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參數(shù)資料
| 型號(hào)： | PCM1750 |
| 英文描述： | Dual CMOS 18-Bit Monolithic Audio ANALOG-TO-DIGITAL CONVERTER |
| 中文描述： | 雙通道CMOS 18位單片音頻模擬數(shù)字轉(zhuǎn)換器 |
| 文件頁(yè)數(shù)： | 10/18頁(yè) |
| 文件大?。?/td> | 240K |
| 代理商： | PCM1750 |
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PCM1750
10
A Gain Change
Rotates
Transfer
Function
Offset Change
Shifts
Transfer
Function
1FFFF
H
1FFFE
H
00001
00000
H
3FFFF
H
20001
H
20000
H
D
* Gain drift (mostly due to reference drift) rotates the transfer function
around the bipolar zero code (00000 ).
NOTE: As the power supply voltages change (mostly due to the +V
supply), the transfer function rotates around BPZ. See the power
supply rejection specification in the spec table.
0.00V
+2.749979
–20.98μV
–2.75
H
bit-1. The switches of the CDAC and the switches of the
TDAC operate concurrently with each other, that is, when a
decision is made to keep or reject bit-1, the same decision is
made for the correction voltage for bit-1. Even though the
ratio stability of the nichrome resistors used in the TDAC
may not be as good as the poly capacitors, it is inconsequen-
tial because the correction voltage of each bit has a limited
range of adjustment.
The DLE at the major carry (a code change from 111...111
to 000...000; in binary two’s complement coding) is typi-
cally
±
1/2 LSB at the 16-bit level, which is sufficient to
provide 90dB SNR and –30dB low level distortion (–60dB
input). For applications requiring less DLE at the major
carry, a pin is provided for each channel to make an external
MSB adjustment.
DISCUSSION
OF SPECIFICATIONS
RESOLUTION AND DYNAMIC RANGE
The theoretical resolution of the PCM1750 is 18-bits. The
maximum possible number of output codes or counts at 18-
bits is 262,144 or 108dB (calculated by raising 2 to the 18th
power). The relative accuracy of any A/D converter, how-
ever, is more a function of it’s absolute linearity and signal-
to-noise ratio than how many bits of resolution it has. These
more pertinent specifications are described later in this
section.
Dynamic range, as it is usually defined for digital audio
converters, is the measure of THD+N at an effective input
signal level of –60dB referred to 0dB. For the PCM1750 this
value is typically 90dB and a minimum of 88dB (for audio
bandwidth = 20Hz to 24kHz, THD+N at –60db = –30 db typ,
–28dB max; f
IN
= 1kHz and f
S
= 192kHz). Resolution is also
commonly used as a theoretical measure of dynamic range,
but it does not take into account the effects of distortion and
noise at low signal levels.
ANALOG INPUT RANGE
The analog input range for the PCM1750 is a bipolar
±
2.75V
(nominal). Table I gives the precise input/output and volt-
age/code relationships for the PCM1750. Figure 5 shows
these same relationships in a graphical format. It should be
noted that the computed voltage input levels represent center
values (the midpoint between code transitions). Output cod-
ing is in binary two’s complement.
DIGITAL OUTPUT
ANALOG INPUT
VOLTAGE INPUT
262144 LSBs
1 LSB
1FFFF
HEX
00000
HEX
3FFFF
HEX
20000
HEX
Full Scale Range
Minimum Step Size
+Full Scale
Bipolar Zero
Bipolar Zero –1LSB
–Full Scale
5.50000000V
20.98083496
μ
V
+2.74997902V
0.00000000V
–0.00002098V
–2.75000000V
TABLE I. Analog Input to Digital Output Relationships.
From Figure 5, the effects of offset and gain errors can be
visualized. These errors can change value in response to
changes in temperature and/or supply voltage. In addition,
gain error (or the full scale range, FSR) changes in direct
proportion to the VREF
IN
voltage value.
SAMPLE AND HOLD PARAMETERS
Aperture Delay and Uncertainty
Aperture delay is the time required to switch from the
SAMPLE to HOLD mode. This time is typically 10ns for the
PCM1750 and it is constant. Aperture uncertainty (jitter) is
the amount of uncertainty associated with the aperture delay.
Aperture uncertainty affects the overall accuracy of the
converter and is greatest at the maximum input frequency of
the converter. The formula for determining the maximum
input frequency (f
MAX
) for a given error contribution due to
aperture uncertainty is: f
MAX
=(2
X
π
X
t
jitter
X
2
N
)
–1
where
t
jitter
is the RMS aperture uncertainty and 2
N
is the desired
SNR (signal-to-noise ratio) expressed in total number of
quantization levels. A 15-bit SNR, therefore, would be
expressed as 2
15
or 32768. Using the typical PCM1750
aperture jitter of 50ps
rms
and an SNR at the 15-bit level, f
MAX
= (2
X
π
X
50ps
X
32768)
–1
or 97.1kHz. This matches very
closely with the rated dynamic accuracy of the PCM1750
where THD+N = –88dB max. This means the typical aper-
ture jitter of PCM1750 only becomes a factor when input
signals to it exceed 97kHz and/or an SNR greater than 15
bits is desired.
Input Bandwidth
The full power bandwidth of the PCM1750 is that input
frequency above which significant distortion is observed
(THD+N > 10-bits or –60dB for a full scale input signal). In
the data sheet, this number is specified as typically being
500kHz. In wideband operation (when no digital filter is
used) the additional full power bandwidth of the PCM1750
FIGURE 5. Analog Input to Digital Output Diagram.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| PCM1750P | Dual CMOS 18-Bit Monolithic Audio ANALOG-TO-DIGITAL CONVERTER |
| PCM1750U | Dual CMOS 18-Bit Monolithic Audio ANALOG-TO-DIGITAL CONVERTER |
| PCM1753DBQR | 24-BIT, 192 kHz SAMPLING ENHANCED MULTI-LEVEL, DELTA-SIGMA, AUDIO DIGITAL-TO-ANALOG CONVERTER |
| PCM1755DBQR | 24-BIT, 192 kHz SAMPLING ENHANCED MULTI-LEVEL, DELTA-SIGMA, AUDIO DIGITAL-TO-ANALOG CONVERTER |
| PCM1753 | 24-BIT, 192 kHz SAMPLING ENHANCED MULTI-LEVEL, DELTA-SIGMA, AUDIO DIGITAL-TO-ANALOG CONVERTER |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| PCM1750P | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| PCM1750P/PCM1750U | 制造商:BB 制造商全稱(chēng):BB 功能描述:PCM1750P. PCM1750U - Dual CMOS 18-Bit Monolithic Audio ANALOG-TO-DIGITAL CONVERTER |
| PCM1750U | 功能描述:音頻模/數(shù)轉(zhuǎn)換器 IC Dual CMOS 18-Bit Mono A/D Converter RoHS:否 制造商:Wolfson Microelectronics 轉(zhuǎn)換速率: 分辨率: ADC 輸入端數(shù)量: 工作電源電壓: 最大工作溫度: 最小工作溫度: 安裝風(fēng)格: 封裝 / 箱體: 封裝: |
| PCM1750U/1K | 功能描述:音頻模/數(shù)轉(zhuǎn)換器 IC Dual CMOS 18-Bit Mono A/D Converter RoHS:否 制造商:Wolfson Microelectronics 轉(zhuǎn)換速率: 分辨率: ADC 輸入端數(shù)量: 工作電源電壓: 最大工作溫度: 最小工作溫度: 安裝風(fēng)格: 封裝 / 箱體: 封裝: |
| PCM1750U/1KG4 | 功能描述:音頻模/數(shù)轉(zhuǎn)換器 IC Dual CMOS 18-Bit Mono A/D Converter RoHS:否 制造商:Wolfson Microelectronics 轉(zhuǎn)換速率: 分辨率: ADC 輸入端數(shù)量: 工作電源電壓: 最大工作溫度: 最小工作溫度: 安裝風(fēng)格: 封裝 / 箱體: 封裝: |
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