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5962-8850501RA 参数 Datasheet PDF下载

5962-8850501RA图片预览
型号: 5962-8850501RA
PDF下载: 下载PDF文件 查看货源
内容描述: 10位A / D转换器 [10-Bit A/D Converter]
分类和应用: 转换器模数转换器
文件页数/大小: 10 页 / 593 K
品牌: ADI [ ADI ]
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AD573  
Figure 4a shows how the converter zero may be offset by up to  
±3 bits to correct the device initial offset and/or input signal  
offsets. As shown, the circuit gives approximately symmetrical  
adjustment in unipolar mode.  
20  
19  
18  
17  
16  
15  
14  
13  
12  
11  
LSB DB0  
DB1  
1
2
PIN 1  
IDENTIFIER  
HBE  
LBE  
DB2  
DR  
3
DIG COM  
BIP OFF  
DB3  
4
DB4  
5
AD573  
TOP VIEW  
(Not to Scale)  
DB5  
ANALOG COM  
ANALOG IN  
6
DB6  
7
8
V–  
DB7  
DB8  
CONVERT  
9
10  
V+  
MSB DB9  
Figure 2. AD573 Pin Connections  
Full-Scale Calibration  
The 5 kthin-film input resistor is laser trimmed to produce a  
current which matches the full-scale current of the internal  
DAC—plus about 0.3%—when an analog input voltage of 9.990  
volts (10 volts – 1 LSB) is applied at the input. The input resis-  
tor is trimmed in this way so that if a fine trimming potentiom-  
eter is inserted in series with the input signal, the input current  
at the full-scale input voltage can be trimmed down to match  
the DAC full-scale current as precisely as desired. However, for  
many applications the nominal 9.99 volt full scale can be  
achieved to sufficient accuracy by simply inserting a 15 resis-  
tor in series with the analog input to Pin 14. Typical full-scale  
calibration error will then be within ±2 LSB or ±0.2%. If more  
precise calibration is desired, a 50 trimmer should be used  
instead. Set the analog input at 9.990 volts, and set the trimmer  
so that the output code is just at the transition between  
11111111 10 and 11111111 11. Each LSB will then have a  
weight of 9.766 mV. If a nominal full scale of 10.24 volts is de-  
sired (which makes the LSB have a weight of exactly 10.00 mV),  
a 100 resistor and a 100 trimmer (or a 200 trimmer with  
good resolution) should be used. Of course, larger full-scale  
ranges can be arranged by using a larger input resistor, but lin-  
earity and full-scale temperature coefficient may be compro-  
mised if the external resistor becomes a sizeable percentage of  
5 k. Figure 3 illustrates the connections required for full-scale  
calibration.  
Figure 4a.  
Figure 4. Offset Trims  
Figure 4b.  
Figure 5 shows the nominal transfer curve near zero for an  
AD573 in unipolar mode. The code transitions are at the edges  
of the nominal bit weights. In some applications it will be pref-  
erable to offset the code transitions so that they fall between the  
nominal bit weights, as shown in the offset characteristics.  
Figure 5. AD573 Transfer Curve—Unipolar Operation  
(Approximate Bit Weights Shown for Illustration, Nominal  
Bit Weights ~ 9.766 mV)  
This offset can easily be accomplished as shown in Figure 4b. At  
balance (after a conversion) approximately 2 mA flows into the  
Analog Common terminal. A 2.7 resistor in series with this  
terminal will result in approximately the desired 1/2 bit offset of  
the transfer characteristics. The nominal 2 mA Analog Common  
current is not closely controlled in manufacture. If high accu-  
racy is required, a 5 potentiometer (connected as a rheostat)  
can be used as R1. Additional negative offset range may be ob-  
tained by using larger values of R1. Of course, if the zero transi-  
tion point is changed, the full-scale transition point will also  
move. Thus, if an offset of 1/2 LSB is introduced, full-scale  
trimming as described on the previous page should be done with  
an analog input of 9.985 volts.  
NOTE: During a conversion, transient currents from the Analog  
Common terminal will disturb the offset voltage. Capacitive  
decoupling should not be used around the offset network. These  
transients will settle appropriately during a conversion. Capaci-  
tive decoupling will “pump up” and fail to settle resulting in  
conversion errors. Power supply decoupling, which returns to  
analog signal common, should go to the signal input side of the  
resistive offset network.  
Figure 3. Standard AD573 Connections  
Unipolar Offset Calibration  
Since the Unipolar Offset is less than ±1 LSB for all versions of  
the AD573, most applications will not require trimming. Figure  
4 illustrates two trimming methods which can be used if greater  
accuracy is necessary.  
REV. B  
–4–