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參數(shù)資料
| 型號： | AD1953YSTZ |
| 廠商： | Analog Devices Inc |
| 文件頁數(shù)： | 9/36頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC DSP DAC AUDIO3CH/26BIT 48LQFP |
| 產(chǎn)品培訓(xùn)模塊： | Data Converter Fundamentals DAC Architectures |
| 標準包裝： | 1 |
| 系列： | SigmaDSP® |
| 位數(shù)： | 26 |
| 數(shù)據(jù)接口： | 串行 |
| 轉(zhuǎn)換器數(shù)目： | 3 |
| 電壓電源： | 模擬和數(shù)字 |
| 功率耗散（最大）： | 540mW |
| 工作溫度： | -40°C ~ 105°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 48-LQFP |
| 供應(yīng)商設(shè)備封裝： | 48-LQFP（7x7） |
| 包裝： | 托盤 |
| 輸出數(shù)目和類型： | 6 電壓，單極 |
| 采樣率（每秒）： | 48k |
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REV. 0
AD1953
–17–
In the look-ahead compressor, the gain has already been reduced
by the time the tone-burst signal arrives at the multiplier input.
Note that when using a look-ahead compressor, it is impor-
tant to set the detector hold time to a value that is at least the
same as the look-ahead delay time, or else the compressor
release will start too soon, resulting in an expanded “tail” of a
tone burst signal. The complete flow of the left/right dynamics
processor is shown in Figure 13.
LOOK-UP
TABLE
LINEAR
INTERPOLATION
MODIFIED RMS
DETECTOR WITH
LOG OUTPUT
HIGH BITS (1LSB = 3dB)
LOW BITS
TIME
CONSTANT
HOLD
RELEASE
DELAY
SPI-PROGRAMMABLE
LOOK-AHEAD DELAY
POST-COMPRESSION
GAIN, SPI-
PROGRAMMABLE
UP TO 30dB
2
(L+R)
Figure 13. Complete Dynamics Flow, Main Channels
The detector path works from a sum of left and right channels
((L+R)/2). This is the normal way that compressors are built,
and it counts on the fact that the main instruments in any stereo
mix are seldom recorded deliberately out of phase, especially in
the lower frequencies, which tend to dominate the energy spectrum
of real music.
The compressor is followed by a block known as post-compression
gain. Most compressors are used to reduce the dynamic range of
music by lowering the gain during loud signal passages. This
results in an overall loss of volume. This loss can be made up by
introducing gain after the compressor. In the AD1953, the
coefficient format used is 2.20, which has a maximum floating-
point representation of slightly less than 2.0. This means the
maximum gain that can be achieved in a single instruction is 6 dB.
To get more gain, the program in the AD1953 uses a cascade
of five multipliers to achieve up to 30 dB of post-compression gain.
To program the compressor/limiter, the following formulas may
be used to determine the 22-bit numbers (in 2.20 format) to be
entered into the parameter RAM.
RMS Time Constant
This can be best expressed by entering the time constant in
terms of dB/sec “raw” release rate (without the peak-riding circuit).
The attack rate is a rather complicated formula that depends on
the change in amplitude of the input sine wave.
rms tconst
parameter
release rate
f S
__
. –
.
=
×
10 10
10 0
where
rms_tconst_parameter = fractional number to enter into the
SPI RAM (after converting to 22-bit 2.20 format)
release_rate = release rate of the raw rms detector in dB/sec. This
must be negative. fS = audio sampling rate.
RMS Hold Time
rms holdtime
parameter
f
hold time
S
__
int
_
=×
()
where
rms_holdtime_parameter = integer number to enter into the SPI RAM
fS = audio sample rate
Hold_time = absolute time to wait before starting the release
ramp-down of the detector output
int() = integer part of expression
RMS Release Rate
rms decay
parameter
rms decay
__
int
_
/ .
=
()
1 096
Where rms_decay_parameter = decimal integer number to enter
into the SPI RAM
rms_decay = decay rate in dB/sec
int() = integer part of expression
Look-Ahead Delay
Lookahead delay
parameter
Lookahead delay
f
S
__
_
=×
Where Lookahead_delay = predictive compressor delay in abso-
lute time
fS = audio sample rate
The maximum Lookahead_delay_parameter value is 100.
Post-Compression Gain
Post
compression
gain
parameter
Post
compression
gain
linear
__
_
__
_
=
()
∧ 15
Where Post_compression gain_linear is the linear post-compression
gain
^ = raise to the power
Subwoofer Compressor/Limiter
The subwoofer compressor/limiter differs from the left/right
compressor in the following ways:
1. The subwoofer compressor operates on a weighted sum of left
and right inputs (aa
× Left + bb × Right), where aa and bb are
both programmable.
2. The detector input has a biquad filter in series with the input
in order to implement frequency-dependent compression
thresholds.
3. There is no predictive compression, as presumably the input
signals are filtered to pass only low frequencies, and therefore
transient overshoots are not a problem.
The subwoofer compressor signal flow is shown in Figure 14.
LOOK-UP
TABLE
LINEAR
INTERPOLATION
MODIFIED RMS
DETECTOR WITH
LOG OUTPUT
HIGH BITS (1LSB = 3dB)
LOW BITS
TIME
CONSTANT
HOLD
RELEASE
VIN_SUB = K1
LEFT_IN + K2
RIGHT_IN
POST-COMPRESSION
GAIN, SPI-
PROGRAMMABLE
UP TO 30dB
BIQUAD
FILTER
Figure 14. Signal Flow for Subwoofer Compressor
The biquad filter before the detector can be used to implement
a frequency-dependent compression threshold. For example,
assume that the overload point of the woofer is strongly fre-
quency-dependent. In this case, one would have to set the
compressor threshold to a value that corresponded to the most
sensitive overload frequency of the woofer. If the input signal
happened to be mostly in a frequency range where the woofer
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| AD1953YSTZRL | 功能描述:IC DSP DAC AUDIO3CH/26BIT 48LQFP RoHS:是 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 數(shù)模轉(zhuǎn)換器 系列:SigmaDSP® 標準包裝:47 系列:- 設(shè)置時間:2µs 位數(shù):14 數(shù)據(jù)接口:并聯(lián) 轉(zhuǎn)換器數(shù)目:1 電壓電源:單電源 功率耗散（最大）:55µW 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:28-SSOP（0.209"，5.30mm 寬） 供應(yīng)商設(shè)備封裝:28-SSOP 包裝:管件 輸出數(shù)目和類型:1 電流，單極；1 電流，雙極 采樣率（每秒）:* |
| AD1953YSTZRL7 | 功能描述:IC DSP AUDIO 3CHAN 26BIT 48LQFP RoHS:是 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 數(shù)模轉(zhuǎn)換器 系列:SigmaDSP® 標準包裝:47 系列:- 設(shè)置時間:2µs 位數(shù):14 數(shù)據(jù)接口:并聯(lián) 轉(zhuǎn)換器數(shù)目:1 電壓電源:單電源 功率耗散（最大）:55µW 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:28-SSOP（0.209"，5.30mm 寬） 供應(yīng)商設(shè)備封裝:28-SSOP 包裝:管件 輸出數(shù)目和類型:1 電流，單極；1 電流，雙極 采樣率（每秒）:* |
| AD1954 | 制造商:AD 制造商全稱:Analog Devices 功能描述:SigmaDSP⑩ 3-Channel, 26-Bit Signal Processing DAC |
| AD1954YS | 制造商:Analog Devices 功能描述:DAC 3-CH Delta-Sigma 24-bit 44-Pin MQFP 制造商:Rochester Electronics LLC 功能描述:THREE CHANNEL, 24-BIT SIGMADSP DAC - Bulk |
| AD1954YSRL | 制造商:Analog Devices 功能描述:DAC 3-CH Delta-Sigma 24-bit 44-Pin MQFP T/R |
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