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ADS1112IDGSR 参数 Datasheet PDF下载

ADS1112IDGSR图片预览
型号: ADS1112IDGSR
PDF下载: 下载PDF文件 查看货源
内容描述: 16位模拟数字转换器与输入多路复用器和板载参考 [16-Bit Analog-to-Digital Converter with Input Multiplexer and Onboard Reference]
分类和应用: 转换器复用器光电二极管PC
文件页数/大小: 18 页 / 680 K
品牌: BB [ BURR-BROWN CORPORATION ]
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ꢉꢃ ꢠꢡꢡꢡ ꢢ  
www.ti.com  
SBAS282D − JUNE 2003 − REVISED MARCH 2004  
TYPICAL CHARACTERISTICS (continued)  
At T = 25°C and VDD = 5V, unless otherwise noted.  
A
THEORY OF OPERATION  
The ADS1112 is a 16-bit, self-calibrating, delta-sigma A/D  
converter with an input multiplexer. Extremely easy to de-  
sign with and configure, the ADS1112 allows precise mea-  
surements to be obtained with a minimum of effort.  
The onboard reference specifications are part of the over-  
all gain and drift specifications of the ADS1112. The con-  
verter drift and gain error specifications reflect the perfor-  
mance of the onboard reference as well as the  
performance of the A/D converter core. There are no sepa-  
rate specifications for the onboard reference itself.  
The ADS1112 consists of a delta-sigma A/D converter  
core with adjustable gain, a 2.048V reference, a clock os-  
cillator, and an I2C interface. Each of these blocks are de-  
scribed in detail in the sections that follow.  
OUTPUT CODE CALCULATION  
The output code is a scaled value that is proportional, ex-  
cept for clipping, to the voltage difference between the two  
analog inputs. The output code is confined to a finite range  
of numbers; this range depends on the number of bits  
needed to represent the code. The number of bits needed  
to represent the output code for the ADS1112 depends on  
the data rate, as shown in Table 1.  
ANALOG-TO-DIGITAL CONVERTER  
The ADS1112 A/D converter core consists of a differential  
switched-capacitor delta-sigma modulator followed by a  
digital filter. The modulator measures the voltage differ-  
ence between the positive and negative analog inputs se-  
lected by the input multiplexer and compares it to a refer-  
ence voltage, which, in the ADS1112, is 2.048V. The digital  
filter receives a high-speed bitstream from the modulator  
and outputs a code, which is a number proportional to the  
input voltage.  
NUMBER OF  
BITS  
MINIMUM  
CODE  
MAXIMUM  
CODE  
DATA RATE  
15SPS  
16  
15  
14  
12  
−32,768  
−16,384  
−8192  
32,767  
16,383  
8191  
30SPS  
60SPS  
MULTIPLEXER  
240SPS  
−2048  
2047  
The ADS1112 has an input multiplexer that provides for  
two differential or three single-ended input channels. Two  
bits in the configuration register control the multiplexer  
setting.  
Table 1. Minimum and Maximum Codes  
For a minimum output code of Min Code, gain setting of the  
PGA, and positive and negative input voltages of VIN+ and  
VIN−, the output code is given by the expression:  
VOLTAGE REFERENCE  
(VIN)) * (VIN*  
)
The ADS1112 contains an onboard 2.048V voltage refer-  
ence. This reference is always used as the ADC voltage  
reference; an external reference cannot be connected.  
The ADS1112 voltage reference is internal only, and can-  
not be measured directly or used by external circuitry.  
Output Code + −1   Min Code   PGA   
2.048V  
In the previous expression, it is important to note that the  
negated minimum output code is used. The ADS1112  
outputs codes in binary two’s complement format, so the  
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