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| 型号： | AD7781BRZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 7/16页 |
| 文件大小： | 0K |
| 描述： | IC ADC 20BIT 1CH LP SD 14SOIC |
| 产品培训模块： | Weigh Scale Introduction |
| 设计资源： | Weigh Scale Design Using AD7781 with Internal PGA (CN0108) |
| 标准包装： | 56 |
| 位数： | 20 |
| 采样率（每秒）： | 16.7 |
| 数据接口： | 串行，SPI? |
| 转换器数目： | 1 |
| 电压电源： | 单电源 |
| 工作温度： | -40°C ~ 105°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 14-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 14-SO |
| 包装： | 管件 |
| 输入数目和类型： | 1 个差分，双极 |
| 产品目录页面： | 779 (CN2011-ZH PDF) |
AD7781
Rev. 0 | Page 15 of 16
GROUNDING AND LAYOUT
Because the analog input and reference input of the ADC are
differential, most of the voltages in the analog modulator are
common-mode voltages. The excellent common-mode reject-
tion of the part removes common-mode noise on these inputs.
The digital filter provides rejection of broadband noise on the
power supply, except at integer multiples of the modulator
sampling frequency. The digital filter also removes noise from
the analog and reference inputs, provided that these noise sources
do not saturate the analog modulator. As a result, the AD7781
is more immune to noise interference than conventional high
resolution converters. However, because the resolution of the
AD7781 is so high and the noise levels from the AD7781 are so
low, care must be taken with regard to grounding and layout.
The printed circuit board (PCB) that houses the AD7781 should
be designed so that the analog and digital sections are separated
and confined to certain areas of the board. A minimum etch
technique is generally best for ground planes because it gives
the best shielding.
It is recommended that the GND pin of the AD7781 be tied
to the AGND plane of the system. In any layout, pay attention
to the flow of currents in the system and ensure that the return
paths for all currents are as close as possible to the paths that the
currents took to reach their destinations. Avoid forcing digital
currents to flow through the AGND sections of the layout.
The ground plane of the AD7781 should be allowed to run under
the AD7781 to prevent noise coupling. The power supply lines
to the AD7781 should use as wide a trace as possible to provide
low impedance paths and reduce the effects of glitches on the
power supply line. Fast switching signals such as clocks should
be shielded with digital ground to avoid radiating noise to other
sections of the board, and clock signals should never be run near
the analog inputs. Avoid crossover of digital and analog signals.
Traces on opposite sides of the board should run at right angles
to each other. This reduces the effects of feedthrough through
the board. A microstrip technique is by far the best, but it is not
always possible with a double-sided board. In this technique,
the component side of the board is dedicated to ground planes,
and the signals are placed on the solder side.
Good decoupling is important when using high resolution ADCs.
AVDD should be decoupled with 10 μF tantalum capacitors in
parallel with 0.1 μF capacitors to GND. DVDD should be decoupled
with 10 μF tantalum capacitors in parallel with 0.1 μF capac-
itors to GND, with the system’s AGND to DGND connection
being close to the AD7781. To achieve the best results from
these decoupling components, place them as close as possible
to the device, ideally right up against the device. All logic chips
should be decoupled with 0.1 μF ceramic capacitors to DGND.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD7781BRZ | 制造商:Analog Devices 功能描述:IC ADC 20BIT 16.7SPS SOIC-14 |
| AD7781BRZ-REEL | 功能描述:IC ADC 20BIT 1CH LP SD 14SOIC RoHS:是 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:2,500 系列:- 位数:16 采样率（每秒）:15 数据接口:MICROWIRE?，串行，SPI? 转换器数目:1 功率耗散（最大）:480µW 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:38-WFQFN 裸露焊盘 供应商设备封装:38-QFN（5x7） 包装:带卷 (TR) 输入数目和类型:16 个单端，双极；8 个差分，双极 配用:DC1011A-C-ND - BOARD DELTA SIGMA ADC LTC2494 |
| AD7781CRUZ | 功能描述:IC ADC 20BIT 1CH LP SD 16TSSOP 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 |
| AD7781CRUZ-REEL | 功能描述:IC ADC 20BIT 1CH LP SD 16TSSOP RoHS:是 类别:集成电路 (IC) >> 数据采集 - 模数转换器 系列:- 标准包装:2,500 系列:- 位数:16 采样率（每秒）:15 数据接口:MICROWIRE?，串行，SPI? 转换器数目:1 功率耗散（最大）:480µW 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:38-WFQFN 裸露焊盘 供应商设备封装:38-QFN（5x7） 包装:带卷 (TR) 输入数目和类型:16 个单端，双极；8 个差分，双极 配用:DC1011A-C-ND - BOARD DELTA SIGMA ADC LTC2494 |
| AD7781CRZ | 功能描述:IC ADC 20BIT 1CH LP SD 14SOIC 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:16 采样率（每秒）:45k 数据接口:串行 转换器数目:2 功率耗散（最大）:315mW 电压电源:模拟和数字 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:28-SOIC（0.295"，7.50mm 宽） 供应商设备封装:28-SOIC W 包装:带卷 (TR) 输入数目和类型:2 个单端，单极 |
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