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ADS1255IDB 参数 Datasheet PDF下载

ADS1255IDB图片预览
型号: ADS1255IDB
PDF下载: 下载PDF文件 查看货源
内容描述: 极低噪声, 24位模拟数字转换器 [Very Low Noise, 24-Bit Analog-to-Digital Converter]
分类和应用: 转换器
文件页数/大小: 39 页 / 422 K
品牌: BB [ BURR-BROWN CORPORATION ]
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ꢐꢕ ꢙꢚ ꢋ ꢛ ꢛ  
ꢐꢕ ꢙꢚ ꢋ ꢛ ꢜ  
www.ti.com  
SBAS288D − JUNE 2003 − REVISED AUGUST 2004  
the digital pins can help by controlling the trace  
impedance. When not using the RESET or SYNC/PDWN  
inputs, tie directly to the ADS1255/6 DVDD pin.  
APPLICATIONS INFORMATION  
GENERAL RECOMMENDATIONS  
The ADS1255 and ADS1256 are very high-resolution A/D  
converters. Getting the optimal performance from them  
requires careful attention to their support circuitry and  
printed circuit board (PCB) design. Figure 25 shows the  
basic connections for the ADS1255. It is recommended to  
use a single ground plane for both the analog and digital  
supplies. This ground plane should be shared with the  
bypass capacitors and analog conditioning circuits.  
However, avoid using this ground plane for noisy digital  
components such as microprocessors. If a split ground  
plane is used with the ADS1255/6, make sure the analog  
and digital planes are tied together. There should not be a  
voltage difference between the ADS1255/6 analog and  
digital ground pins (AGND and DGND).  
Pay special attention to the reference and analog inputs.  
These are the most critical circuits. On the voltage  
reference inputs, bypass with low equivalent series  
resistance (ESR) capacitors. Make these capacitors as  
large as possible to maximize the filtering on the reference.  
With the outstanding performance of the ADS1255/6, it is  
easy for the voltage reference to limit overall performance  
if not carefully selected. When using a stand-alone  
reference, make sure it is very low noise and very low drift.  
Ratiometric measurements, where the input signal and  
reference track each other, are somewhat less sensitive,  
but verify the reference signal is clean.  
Often times, only a simple RC filter (as shown in Figure 25)  
is needed on the inputs. This circuit limits the  
high-frequency noise near the modulator frequency; see  
the Frequency Response section. Avoid low-grade  
dielectrics for the capacitors to minimize temperature  
variations and leakage. Keep the input traces as short as  
possible and place the components close to the input pins.  
When using the ADS1256, make sure to filter all the input  
channels being used.  
As with any precision circuit, use good supply bypassing  
techniques. A smaller value ceramic capacitor in parallel  
with a larger value tantalum or a larger value low-voltage  
ceramic capacitor works well. Place the capacitors, in  
particular the ceramic ones, close to the supply pins. Run  
the digital logic off as low of voltage as possible. This helps  
reduce coupling back to the analog inputs. Avoid ringing  
on the digital inputs. Small resistors (100) in series with  
+5V  
ADS1255  
µ
µ
0.1 F  
10 F  
1
2
3
4
5
6
7
8
9
AVDD  
D1 20  
19  
18  
17  
AGND  
D0/CLKOUT  
SCLK  
49.9  
100  
VREFN  
VREFP  
AINCOM  
AIN0  
µ
µ
47 F  
0.1 F  
100pF  
100pF  
DIN  
2.5V  
100  
100  
49.9  
DOUT 16  
301  
301  
15  
14  
13  
DRDY  
CS  
VINP  
VINN  
µ
0.1 F  
AIN1  
SYNC/PDWN  
RESET  
XTAL1/CLKIN  
18pF  
18pF  
7.68MHz  
XTAL2 12  
DGND 11  
10 DVDD  
+3.3V  
µ
10 F  
µ
0.1 F  
Figure 25. ADS1255 Basic Connections  
28  
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