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| 型号： | AD7711ANZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 10/28页 |
| 文件大小： | 0K |
| 描述： | IC ADC 24BIT RTD I SOURCE 24-DIP |
| 标准包装： | 15 |
| 位数： | 24 |
| 采样率（每秒）： | 1.03k |
| 数据接口： | 串行 |
| 转换器数目： | 1 |
| 功率耗散（最大）： | 52.5mW |
| 电压电源： | 模拟和数字，双 ± |
| 工作温度： | -40°C ~ 80°C |
| 安装类型： | 通孔 |
| 封装/外壳： | 24-DIP（0.300"，7.62mm） |
| 供应商设备封装： | 24-PDIP |
| 包装： | 管件 |
| 输入数目和类型： | 1 个单端，单极；1 个单端，双极；1 个差分，单极；1 个差分，双极 |
| 产品目录页面： | 778 (CN2011-ZH PDF) |
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REV. G
–18–
AD7711
System calibration can also be used to remove any errors from
an antialiasing filter on the analog input. A simple R, C anti-
aliasing filter on the front end may introduce a gain error on the
analog input voltage, but the system calibration can be used to
remove this error.
System Offset Calibration
System offset calibration is a variation of both the system cali-
bration and self-calibration. In this case, the zero-scale point
for the system is presented to the AIN input of the converter.
System offset calibration is initiated by writing 1, 0, 0 to MD2,
MD1, MD0. The system zero-scale coefficient is determined by
converting the voltage applied to the AIN input, while the full-
scale coefficient is determined from the span between this AIN
conversion and a conversion on VREF. The zero-scale point
should be applied to the AIN input for the duration of the cali-
bration sequence. This is a one-step calibration sequence with
DRDY going low when the sequence is completed. In unipolar
mode, the system offset calibration is performed between the
two endpoints of the transfer function; in bipolar mode, it is
performed between midscale and positive full scale.
Background Calibration
The AD7711 also offers a background calibration mode where
the part interleaves its calibration procedure with its normal
conversion sequence. In the background calibration mode, the
same voltages are used as the calibration points that are used in
the self-calibration mode, that is, shorted inputs and VREF. The
background calibration mode is invoked by writing 1, 0, 1 to
MD2, MD1, MD0 of the control register. When invoked, the
background calibration mode reduces the output data rate of the
AD7711 by a factor of 6 while the –3 dB bandwidth remains
unchanged. The advantage is that the part is continually per-
forming calibration and automatically updating its calibration
coefficients. As a result, the effects of temperature drift, sup-
ply sensitivity, and time drift on zero- and full-scale errors are
automatically removed. When the background calibration mode
is turned on, the part will remain in this mode until Bits MD2,
MD1, and MD0 of the control register are changed. With back-
ground calibration mode on, the first result from the AD7711
will be incorrect because the full-scale calibration will not have
been performed. For a step change on the input, the second
output update will have settled to 100% of the final value.
Table VI summarizes the calibration modes and the calibration
points associated with them. It also gives the duration from
when the calibration is invoked to when valid data is available
to the user.
Table VI. Calibration Truth Table
Cal Type
MD2, MD1, MD0
Zero-Scale Cal
Full-Scale Cal
Sequence
Duration
Self-Cal
0, 0, 1
Shorted Inputs
VREF
One-Step
9
1/Output Rate
System Cal
0, 1, 0
AIN
Two-Step
4
1/Output Rate
System Cal
0, 1, 1
AIN
Two-Step
4
1/Output Rate
System Offset Cal
1, 0, 0
AIN
VREF
One-Step
9
1/Output Rate
Background Cal
1, 0, 1
Shorted Inputs
VREF
One-Step
6
1/Output Rate
Span and Offset Limits
Whenever a system calibration mode is used, there are limits on
the amount of offset and span that can be accommodated. The
range of input span in both the unipolar and bipolar modes has a
minimum value of 0.8
VREF/GAIN and a maximum value of
2.1
VREF/GAIN.
The amount of offset that can be accommodated depends on
whether the unipolar or bipolar mode is being used. This offset
range is limited by the requirement that the positive full-scale
calibration limit is
1.05 VREF/GAIN. Therefore, the offset
range plus the span range cannot exceed 1.05
VREF/GAIN. If
the span is at its minimum (0.8
VREF/GAIN), the maximum
the offset can be is (0.25
VREF/GAIN).
In bipolar mode, the system offset calibration range is again
restricted by the span range. The span range of the converter in
bipolar mode is equidistant around the voltage used for the zero-
scale point; thus the offset range plus half the span range cannot
exceed (1.05
VREF/GAIN). If the span is set to 2 VREF/GAIN,
the offset span cannot move more than
±(0.05 VREF/GAIN)
before the endpoints of the transfer function exceed the input
overrange limits
±(1.05 VREF/GAIN). If the span range is set to
the minimum
±(0.4 VREF/GAIN), the maximum allowable
offset range is
±(0.65 VREF/GAIN).
POWER-UP AND CALIBRATION
On power-up, the AD7711 performs an internal reset that sets
the contents of the control register to a known state. However, to
ensure correct calibration for the device, a calibration routine
should be performed after power-up.
The power dissipation and temperature drift of the AD7711
are low, and no warm-up time is required before the initial
calibration is performed. However, if an external reference is
being used, this reference must have stabilized before calibra-
tion is initiated.
Drift Considerations
The AD7711 uses chopper stabilization techniques to minimize
input offset drift. Charge injection in the analog switches and dc
leakage currents at the sampling node are the primary sources of
offset voltage drift in the converter. The dc input leakage current is
essentially independent of the selected gain. Gain drift within the
converter depends primarily upon the temperature tracking of the
internal capacitors. It is not affected by leakage currents.
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相关代理商/技术参数 |
参数描述 |
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| AD7711ANZ | 制造商:Analog Devices 功能描述:IC ADC 24-BIT SIGMA DELTA |
| AD7711AQ | 功能描述:IC ADC 24BIT RTD I SOURCE 24CDIP RoHS:否 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 |
| AD7711AR | 功能描述:IC ADC 24BIT RTD I SOURCE 24SOIC RoHS:否 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 |
| AD7711AR-REEL | 功能描述:IC ADC 24BIT RTD I SOURCE 24SOIC RoHS:否 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 |
| AD7711AR-REEL7 | 功能描述:IC ADC 24BIT RTD I SOURCE 24SOIC RoHS:否 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 |
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