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參數(shù)資料
| 型號： | LTC2285CUP#TRPBF |
| 廠商： | Linear Technology |
| 文件頁數(shù)： | 5/24頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC ADC DUAL 14BIT 125MSPS 64QFN |
| 標準包裝： | 2,000 |
| 位數(shù)： | 14 |
| 采樣率（每秒）： | 125M |
| 數(shù)據接口： | 并聯(lián) |
| 轉換器數(shù)目： | 2 |
| 功率耗散（最大）： | 915mW |
| 電壓電源： | 單電源 |
| 工作溫度： | 0°C ~ 70°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 64-WFQFN 裸露焊盤 |
| 供應商設備封裝： | 64-QFN（9x9） |
| 包裝： | 帶卷 (TR) |
| 輸入數(shù)目和類型： | 2 個單端，雙極; 2 個差分, 雙極 |
LTC2285
13
2285fb
APPLICATIONS INFORMATION
from the input and the held voltage is passed to the ADC
core for processing. As CLK transitions from high to low,
the inputs are reconnected to the sampling 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 2.2μF or greater capacitor.
Input Drive Impedance
As with all high performance, high speed ADCs, the dynamic
performance of the LTC2285 can be inuenced by the input
drive circuitry, particularly the second and third harmonics.
Source impedance and reactance can inuence 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 pos-
sible to minimize the effects of incomplete settling.
For the best performance, it is recommended to have a
source impedance of 100Ω 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 LTC2285 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. Terminating on the trans-
former 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 100Ω 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 below 1MHz.
Figure 3. Single-Ended to Differential
Conversion Using a Transformer
25Ω
0.1μF
AIN
+
AIN
–
12pF
2.2μF
VCM
LTC2285
ANALOG
INPUT
0.1μF
T1
1:1
T1 = MA/COM ETC1-1T
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
2285 F03
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LTC2285IUP | 制造商:Linear Technology 功能描述:ADC Dual Pipelined 125Msps 14-bit Parallel 64-Pin QFN EP |
| LTC2285IUP#PBF | 功能描述:IC ADC DUAL 14BIT 125MSPS 64QFN RoHS:是 類別:集成電路 (IC) >> 數(shù)據采集 - 模數(shù)轉換器 系列:- 標準包裝:1 系列:microPOWER™ 位數(shù):8 采樣率（每秒）:1M 數(shù)據接口:串行，SPI? 轉換器數(shù)目:1 功率耗散（最大）:- 電壓電源:模擬和數(shù)字 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:24-VFQFN 裸露焊盤 供應商設備封裝:24-VQFN 裸露焊盤（4x4） 包裝:Digi-Reel® 輸入數(shù)目和類型:8 個單端，單極 產品目錄頁面:892 (CN2011-ZH PDF) 其它名稱:296-25851-6 |
| LTC2285IUP#TRPBF | 功能描述:IC ADC DUAL 14BIT 125MSPS 64QFN RoHS:是 類別:集成電路 (IC) >> 數(shù)據采集 - 模數(shù)轉換器 系列:- 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:250 系列:- 位數(shù):12 采樣率（每秒）:1.8M 數(shù)據接口:并聯(lián) 轉換器數(shù)目:1 功率耗散（最大）:1.82W 電壓電源:模擬和數(shù)字 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-LQFP 供應商設備封裝:48-LQFP（7x7） 包裝:管件 輸入數(shù)目和類型:2 個單端，單極 |
| LTC2285IUP-3CGPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Dual 14-Bit, 135Msps Low Power 3.3V ADC |
| LTC2285IUPPBF | 制造商:Linear Technology 功能描述:ADC, Dual 14b 125Msps, 3V, LTC2285IUP |
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