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参数资料
| 型号： | DC1620A-H |
| 厂商： | Linear Technology |
| 文件页数： | 13/38页 |
| 文件大小： | 0K |
| 描述： | BOARD DEMO 105MSPS LTC2144-14 |
| 软件下载： | QuikEval II System |
| 设计资源： | DC1620A Design Files DC1620A Schematic |
| 标准包装： | 1 |
| 系列： | * |
| 相关产品： | DC890B-ND - BOARD USB DATA COLLECTION |
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LTC2145-14/
LTC2144-14/LTC2143-14
20
21454314fa
CONVERTER OPERATION
The LTC2145-14/LTC2144-14/LTC2143-14 are low power,
two-channel, 14-bit, 125Msps/105Msps/80Msps A/D
converters that are powered by a single 1.8V supply. The
analog inputs should be driven differentially. The encode
input can be driven differentially, or single ended for lower
power consumption. The digital outputs can be CMOS,
double data rate CMOS (to halve the number of output
lines), or double data rate LVDS (to reduce digital noise
in the system.) Many additional features can be chosen
by programming the mode control registers through a
serial SPI port.
ANALOG INPUT
The analog inputs are differential CMOS sample-and-hold
circuits (Figure 2). The inputs should be driven differen-
tially around a common mode voltage set by the VCM1 or
VCM2 output pins, which are nominally VDD/2. For the 2V
input range, the inputs should swing from VCM – 0.5V
to VCM + 0.5V. There should be 180° phase difference
between the inputs.
The two channels are simultaneously sampled by a shared
encode circuit (Figure 2).
Single-Ended Input
For applications less sensitive to harmonic distortion, the
AIN+ input can be driven single-ended with a 1VP-P signal
centered around VCM. The AIN– input should be connected
to VCM and the VCM bypass capacitor should be increased
to 2.2μF. With a single-ended input, the harmonic distortion
and INL will degrade, but the noise and DNL will remain
unchanged.
INPUT DRIVE CIRCUITS
Input Filtering
If possible, there should be an RC lowpass filter right at
the analog inputs. This lowpass filter isolates the drive
circuitry from the A/D sample-and-hold switching, and
also limits wideband noise from the drive circuitry. Figure 3
shows an example of an input RC filter. The RC component
values should be chosen based on the application’s input
frequency.
Transformer Coupled Circuits
Figure 3 shows the analog input being driven by an RF
transformer with a center-tapped secondary. The center
tap is biased with VCM, setting the A/D input at its optimal
DC level. At higher input frequencies a transmission line
balun transformer (Figure 4 to Figure 6) has better balance,
resulting in lower A/D distortion.
CSAMPLE
5pF
RON
15Ω
RON
15Ω
VDD
LTC2145-14
AIN
+
21454314 F02
CSAMPLE
5pF
VDD
AIN
–
ENC–
ENC+
1.2V
10k
1.2V
10k
CPARASITIC
1.8pF
CPARASITIC
1.8pF
10Ω
25Ω
50Ω
0.1μF
AIN
+
AIN
–
12pF
0.1μF
VCM
LTC2145-14
ANALOG
INPUT
0.1μF
T1
1:1
T1: MA/COM MABAES0060
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
21454314 F03
Figure 2. Equivalent Input Circuit. Only One of the Two
Analog Channels Is Shown
Figure 3. Analog Input Circuit Using a Transformer.
Recommended for Input Frequencies from 5MHz to 70MHz
APPLICATIONS INFORMATION
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相关代理商/技术参数 |
参数描述 |
|---|---|
| DC1620A-I | 功能描述:BOARD DEMO 80MSPS LTC2143-14 RoHS:是 类别:未定义的类别 >> 其它 系列:* 标准包装:1 系列:* 其它名称:MS305720A |
| DC1620A-J | 功能描述:BOARD DEMO 65MSPS LTC2142-14 RoHS:是 类别:未定义的类别 >> 其它 系列:* 标准包装:1 系列:* 其它名称:MS305720A |
| DC1620A-K | 功能描述:BOARD DEMO 40MSPS LTC2141-14 RoHS:是 类别:未定义的类别 >> 其它 系列:* 标准包装:1 系列:* 其它名称:MS305720A |
| DC1620A-L | 功能描述:BOARD DEMO 25MSPS LTC2140-14 RoHS:是 类别:未定义的类别 >> 其它 系列:* 标准包装:1 系列:* 其它名称:MS305720A |
| DC1620A-M | 功能描述:BOARD DEMO 125MSPS LTC2145-12 RoHS:是 类别:未定义的类别 >> 其它 系列:* 标准包装:1 系列:* 其它名称:MS305720A |
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