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参数资料
| 型号： | ADS1217 |
| 英文描述： | 8-Channel, 24-Bit ANALOG-TO-DIGITAL CONVERTER |
| 中文描述： | 8通道，24位模拟数字转换器 |
| 文件页数： | 24/28页 |
| 文件大小： | 458K |
| 代理商： | ADS1217 |
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ADS1217
SBAS260B
24
www.ti.com
Filter Selection
—
the ADS1217 uses a (sinx/x) filter or sinc
filter. There are three different sinc filters that can be se-
lected. A fast settling filter will settle in one t
DATA
cycle. The
sinc
2
filter will settle in two cycles and have lower noise. The
sinc
3
will achieve lowest noise and higher number of effective
bits, but requires three cycles to settle. The ADS1217 will
operate with any one of these filters, or it can operate in an
auto mode, where it will first select the fast settling filter after
a new channel is selected and will then switch to sinc
2
for one
reading, followed by sinc
3
from then on.
f
DATA
—
the frequency of the digital output data produced by
the ADS1217, f
DATA
is also referred to as the Data Rate.
f
f
DecimationRatio
f
mfactor DecimationRatio
DATA
MOD
OSC
=
=
f
MOD
—
the frequency or speed at which the modulator of the
ADS1217 is running. This depends on the SPEED bit as
shown below:
DEFINITION OF TERMS
Analog Input Voltage
—
the voltage at any one analog input
relative to AGND.
Analog Input Differential Voltage
—
given by the following
equation: (A
IN+
)
–
(A
IN
–
)
.
Thus, a positive digital output is
produced whenever the analog input differential voltage is
positive, while a negative digital output is produced whenever
the differential is negative.
For example, when the converter is configured with a 2.5V
reference and placed in a gain setting of 1, the positive
full-scale output is produced when the analog input differen-
tial is 2
2.5V. The negative full-scale output is produced
when the differential is 2
(
–
2.5V). In each case, the actual
input voltages must remain within the AGND to AV
DD
range.
Conversion Cycle
—
the term conversion cycleusually refers
to a discrete A/D conversion operation, such as that per-
formed by a successive approximation converter. As used
here, a conversion cycle refers to the t
DATA
time period.
However, each digital output is actually based on the modu-
lator results from several t
DATA
time periods.
FILTER SETTING
MODULATOR RESULTS
Fast Settling
1 t
DATA
Time Period
2 t
DATA
Time Period
3 t
DATA
Time Period
Sinc
2
Sinc
3
BITS rms
BIPOLAR Vrms
UNIPOLAR Vrms
24
22
20
18
16
14
12
596nV
2.38
μ
V
9.54
μ
V
38.1
μ
V
153
μ
V
610
μ
V
2.44mV
298nV
1.19
μ
V
4.77
μ
V
19.1
μ
V
76.4
μ
V
305
μ
V
1.22mV
Data Rate
—
the rate at which conversions are completed.
See definition for f
DATA
.
Decimation Ratio
—
defines the ratio between the output of
the modulator and the output Data Rate. Valid values for the
Decimation Ratio are from 20 to 2047. Larger Decimation
Ratios will have lower noise.
Effective Resolution
—
the effective resolution of the
ADS1217 in a particular configuration can be expressed in
two different units: bits rms (referenced to output) and Vrms
(referenced to input). Computed directly from the converter
’
s
output data, each is a statistical calculation. The conversion
from one to the other is shown below.
Effective number of bits(ENOB) or effective resolutionis
commonly used to define the usable resolution of the
A/D converter. It is calculated from empirical data taken
directly from the device. It is typically determined by applying
a fixed known signal source to the analog input and comput-
ing the standard deviation of the data sample set. The rms
noise defines the
±
σ
interval about the sample mean.
The data from the A/D converter is output as codes, which
then can be easily converted to other units, such as ppm or
volts. The equations and table below show the relationship
between bits or codes, ppm, and volts.
ENOB
ppm
=
–
log(
.
6 02
)
20
SPEED BIT
f
MOD
f
OSC
/128
f
OSC
/256
0
1
f
OSC
—
the frequency of the crystal input signal at the X
IN
input
of the ADS1217.
f
SAMP
—
the frequency, or switching speed, of the input sam-
pling capacitor. The value is given by one of the following
equations:
PGA SETTING
SAMPLING FREQUENCY
1, 2, 4, 8
8
16
32
64, 128
f
f
mfactor
SAMP
OSC
=
f
f
mfactor
SAMP
OSC
=
2
f
f
mfactor
SAMP
OSC
=
8
f
f
mfactor
SAMP
OSC
=
16
f
f
mfactor
SAMP
OSC
=
16
4
PGA
.
10
6 02
20
V
REF
ENOB
2
PGA
.
10
6 02
20
V
REF
ENOB
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ADS1217EVM | 功能描述:数据转换 IC 开发工具 ADS1217 Eval Mod RoHS:否 制造商:Texas Instruments 产品:Demonstration Kits 类型:ADC 工具用于评估:ADS130E08 接口类型:SPI 工作电源电压:- 6 V to + 6 V |
| ADS1217IPFB | 制造商:Texas Instruments 功能描述:IC 24BIT ADC SMD 1217 TQFP48 制造商:Texas Instruments 功能描述:IC, 24BIT ADC, SMD, 1217, TQFP48 |
| ADS1217IPFB | 制造商:Texas Instruments 功能描述:IC 24BIT ADC SMD 1217 TQFP48 |
| ADS1217IPFBR | 功能描述:模数转换器 - ADC 8-Ch 24-Bit ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| ADS1217IPFBRG4 | 功能描述:模数转换器 - ADC 8-Ch 24B ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
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