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參數(shù)資料
| 型號： | ADS1203IPWT |
| 英文描述： | S/P 20 RED REV M |
| 中文描述： | 電機控制電流測量 |
| 文件頁數(shù)： | 13/24頁 |
| 文件大小： | 276K |
| 代理商： | ADS1203IPWT |
SBAS318 JUNE 2004
www.ti.com
13
GENERAL DESCRIPTION
The ADS1203 is a single-channel, 2nd-order, CMOS
delta-sigma modulator, designed for medium- to
high-resolution A/D conversions from DC to 39kHz with
an oversampling ratio (OSR) of 256. The output of the
converter (MDAT) provides a stream of digital ones and
zeros. The time average of this serial output is
proportional to the analog input voltage.
The modulator shifts the quantization noise to high
frequencies. A low-pass digital filter should be used at
the output of the delta-sigma modulator. The primary
purpose of the digital filter is to filter out high-frequency
noise. The secondary purpose is to convert the 1-bit
data stream at a high sampling rate into a higher-bit
data word at a lower rate (decimation). A digital signal
processor (DSP), microcontroller (
μ
C), or field
programmable gate array (FPGA) could be used to
implement the digital filter. Figure 5 shows the
ADS1203 connected to a DSP.
The overall performance (speed and accuracy)
depends on the selection of an appropriate OSR and
filter type. A higher OSR produces greater output
accuracy while operating at a lower refresh rate.
Alternatively, a lower OSR produces lower output
accuracy, but operates at a higher refresh rate. This
system allows flexibility with the digital filter design and
is capable of A/D conversion results that have a
dynamic range exceeding 95dB with an OSR = 256.
THEORY OF OPERATION
The differential analog input of the ADS1203 is
implemented with a switched-capacitor circuit. This
circuit implements a 2nd-order modulator stage, which
digitizes the analog input signal into a 1-bit output
stream. The clock source can be internal as well as
external. Different frequencies for this clock allow for a
variety of solutions and signal bandwidths (however,
this can only be used in mode 3). The analog input
signal is continuously sampled by the modulator and
compared to an internal voltage reference. A digital
stream, which accurately represents the analog input
voltage over time, appears at the output of the
converter.
ANALOG INPUT STAGE
Analog Input
The input design topology of the ADS1203 is based on
a fully differential switched-capacitor architecture. This
input stage provides the mechanism to achieve low
system noise, high common-mode rejection (92dB),
and excellent power-supply rejection.
The input impedance of the analog input is dependent
on the modulator clock frequency (f
CLK
), which is also
the sampling frequency of the modulator. Figure 6
shows the basic input structure of the ADS1203. The
relationship between the input impedance of the
ADS1203 and the modulator clock frequency is:
Z
IN
28k
f
CLK
10MHz
The input impedance becomes a consideration in
designs where the source impedance of the input signal
is high. This may cause a degradation in gain, linearity
and THD. The importance of this effect depends on the
desired system performance. There are two restrictions
on the analog input signals, V
IN
+ and V
IN
. If the input
voltage exceeds the range GND – 0.4V to V
DD
+ 0.3V,
the input current must be limited to 10mA because the
input protection diodes on the front end of the converter
will begin to turn on. In addition, the linearity and the
noise performance of the device is ensured only when
the differential analog voltage resides within
±
250mV;
however, the FSR input voltage is
±
320mV.
27
+5V
+5V
27
1nF
1nF
0.1
μ
F
10nF
SPICLK
SPISIMO
V
SSO
V
DD
MCLK
MDAT
GND
M0
V
IN
+
V
IN
M1
ADS1203
DSP
V
DDO
M
Figure 5. Connection Diagram for the ADS1203 Delta-Sigma Modulator Including DSP
(1)
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADS1203IPWTG4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC Current Shunt D-S Modulator RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS1203IRGTR | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC Current Shunt D-S Modulator RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS1203IRGTRG4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC Current Shunt D-S Modulator RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS1203IRGTT | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC Current Shunt D-S Modulator RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| ADS1203IRGTTG4 | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC Current Shunt D-S Modulator RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
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