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參數(shù)資料
| 型號： | ADS805 |
| 英文描述： | 12-Bit, 20MHz Sampling ANALOG-TO-DIGITAL CONVERTER |
| 中文描述： | 12位，20MHz的采樣模擬數(shù)字轉(zhuǎn)換器 |
| 文件頁數(shù)： | 9/12頁 |
| 文件大?。?/td> | 260K |
| 代理商： | ADS805 |
9
ADS805
FIGURE 2. DC-Coupled, Single-Ended Input Configuration with DC-level Shift.
INPUT
FULL-SCALE
RANGE
REQUIRED
V
REF
MODE
CONNECT
TO
Internal
2Vp-p
+1V
SEL
V
REF
Internal
5Vp-p
+2.5V
SEL
GND
Internal
2V
≤
FSR < 5V
FSR = 2 x V
REF
1V < V
REF
< 2.5V
V
REF
= 1 + (R
1
/R
2
)
R
1
R
2
V
REF
and SEL
SEL and Gnd
External
1V < FSR < 5V
0.5V < V
REF
< 2.5V
SEL
V
REF
+V
S
Ext. V
REF
TABLE I. Selected Reference Configuration Examples.
V
IN
IN
IN
CM
22
22
100pF
R
T
100pF
+
4.7μF
0.1μF
ADS805
1:n
0.1μF
R
G
FIGURE 3. Transformer Coupled Input.
REFERENCE OPERATION
Integrated into the ADS805 is a bandgap reference circuit
including logic that provides either a +1V or +2.5V refer-
ence output, by simply selecting the corresponding pin-strap
configuration. Different reference voltages can be generated
by the use of two external resistors, which will set a different
gain for the internal reference buffer. For more design
flexibility, the internal reference can be shut off and an
external reference voltage used. Table I provides an over-
view of the possible reference options and pin configura-
tions.
the values of resistors R
1
and R
2
. The bias current of the op
amp may also result in an undesired offset. The selection
criteria for an appropriate op amp should include the input
bias current, output voltage swing, distortion and noise
specification. Note that in this example the overall signal
phase is inverted. To re-establish the original signal polarity
it is always possible to interchange the IN and IN connec-
tions.
SINGLE-ENDED-TO-DIFFERENTIAL
CONFIGURATION (TRANSFORMER COUPLED)
In order to select the best suited interface circuit for the
ADS805, the performance requirements must be known. If
an ac-coupled input is needed for a particular application,
the next step is to determine the method of applying the
signal; either single-ended or differentially. The differential
input configuration may provide a noticeable advantage of
achieving good SFDR performance based on the fact that in
the differential mode the signal swing can be reduced to half
of the swing required for single-ended drive. Secondly, by
driving the ADS805 differentially, the even-order harmonics
will be reduced. Figure 3 shows the schematic for the
suggested transformer coupled interface circuit. The resistor
across the secondary side (R
T
) should be set to get an input
impedance match (e.g., R
T
= n
2
R
G
).
One application example that will benefit from the differen-
tial input configuration is the digitization of IF signals. The
wide track-and-hold input bandwidth makes the ADS805
well suited for IF down conversion in both narrow and
wideband applications. The ADS805 maintains excellent
dynamic performance in multiple Nyquist regions covering
a variety of IF frequencies (see Typical Performance Curves).
Using the ADS805 for direct IF conversion eliminates the
need of an analog mixer along with subsequent functions
like amplifiers and filters thus reducing system cost and
complexity.
V
IN
2Vp-p
0
+1V
–1V
R
F
R
IN
NOTE: R
F
= R
IN
, G = –1
+V
S
+V
S
OPA681
ADS805
R
S
50
R
3
2k
22pF
10
μ
F
+
+2.5V
R
2
R
1
R
4
2k
IN
IN
REFB
(+1V)
V
REF
SEL
REFT
0.1
μ
F
0.1
μ
F
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADS805E | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit 20 MSPS Int/Ext Ref RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS805E/1K | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit 20 MSPS Int/Ext Ref RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS805E/1KG4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit 20 MSPS Int/Ext Ref RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS805EG4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit 20 MSPS Int/Ext Ref RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS805U | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
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