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参数资料
| 型号： | LTC2251CUH#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 6/24页 |
| 文件大小： | 0K |
| 描述： | IC ADC 10-BIT 125MSPS 3V 32-QFN |
| 标准包装： | 73 |
| 位数： | 10 |
| 采样率（每秒）： | 125M |
| 数据接口： | 并联 |
| 转换器数目： | 1 |
| 功率耗散（最大）： | 468mW |
| 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： | 32-WFQFN 裸露焊盘 |
| 供应商设备封装： | 32-QFN 裸露焊盘（5x5） |
| 包装： | 管件 |
| 输入数目和类型： | 1 个单端，双极; 1 个差分，双极 |
| 产品目录页面： | 1349 (CN2011-ZH PDF) |
LTC2251/LTC2250
14
22510fa
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 LTC2251/LTC2250 can be
influenced by the input drive circuitry, particularly the
second and third harmonics. Source impedance and reac-
tance can influence SFDR. At the falling edge of CLK, the
sample-and-hold circuit will connect the 3.5pF 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
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 LTC2251/LTC2250 being driven by an
RF transformer with a center tapped secondary. 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 trans-
former. 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 trans-
formers have poor performance at frequencies below
1MHz.
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
APPLICATIO S I FOR ATIO
WU
UU
frequency input response; however, the limited gain band-
width of most op amps will limit the SFDR at high input
frequencies.
Figure 5 shows a single-ended input circuit. The imped-
ance seen by the analog inputs should be matched. This
circuit is not recommended if low distortion is required.
The 25
resistorsand12pFcapacitorontheanaloginputs
serve two purposes: isolating the drive circuitry from the
Figure 3. Single-Ended to Differential
Conversion Using a Transformer
25
25
25
25
0.1
F
AIN
+
AIN
–
12pF
2.2
F
VCM
LTC2251/
LTC2250
ANALOG
INPUT
0.1
FT1
1:1
T1 = MA/COM ETC1-1T
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
22510 F03
Figure 4. Differential Drive with an Amplifier
25
25
12pF
2.2
F
VCM
22510 F04
–
+
CM
ANALOG
INPUT
HIGH SPEED
DIFFERENTIAL
AMPLIFIER
AIN
+
AIN
–
LTC2251/
LTC2250
Figure 5. Single-Ended Drive
25
0.1
F
ANALOG
INPUT
VCM
AIN
+
AIN
–
1k
12pF
22510 F05
2.2
F
1k
25
0.1
F
LTC2251/
LTC2250
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC2251IUH | 制造商:LINER 制造商全称:Linear Technology 功能描述:10-Bit, 125/105Msps Low Noise 3V ADCs |
| LTC2251IUH#PBF | 功能描述:IC ADC 10-BIT 125MSPS 3V 32-QFN 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 系列:- 位数:14 采样率（每秒）:83k 数据接口:串行，并联 转换器数目:1 功率耗散（最大）:95mW 电压电源:双 ± 工作温度:0°C ~ 70°C 安装类型:通孔 封装/外壳:28-DIP（0.600"，15.24mm） 供应商设备封装:28-PDIP 包装:管件 输入数目和类型:1 个单端，双极 |
| LTC2251IUH#TRPBF | 功能描述:IC ADC 10BIT 125MSPS 3V 32-QFN 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 |
| LTC2252 | 制造商:LINER 制造商全称:Linear Technology 功能描述:14-Bit, 125/105Msps Low Power 3V ADCs |
| LTC2252CUH | 制造商:Linear Technology 功能描述:Single ADC Pipelined 105Msps 12-bit Parallel 32-Pin QFN EP |
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