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| 型号： | LTC2291IUP#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 9/28页 |
| 文件大小： | 0K |
| 描述： | IC ADC DUAL 12BIT 25MSPS 64QFN |
| 标准包装： | 40 |
| 位数： | 12 |
| 采样率（每秒）： | 25M |
| 数据接口： | 并联 |
| 转换器数目： | 2 |
| 功率耗散（最大）： | 180mW |
| 电压电源： | 单电源 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 64-WFQFN 裸露焊盘 |
| 供应商设备封装： | 64-QFN（9x9） |
| 包装： | 管件 |
| 输入数目和类型： | 2 个单端，双极; 2 个差分, 双极 |
| 产品目录页面： | 1349 (CN2011-ZH PDF) |
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LTC2293/LTC2292/LTC2291
17
229321fa
capacitors to acquire a new sample. Since the sampling
capacitors still hold the previous sample, a charging glitch
proportional to the change in voltage between samples will
be seen at this time. If the change between the last sample
and the new sample is small, the charging glitch seen at
the input will be small. If the input change is large, such as
the change seen with input frequencies near Nyquist, then
a larger charging glitch will be seen.
Single-Ended Input
For cost sensitive applications, the analog inputs can be
driven single-ended. With a single-ended input the har-
monic distortion and INL will degrade, but the SNR and
DNL will remain unchanged. For a single-ended input, AIN+
should be driven with the input signal and AIN– should be
connected to 1.5V or VCM.
Common Mode Bias
For optimal performance the analog inputs should be
driven differentially. Each input should swing
±0.5V for
the 2V range or
±0.25V for the 1V range, around a
common mode voltage of 1.5V. The VCM output pin may
be used to provide the common mode bias level. VCM can
be tied directly to the center tap of a transformer to set the
DC input level or as a reference level to an op amp
differential driver circuit. The VCM pin must be bypassed to
ground close to the ADC with a 2.2
F or greater capacitor.
Input Drive Impedance
As with all high performance, high speed ADCs, the
dynamic performance of the LTC2293/LTC2292/LTC2291
can be influenced by the input drive circuitry, particularly
the second and third harmonics. Source impedance and
reactance can influence SFDR. At the falling edge of CLK,
the sample-and-hold circuit will connect the 4pF sampling
capacitor to the input pin and start the sampling period.
The sampling period ends when CLK rises, holding the
sampled input on the sampling capacitor. Ideally the input
circuitry should be fast enough to fully charge
the sampling capacitor during the sampling period
1/(2FENCODE); however, this is not always possible and the
incomplete settling may degrade the SFDR. The sampling
APPLICATIO S I FOR ATIO
WU
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glitch has been designed to be as linear as possible to
minimize the effects of incomplete settling.
For the best performance, it is recommended to have a
source impedance of 100
or less for each input. The
source impedance should be matched for the differential
inputs. Poor matching will result in higher even order
harmonics, especially the second.
Input Drive Circuits
Figure 3 shows the LTC2293/LTC2292/LTC2291 being
driven by an RF transformer with a center tapped second-
ary. The secondary center tap is DC biased with VCM,
setting the ADC input signal at its optimum DC level.
Terminating on the transformer secondary is desirable, as
this provides a common mode path for charging glitches
caused by the sample and hold. Figure 3 shows a 1:1 turns
ratio transformer. Other turns ratios can be used if the
source impedance seen by the ADC does not exceed 100
for each ADC input. A disadvantage of using a transformer
is the loss of low frequency response. Most small RF
transformers have poor performance at frequencies be-
low 1MHz.
Figure 3. Single-Ended to Differential Conversion
Using a Transformer
25
25
25
25
0.1
F
AIN
+
AIN
–
12pF
2.2
F
VCM
LTC2293
LTC2292
LTC2291
ANALOG
INPUT
0.1
FT1
1:1
T1 = MA/COM ETC1-1T
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
229321 F03
Figure 4 demonstrates the use of a differential amplifier to
convert a single ended input signal into a differential input
signal. The advantage of this method is that it provides low
frequency input response; however, the limited gain band-
width of most op amps will limit the SFDR at high input
frequencies.
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相关代理商/技术参数 |
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|---|---|
| LTC2291UP | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual 12-Bit, 65/40/25Msps Low Power 3V ADCs |
| LTC2292 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual 12-Bit, 65/40/25Msps Low Power 3V ADCs |
| LTC2292CUP | 制造商:Linear Technology 功能描述:ADC Dual Pipelined 40Msps 12-bit Parallel 64-Pin QFN EP |
| LTC2292CUP#PBF | 功能描述:IC ADC DUAL 12BIT 40MSPS 64QFN RoHS:是 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 其它有关文件:TSA1204 View All Specifications 标准包装:1 系列:- 位数:12 采样率（每秒）:20M 数据接口:并联 转换器数目:2 功率耗散（最大）:155mW 电压电源:模拟和数字 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:48-TQFP 供应商设备封装:48-TQFP（7x7） 包装:Digi-Reel® 输入数目和类型:4 个单端，单极；2 个差分，单极 产品目录页面:1156 (CN2011-ZH PDF) 其它名称:497-5435-6 |
| LTC2292CUP#TRPBF | 功能描述:IC ADC DUAL 12BIT 40MSPS 64QFN RoHS:是 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:1,000 系列:- 位数:12 采样率（每秒）:300k 数据接口:并联 转换器数目:1 功率耗散（最大）:75mW 电压电源:单电源 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:24-SOIC（0.295"，7.50mm 宽） 供应商设备封装:24-SOIC 包装:带卷 (TR) 输入数目和类型:1 个单端，单极；1 个单端，双极 |
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