- 您现在的位置：买卖IC网 > PDF目录10950 > ADAV801ASTZ (Analog Devices Inc)IC CODEC AUDIO R-DVD 3.3V 64LQFP PDF资料下载
参数资料
| 型号： | ADAV801ASTZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 8/60页 |
| 文件大小： | 0K |
| 描述： | IC CODEC AUDIO R-DVD 3.3V 64LQFP |
| 标准包装： | 1 |
| 类型： | 音频编解码器 |
| 数据接口： | 串行 |
| 分辨率（位）： | 24 b |
| ADC / DAC 数量： | 2 / 2 |
| 三角积分调变： | 无 |
| 动态范围，标准 ADC / DAC (db)： | 102 / 101 |
| 电压 - 电源，模拟： | 3 V ~ 3.6 V |
| 电压 - 电源，数字： | 3 V ~ 3.6 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 64-LQFP |
| 供应商设备封装： | 64-LQFP（10x10） |
| 包装： | 托盘 |
| 配用： | EVAL-ADAV801EBZ-ND - BOARD EVALUATION FOR ADAV801 |
第1页第2页第3页第4页第5页第6页第7页当前第8页第9页第10页第11页第12页第13页第14页第15页第16页第17页第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页第29页第30页第31页第32页第33页第34页第35页第36页第37页第38页第39页第40页第41页第42页第43页第44页第45页第46页第47页第48页第49页第50页第51页第52页第53页第54页第55页第56页第57页第58页第59页第60页
ADAV801
Rev. A | Page 16 of 60
Automatic Level Control (ALC)
The ADC record channel features a programmable automatic
level control block. This block monitors the level of the ADC
output signal and automatically reduces the gain, if the signal at
the input pins causes the ADC output to exceed a preset limit.
This function can be useful to maximize the signal dynamic
range when the input level is not well defined. The PGA can be
used to amplify the unknown signal, and the ALC reduces the
gain until the ADC output is within the preset limits. This
results in maximum front end gain.
Because the ALC block monitors the output of the ADC, the
volume control function should not be used. The ADC volume
control scales the results from the ADC, and any distortion
caused by the input signal exceeding the input range of the
ADC is still present at the output of the ADC, but scaled by a
value determined by the volume control register.
The ALC block has two functions, attack mode and recovery
mode. Recovery mode consists of three settings: no recovery,
normal recovery, and limited recovery. These modes are
discussed in the following sections. Figure 26 is a flow diagram
of the ALC block. When the ALC has been enabled, any
changes made to the PGA or ALC settings are ignored. To
change the functionality of the ALC, it must first be disabled.
The settings can then be changed and the ALC re-enabled.
Attack Mode
When the absolute value of the ADC output exceeds the level
set by the attack threshold bits in ALC Control Register 2, attack
mode is initiated. The PGA gain for both channels is reduced by
one step (0.5 dB). The ALC then waits for a time determined by
the attack timer bits before sampling the ADC output value
again. If the ADC output is still above the threshold, the PGA
gain is reduced by a further step. This procedure continues until
the ADC output is below the limit set by the attack threshold
bits. The initial gains of the PGAs are defined by the ADC left
PGA gain register and the ADC right PGA gain register, and
they can have different values. The ALC subtracts a common
gain offset to these values. The ALC preserves any gain differ-
ence in dB as defined by these registers. At no time do the PGA
gains exceed their initial values. The initial gain setting,
therefore, also serves as a maximum value.
The limit detection mode bit in ALC Control Register 1 deter-
mines how the ALC responds to an ADC output that exceeds
the set limits. If this bit is a 1, both channels must exceed the
threshold before the gain is reduced. This mode can be used to
prevent unnecessary gain reduction due to spurious noise on a
single channel. If the limit detection mode bit is a 0, the gain is
reduced when either channel exceeds the threshold.
No Recovery Mode
By default, there is no gain recovery. Once the gain has been
reduced, it is not recovered until the ALC is reset, either by
toggling the ALCEN bit in ALC Control Register 1 or by
writing any value to ALC Control Register 3. The latter option
is more efficient because it requires only one write operation to
reset the ALC function. No recovery mode prevents volume
modulation of the signal caused by adjusting the gain, which
can create undesirable artifacts in the signal. The gain can be
reduced but not recovered. Therefore, care should be taken that
spurious signals do not interfere with the input signal because
these might trigger a gain reduction unnecessarily.
Normal Recovery Mode
Normal recovery mode allows for the PGA gain to be recovered,
provided that the input signal meets certain criteria. First, the
ALC must not be in attack mode, that is, the PGA gain has been
reduced sufficiently such that the input signal is below the level
set by the attack threshold bits. Second, the output result from
the ADC must be below the level set by the recovery threshold
bits in the ALC control register. If both of these criteria are met,
the gain is recovered by one step (0.5 dB). The gain is incremen-
tally restored to its original value, assuming that the ADC
output level is below the recovery threshold at intervals
determined by the recovery time bits.
If the ADC output level exceeds the recovery threshold while
the PGA gain is being restored, the PGA gain value is held and
does not continue restoration until the ADC output level is
again below the recovery threshold. Once the PGA gain is
restored to its original value, it is not changed again unless the
ADC output value exceeds the attack threshold and the ALC
then enters attack mode. Care should be taken when using this
mode to choose values for the attack and recovery thresholds
that prevent excessive volume modulation caused by continuous
gain adjustments.
Limited Recovery Mode
Limited recovery mode offers a compromise between no recov-
ery and normal recovery modes. If the output level of the ADC
exceeds the attack threshold, attack mode is initiated. When
attack mode has reduced the PGA gain to suitable levels, the
ALC attempts to recover the gain to its original level. If the
ADC output level exceeds the level set by the recovery threshold
bits, a counter is incremented (GAINCNTR). This counter is
incremented at intervals equal to the recovery time selection, if
the ADC has any excursion above the recovery threshold. If the
counter reaches its maximum value, determined by the
GAINCNTR bits in ALC Control Register 1, the PGA gain is
deemed suitable and no further gain recovery is attempted.
Whenever the ADC output level exceeds the attack threshold,
attack mode is reinitiated and the counter is reset.
相关PDF资料 |
PDF描述 |
|---|---|
| MCIMX27LVOP4AR2 | IC LOW END I.MX27 404-MAPBGA |
| AD1938YSTZ | IC CODEC 24BIT 4ADC/8DAC 48LQFP |
| MC56F8335MFGE | IC DIGITAL SIGNAL CTLR 128-LQFP |
| MC9S12XHZ512CAG | IC MCU 16BIT 512 FLASH 144-LQFP |
| MC9S12C96MPBE | IC MCU 96K FLASH 4K RAM 52-LQFP |
相关代理商/技术参数 |
参数描述 |
|---|---|
| ADAV801ASTZ-REEL | 功能描述:IC CODEC AUDIO R-DVD 3.3V 64LQFP RoHS:是 类别:集成电路 (IC) >> 接口 - 编解码器 系列:- 标准包装:2,500 系列:- 类型:立体声音频 数据接口:串行 分辨率（位）:18 b ADC / DAC 数量:2 / 2 三角积分调变:是 S/N 比，标准 ADC / DAC (db):81.5 / 88 动态范围，标准 ADC / DAC (db):82 / 87.5 电压 - 电源，模拟:2.6 V ~ 3.3 V 电压 - 电源，数字:1.7 V ~ 3.3 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:48-WFQFN 裸露焊盘 供应商设备封装:48-TQFN-EP（7x7） 包装:带卷 (TR) |
| ADAV802AST | 制造商:Analog Devices 功能描述:AUDIO CODEC FOR RECORDABLE DVD - Bulk |
| ADAV802ASTZ | 制造商:Analog Devices 功能描述: |
| ADAV803 | 制造商:AD 制造商全称:Analog Devices 功能描述:Audio Codec for Recordable DVD |
| ADAV803AST | 制造商:Analog Devices 功能描述:AUDIO CODEC FOR RECORDABLE DVD - Bulk |
发布紧急采购，3分钟左右您将得到回复。