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參數(shù)資料
| 型號： | LTC2274IUJ |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | ADC |
| 英文描述： | 1-CH 16-BIT PROPRIETARY METHOD ADC, SERIAL ACCESS, PQCC40 |
| 封裝： | 6 X 6 MM, PLASTIC, QFN-40 |
| 文件頁數(shù)： | 11/40頁 |
| 文件大小： | 897K |
| 代理商： | LTC2274IUJ |
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LTC2274
19
2274fb
APPLICATIONS INFORMATION
INPUT DRIVE CIRCUITS
Input Filtering
A rst order RC lowpass lter at the input of the ADC can
serve two functions: limit the noise from input circuitry and
provide isolation from ADC S/H switching. The LTC2274
has a very broadband S/H circuit, DC to 700MHz; it can
be used in a wide range of applications; therefore, it is not
possible to provide a single recommended RC lter.
Figures 3, 4a and 4b show three examples of input RC
ltering at three ranges of input frequencies. In general
it is desirable to make the capacitors as large as can be
tolerated—this will help suppress random noise as well
as noise coupled from the digital circuitry. The LTC2274
does not require any input lter to achieve data sheet
specications; however, no ltering will put more stringent
noise requirements on the input drive circuitry.
Transformer Coupled Circuits
Figure 3 shows the LTC2274 being driven by an RF trans-
former with a center-tapped secondary. The secondary
center tap is DC biased with VCM, setting the ADC input
signal at its optimum DC level. Figure 3 shows a 1:1 turns
ratio transformer. Other turns ratios can be used; however,
as the turns ratio increases so does the impedance seen by
the ADC. Source impedance greater than 50
Ω can reduce
the input bandwidth and increase high frequency distor-
tion. A disadvantage of using a transformer is the loss of
low frequency response. Most small RF transformers have
poor performance at frequencies below 1MHz.
Center-tapped transformers provide a convenient means
of DC biasing the secondary; however, they often show
poor balance at high input frequencies, resulting in large
2nd order harmonics.
Figure 4a shows transformer coupling using a transmis-
sion line balun transformer. This type of transformer has
much better high frequency response and balance than
ux coupled center tap transformers. Coupling capacitors
are added at the ground and input primary terminals to
allow the secondary terminals to be biased at 1.25V. Figure
4b shows the same circuit with components suitable for
higher input frequencies.
0.1μF
AIN
+
AIN
–
4.7pF
2.2μF
4.7pF
VCM
LTC2274
ANALOG
INPUT
0.1μF
T1
1:1
T1 = MA/COM ETC1-1-13
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
EXCEPT 2.2μF
2274 F04a
5Ω
10Ω
25Ω
10Ω
5Ω
Figure 4a. Using a Transmission Line Balun Transformer.
Recommended for Input Frequencies from 100MHz to 250MHz
0.1μF
AIN
+
AIN
–
2.2μF
2.2pF
VCM
LTC2274
ANALOG
INPUT
0.1μF
T1
1:1
T1 = MA/COM ETC1-1-13
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
EXCEPT 2.2μF
2274 F04b
5Ω
25Ω
5Ω
Figure 4b. Using a Transmission Line Balun Transformer.
Recommended for Input Frequencies from 250MHz to 500MHz
Figure 3. Single-Ended to Differential Conversion
Using a Transformer. Recommended for Input
Frequencies from 5MHz to 150MHz
35Ω
50Ω
35Ω
10Ω
5Ω
0.1μF
AIN
+
AIN
–
8.2pF
2.2μF
8.2pF
VCM
LTC2274
T1
T1 = MA/COM ETC1-1T
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
EXCEPT 2.2μF
2274 F03
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
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| LTC2274IUJ#PBF | 制造商:Linear Technology 功能描述:ADC Single Pipelined 105Msps 16-bit Serial 40-Pin QFN EP 制造商:Linear Technology 功能描述:IC ADC 16-BIT 105MSPS 40-QFN 制造商:Linear Technology 功能描述:IC ADC 16BIT 105MSPS QFN-40 制造商:Linear Technology 功能描述:IC, ADC, 16BIT, 105MSPS, QFN-40; Resolution (Bits):16bit; Sampling Rate:105MSPS; Supply Voltage Type:Single; Supply Voltage Min:3.135V; Supply Voltage Max:3.465V; Supply Current:394mA; Digital IC Case Style:QFN; No. of Pins:40 ;RoHS Compliant: Yes |
| LTC2274IUJ#TRPBF | 制造商:Linear Technology 功能描述:ADC Single Pipelined 105Msps 16-bit Serial 40-Pin QFN EP T/R 制造商:Linear Technology 功能描述:IC ADC 16-BIT 105MSPS 40-QFN |
| LTC2274IUJ-PBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:16-Bit, 105Msps Serial Output ADC |
| LTC2274IUJ-TR | 制造商:LINER 制造商全稱:Linear Technology 功能描述:16-Bit, 105Msps Serial Output ADC |
| LTC2274IUJ-TRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:16-Bit, 105Msps Serial Output ADC |
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