:是 類別:集成電路 (IC) >> 線性 - 音頻放大器 系列:Boomer® 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:2,500 系列:DirectDrive® 類型:H 類 輸出類型:耳機(jī)，2-通道（立體聲） 在某負(fù)載時(shí)最大輸出功率 x 通道數(shù)量:35mW x 2 @ 16 歐姆 電源電壓:1.62 V ~ 1.98 V 特點(diǎn):I²C，麥克風(fēng)，靜音，短路保護(hù)，音量控制 安裝類型:表面貼裝 供應(yīng)商設(shè)備封裝:25-WLP（2.09x2.09） 封裝/外殼:25-WFBGA，WLCSP 包裝:帶卷 (TR) |
| LM4919 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:1.5V, Mono 85mW BTL Output, 14mW Stereo Headphone Audio Amplifier |
| LM4919A WAF | 制造商:Texas Instruments 功能描述: |
| LM4919MM | 制造商:Texas Instruments 功能描述:AMP STEREO H/P 1.5V 14MW SMD 4919 |
| LM4919MM/NOPB | 功能描述:IC AMP AUDIO MONO/STER AB 10MSOP RoHS:是 類別:集成電路 (IC) >> 線性 - 音頻放大器 系列:Boomer® 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:2,500 系列:DirectDrive® 類型:H 類 輸出類型:耳機(jī)，2-通道（立體聲） 在某負(fù)載時(shí)最大輸出功率 x 通道數(shù)量:35mW x 2 @ 16 歐姆 電源電壓:1.62 V ~ 1.98 V 特點(diǎn):I²C，麥克風(fēng)，靜音，短路保護(hù)，音量控制 安裝類型:表面貼裝 供應(yīng)商設(shè)備封裝:25-WLP（2.09x2.09） 封裝/外殼:25-WFBGA，WLCSP 包裝:帶卷 (TR) |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。