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参数资料
| 型号： | AD73322AR |
| 厂商： | ANALOG DEVICES INC |
| 元件分类： | 通信及网络 |
| 英文描述： | Low Cost, Low Power CMOS General-Purpose Dual Analog Front End |
| 中文描述： | SPECIALTY TELECOM CIRCUIT, PDSO28 |
| 封装： | SOIC-28 |
| 文件页数： | 25/40页 |
| 文件大小： | 437K |
| 代理商： | AD73322AR |
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REV. 0
AD73322L
–25–
The device features an on-chip master clock divider circuit that
allows the sample rate to be reduced as the sampling rate of the
sigma-delta converter is proportional to the output of the MCLK
Divider (whose default state is divide-by-one).
The decimator
’
s frequency response (Sinc3) gives some pass-
band attenuation (up to F
S
/2) which continues to roll off above
the Nyquist frequency. If it is required to implement a digital
filter to create a sharper cutoff characteristic, it may be prudent
to use an initial sample rate of greater than twice the Nyquist
rate in order to avoid aliasing due to the smooth roll-off of the
Sinc3 filter response.
In the case of voiceband processing where 4 kHz represents the
Nyquist frequency, if the signal to be measured were externally
bandlimited then an 8 kHz sampling rate would suffice. How-
ever if it is required to limit the bandwidth using a digital filter,
then it may be more appropriate to use an initial sampling rate
of 16 kHz and to process this sample stream with a filtering and
decimating algorithm to achieve a 4 kHz bandlimited signal at
an 8 kHz rate. Figure 19 details the initial 16 kHz sampled tone.
FREQUENCY
–
Hz
0
1000
0
–
20
d
–
40
–
60
–
80
–
100
–
120
2000
3000
4000
5000
6000
7000
8000
–
140
Figure 19. FFT (ADC 16 kHz Direct Sampling)
Figure 20 details the spectrum of the final 8 kHz sampled fil-
tered tone.
FREQUENCY
–
Hz
0
500
0
–
20
d
–
40
–
60
–
80
–
100
–
120
1000
1500
2000
2500
3000
3500
4000
–
140
Figure 20. FFT (ADC 8 kHz Filtered and Decimated from
16 kHz)
Encoder Group Delay
When programmed for high sampling rates, the AD73322L
offers a very low level of group delay, which is given by the
following relationship:
Group Delay
(
Decimator
)
= Order
×
((
M – 1
)
/2
)
×
T
DEC
where:
Order
is the order of the decimator (= 3),
M
is the decimation factor (= 32 @ 64 kHz, = 64 @ 32 kHz,
= 128 @ 16 kHz , = 256 @ 8 kHz) and
T
DEC
is the decimation sample interval (= 1/2.048e6) (based
on DMCLK = 16.384 MHz) => Group Delay (Decimator @
64 kHz) = 3
×
(32
–
1)/2
×
(1/2.048e6) = 22.7
μ
s
If final filtering is implemented in the DSP, the final filter
’
s
group delay must be taken into account when calculating overall
group delay.
Decoder Section
The decoder section updates (samples) at the same rate as the
encoder section. This rate is programmable as 64 kHz, 32 kHz,
16 kHz or 8 kHz (from a 16.384 MHz MCLK). The decoder
section represents a reverse of the process that was described in
the encoder section. In the case of the decoder section, signals
are applied in the form of samples at an initial low rate. This
sample rate is then increased to the final digital sigma-delta
modulator rate of DMCLK/8 by interpolating new samples
between the original samples. The interpolating filter also has the
action of canceling images due to the interpolation process using
spectral nulls that exist at integer multiples of the initial sampling
rate. Figure 21 shows the spectral response of the decoder section
sampling at 64 kHz. Again, its sigma-delta modulator shapes the
noise so it is reduced in the voice bandwidth dc
–
4 kHz. For
improved voiceband SNR, the user can implement an initial
anti-imaging filter, preceded by 8 kHz to 64 kHz interpolation,
in the DSP.
FREQUENCY
–
Hz
0
0.5
0
d
–
20
1.0
1.5
2.0
2.5
3.0
3.5
–
100
–
10
–
30
–
40
–
50
–
60
–
70
–
80
–
90
10
4
Figure 21. FFT (DAC 64 kHz Sampling)
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD73322AR-REEL | 制造商:Analog Devices 功能描述:Audio Codec 2ADC / 2DAC 16-Bit 28-Pin SOIC W T/R |
| AD73322AR-REEL7 | 制造商:Analog Devices 功能描述:Audio Codec 2ADC / 2DAC 16-Bit 28-Pin SOIC W T/R |
| AD73322ARZ | 制造商:Analog Devices 功能描述:Audio Codec 2ADC / 2DAC 16-Bit 28-Pin SOIC W 制造商:Analog Devices 功能描述:AUD CODEC 2ADC / 2DAC 16BIT 28SOIC - Trays 制造商:Analog Devices 功能描述:Dual Voice Band Codec 16-Bit 3/5V SOIC28 |
| AD73322ARZ-REEL | 制造商:Analog Devices 功能描述:DUAL VOICE BAND ANALOG FRONT END IC (ROHS) - Tape and Reel 制造商:Analog Devices 功能描述:DUAL VOICEBAND ANALOG FRONT END IC |
| AD73322ARZ-REEL7 | 制造商:Analog Devices 功能描述:DUAL VOICEBAND CODEC - Tape and Reel |
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