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參數(shù)資料
| 型號： | ADC12191CIVT |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | ADC |
| 英文描述： | 12-Bit, 10 MHz Self-Calibrating, Pipelined A/D Converter with Internal Sample & Hold |
| 中文描述： | 1-CH 12-BIT PROPRIETARY METHOD ADC, PARALLEL ACCESS, PQFP32 |
| 封裝： | TQFP-32 |
| 文件頁數(shù)： | 13/16頁 |
| 文件大?。?/td> | 278K |
| 代理商： | ADC12191CIVT |
Applications Information
(Continued)
5.0 Layout and Grounding
Proper grounding and routing of all signals is essential to en-
sure accurate conversion. Separate analog and digital
ground planes that are connected beneath the ADC12191
are required to achieve specified performance. The analog
and digital grounds may be in the same layer, but should be
separated from each other and should never overlap each
other. Separation should be at least 1/8 inch, where pos-
sible.
The ground return for the digital output buffer supply (DGND
I/O) carries the ground current for the output drivers. This pin
should be connected to the system digital ground. The cur-
rent on this pin can exhibit high transients that could add
noise to the conversion process. To prevent this from hap-
pening, the DGND I/O pin should NOT be connected in close
proximity to any of the ADC12191’s other ground pins.
Capacitive coupling between the typically noisy digital
ground plane and the sensitive analog circuitry can lead to
poor performance that may seem impossible to isolate and
remedy. The solution is to keep the analog circuitry sepa-
rated from the digital circuitry and from the digital ground
plane.
Digital circuits create substantial supply and ground current
transients. The logic noise thus generated could have signifi-
cant impact upon system noise performance. The best logic
family to use in systems with A/D converters is one which
employs non-saturating transistor designs, or has low noise
characteristics, such as the 74LS, 74HC(T) and 74 AC(T)Q
families. The worst noise generators are logic families that
draw the largest supply current transients during clock or sig-
nal edges, like the 74F and the 74AC(T) families.
Since digital switching transients are composed largely of
high frequency components, total ground plane copper
weight will have little effect upon the logic-generated noise.
This is because of the skin effect. Total surface area is more
important than is total ground plane volume.
An effective way to control ground noise is by connecting the
analog and digital ground planes together beneath the ADC
with a copper trace that is very narrow compared with the
rest of the ground plane. This narrowing beneath the con-
verter provides a fairly high impedance to the high frequency
components of the digital switching currents, directing them
away from the analog pins. The relatively lower frequency
analog ground currents do not create a significant voltage
drop across the impedance of this narrow ground connec-
tion.
To maximize accuracy in high speed, high resolution sys-
tems, avoid crossing analog and digital signal traces. It is im-
portant to keep any clock lines isolated from ALL other lines.
Even the generally accepted 90 degree crossing should be
avoided as even a little coupling can cause problems at high
frequencies. This is because other lines can introduce phase
noise (jitter) into the clock line, which can lead to degradation
of SNR.
DS101040-23
FIGURE 5. Basic Connections Diagram
A
www.national.com
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相關(guān)代理商/技術(shù)參數(shù) |
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| ADC121C021 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:I2C-Compatible, 12-Bit Analog-to-Digital Converter (ADC) with Alert Function |
| ADC121C021CIMK | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADC121C021CIMK/NOPB | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADC121C021CIMKX | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:I2C-Compatible, 12-Bit Analog-to-Digital Converter (ADC) with Alert Function |
| ADC121C021CIMKX/NOPB | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
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