参数资料
| 型号： | AD7745ARUZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 15/28页 |
| 文件大小： | 0K |
| 描述： | IC CONV 1CH CAP TO DGTL 16TSSOP |
| 设计资源： | Extending the Capacitive Input Range of AD7745/AD7746 (CN0129) |
| 标准包装： | 96 |
| 类型： | 电容数字转换器 |
| 分辨率（位）： | 24 b |
| 数据接口： | 串行 |
| 电压电源： | 单电源 |
| 电源电压： | 2.7 V ~ 5.25 V |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-TSSOP（0.173"，4.40mm 宽） |
| 供应商设备封装： | 16-TSSOP |
| 包装： | 管件 |
| 产品目录页面： | 781 (CN2011-ZH PDF) |
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AD7745/AD7746
Rev. 0 | Page 22 of 28
0x000000 ... 0xFFFFFF
DATA
CAPDIFF = 1
± 4pF
CDC
EXC
CIN(+)
CIN(–)
CX
15 ... 19pF
(17
± 2pF)
CY
15 ... 19pF
(17
± 2pF)
CAPDAC(+)
17pF
CAPDAC(–)
17pF
05468-021
Figure 34. Using CAPDAC in Differential Mode
0x000000 ... 0xFFFFFF
DATA
CAPDIFF = 1
± 4pF
CDC
EXC
CIN(+)
CIN(–)
CX
13 ... 21pF
(17
± 4pF)
CY
17pF
CAPDAC(+)
17pF
CAPDAC(–)
17pF
05468-011
Figure 35. Using CAPDAC in Differential Mode
PARASITIC CAPACITANCE TO GROUND
DATA
CDC
EXC
CGND1
CIN
CGND2
CX
05468-012
Figure 36. Parasitic Capacitance to Ground
The CDC architecture used in the AD7745/AD7746 measures
the capacitance CX connected between the EXC pin and the
CIN pin. In theory, any capacitance CP to ground should not
affect the CDC result (see Figure 36).
The practical implementation of the circuitry in the chip
implies certain limits and the result is gradually affected by
capacitance to ground. See the allowed capacitance to GND in
the specification table for CIN and excitation. Also see the
typical performance characteristics shown in Figure 9, Figure
10, and Figure 11.
PARASITIC RESISTANCE TO GROUND
DATA
CDC
EXC
RGND1
CIN
RGND2
CX
05468-013
Figure 37. Parasitic Resistance to Ground
The AD7745/AD7746 CDC result would be affected by a leak-
age current from the CX to ground, therefore the CX should be
isolated from the ground. The influence of the leakage current
varies with the power supply voltage. The following limits can
be used as a guideline for the allowed leakage current or the
VDD ≈ 5 V: IGND < 150 nA (that is, RGND > 30 M)
VDD ≥ 3 V: IGND < 60 nA (that is, RGND > 50 M)
VDD ≥ 2.7 V: IGND < 30 nA (that is, RGND > 100 M)
A higher leakage current to ground results in a gain error, an
offset error, and a nonlinearity error. See the typical
performance characteristics shown in Figure 12 and Figure 13.
PARASITIC PARALLEL RESISTANCE
DATA
CDC
EXC
CIN
RP
05468-022
CX
Figure 38. Parasitic Parallel Resistance
The AD7745/AD7746 CDC measures the charge transfer
between EXC pin and CIN pin. Any resistance connected in
parallel to the measured capacitance CX (see Figure 38), such as
the parasitic resistance of the sensor, also transfers charge.
Therefore, the parallel resistor is seen as an additional
capacitance in the output data. The equivalent parallel
capacitance (or error caused by the parallel resistance) can be
approximately calculated as
4
1
×
=
EXC
P
F
R
C
Where RP is the parallel resistance and CEXC is the excitation
frequency. See the typical performance characteristics shown in
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相关代理商/技术参数 |
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|---|---|
| AD7745ARUZ-REEL | 功能描述:IC CONV 1CH CAP TO DGTL 16TSSOP RoHS:是 类别:集成电路 (IC) >> 数据采集 - ADCs/DAC - 专用型 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:50 系列:- 类型:数据采集系统（DAS） 分辨率（位）:16 b 采样率（每秒）:21.94k 数据接口:MICROWIRE?，QSPI?，串行，SPI? 电压电源:模拟和数字 电源电压:1.8 V ~ 3.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:40-WFQFN 裸露焊盘 供应商设备封装:40-TQFN-EP（6x6） 包装:托盘 |
| AD7745ARUZ-REEL7 | 功能描述:IC CONV 1CH CAP TO DGTL 16TSSOP RoHS:是 类别:集成电路 (IC) >> 数据采集 - ADCs/DAC - 专用型 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:50 系列:- 类型:数据采集系统（DAS） 分辨率（位）:16 b 采样率（每秒）:21.94k 数据接口:MICROWIRE?，QSPI?，串行，SPI? 电压电源:模拟和数字 电源电压:1.8 V ~ 3.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:40-WFQFN 裸露焊盘 供应商设备封装:40-TQFN-EP（6x6） 包装:托盘 |
| AD7746 | 制造商:AD 制造商全称:Analog Devices 功能描述:24-Bit Capacitance-to-Digital Converter with Temperature Sensor |
| AD7746ARUZ | 功能描述:IC CONV 2CH CAP TO DGTL 16-TSSOP RoHS:是 类别:集成电路 (IC) >> 数据采集 - ADCs/DAC - 专用型 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:50 系列:- 类型:数据采集系统（DAS） 分辨率（位）:16 b 采样率（每秒）:21.94k 数据接口:MICROWIRE?，QSPI?，串行，SPI? 电压电源:模拟和数字 电源电压:1.8 V ~ 3.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:40-WFQFN 裸露焊盘 供应商设备封装:40-TQFN-EP（6x6） 包装:托盘 |
| AD7746ARUZ-REEL | 功能描述:IC CONV 2CH CAP TO DGTL 16-TSSOP RoHS:是 类别:集成电路 (IC) >> 数据采集 - ADCs/DAC - 专用型 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:50 系列:- 类型:数据采集系统（DAS） 分辨率（位）:16 b 采样率（每秒）:21.94k 数据接口:MICROWIRE?，QSPI?，串行，SPI? 电压电源:模拟和数字 电源电压:1.8 V ~ 3.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:40-WFQFN 裸露焊盘 供应商设备封装:40-TQFN-EP（6x6） 包装:托盘 |
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