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參數(shù)資料
| 型號： | ISO807 |
| 文件頁數(shù)： | 9/12頁 |
| 文件大?。?/td> | 199K |
| 代理商： | ISO807 |
9
ISO807
±
10V
0-5V
0-4V
FIGURE 3b. Circuit Diagrams (Without Hardware Trim).
SOFTWARE CALIBRATION
To calibrate the offset and gain in software, no external
resistors are required. However, to get the data sheet speci-
fications for offset and gain, the resistors shown in Figure 3b
are necessary. See the
No Calibration
section for more
details on the external resistors. Refer to Table VII for the
range of offset and gain errors with and without the external
resistors.
NO CALIBRATION
See Figure 3b for circuit connections. Note that the actual
voltage dropped across the external resistors is at least two
orders of magnitude lower than the voltage dropped across
the internal resistor divider network. This should be consid-
ered when choosing the accuracy and drift specifications of
the external resistors. In most applications, 1% metal-film
resistors will be sufficient.
The external resistors shown in Figure 3b may not be
necessary in some applications. These resistors provide
compensation for an internal adjustment of the offset and
gain which allows calibration with a single supply. Not
using the external resistors will result in offset and gain
errors in addition to those listed in the electrical specifica-
tions section. Offset refers to the equivalent voltage of the
digital output when converting with the input grounded. A
positive gain error occurs when the equivalent output volt-
age of the digital output is larger than the analog input. Refer
to Table VII for nominal ranges of gain and offset errors
with and without the external resistors. Refer to Figure 4 for
typical shifts in the transfer functions which occur when the
external resistors are removed.
To further analyze the effects of removing any combination
of the external resistors, consider Figure 5. The combination
of the external and the internal resistors form a voltage
divider which reduces the input signal to a 0.3125V to
2.8125V input range at the CDAC. The internal resistors are
laser trimmed to high relative accuracy to meet full specifi-
cations. The actual input impedance of the internal resistor
network looking into pin 12 or pin 14 however, is only
accurate to
±
20% due to process variations. This should be
taken into account when determining the effects of removing
the external resistors.
REFERENCE
The ISO807 operates with its internal 2.5V reference. The
internal reference has approximately an 8ppm/
°
C drift (typi-
cal) and accounts for approximately 20% of the full scale
error (FSE =
±
0.5%).
The ISO807 also has an internal buffer for the reference
voltage. See Figure 6 for characteristic impedances at the
input and output of the buffer with all combinations of
power down and reference down.
REF
REF (pin 16) is an input for an external reference or the
output for the internal 2.5V reference. A 2.2
μ
F tantalum
capacitor should be connected as close as possible to the
REF pin from ground. This capacitor and the output resis-
tance of REF create a low pass filter to bandlimit noise on
the reference. Using a smaller value capacitor will introduce
more noise to the reference, degrading the SNR and SINAD.
The REF pin should not be used to drive external AC or DC
loads. See Figure 6.
The range for the external reference is 2.3V to 2.7V and
determines the actual LSB size. Increasing the reference
voltage will increase the full scale range and the LSB size of
the converter which can improve the SNR.
200
12
14
15
16
17
AGND
REF
CAP
R2
IN
R1
IN
+
+
2.2μF
2.2μF
33.2k
100
V
IN
200
12
14
15
16
17
AGND
REF
CAP
R2
IN
R1
IN
+
+
2.2μF
2.2μF
33.2k
100
V
IN
200
12
14
15
16
17
AGND
REF
CAP
R2
IN
R1
IN
+
+
2.2μF
2.2μF
100
+5V
66.5k
V
IN
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| ISO807 | Isolated 16-Bit Sampling Analog-To-Digital Converter(隔離的16位采樣A\D轉(zhuǎn)換器) |
| ISO808 | Isolated 12-Bit Sampling ANALOG-TO-DIGITAL CONVERTER |
| ISO808P | Isolated 12-Bit Sampling ANALOG-TO-DIGITAL CONVERTER |
| ISO809 | Isolated 16-Bit Sampling ANALOG-TO-DIGITAL CONVERTER |
| ISO809P | Isolated 16-Bit Sampling ANALOG-TO-DIGITAL CONVERTER |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ISO807P | 制造商:BB 制造商全稱:BB 功能描述:Isolated 16-Bit Sampling ANALOG-TO-DIGITAL CONVERTER |
| ISO808 | 制造商:BB 制造商全稱:BB 功能描述:Isolated 12-Bit Sampling ANALOG-TO-DIGITAL CONVERTER |
| ISO808P | 制造商:BB 制造商全稱:BB 功能描述:Isolated 12-Bit Sampling ANALOG-TO-DIGITAL CONVERTER |
| ISO809 | 制造商:BB 制造商全稱:BB 功能描述:Isolated 16-Bit Sampling ANALOG-TO-DIGITAL CONVERTER |
| ISO809P | 制造商:BB 制造商全稱:BB 功能描述:Isolated 16-Bit Sampling ANALOG-TO-DIGITAL CONVERTER |
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