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ADS8322Y/2K 参数 Datasheet PDF下载

ADS8322Y/2K图片预览
型号: ADS8322Y/2K
PDF下载: 下载PDF文件 查看货源
内容描述: 16位, 500kHz的,微功耗采样模拟数字转换器 [16-Bit, 500kHz, MicroPower Sampling ANALOG-TO-DIGITAL CONVERTER]
分类和应用: 转换器
文件页数/大小: 10 页 / 204 K
品牌: BB [ BURR-BROWN CORPORATION ]
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limited between –0.1V and 0.5V, allowing the input to reject  
small signals which are common to both the +IN and –IN  
inputs. The +IN input has a range of –0.1V to +VA + 0.1V.  
READING DATA  
The ADS8322 outputs full parallel data in Straight Binary  
format, as shown in Table I. The parallel output will be  
active when CS and RD are both LOW. The output data  
should not be read 125ns prior to the falling edge of  
CONVST and 10ns after the falling edge. Any other combi-  
nation of CS and RD will tri-state the parallel output. Refer  
to Table I for ideal output codes.  
The input current on the analog inputs depends upon a  
number of factors: sample rate, input voltage, and source  
impedance. Essentially, the current into the ADS8322 charges  
the internal capacitor array during the sample period. After  
this capacitance has been fully charged, there is no further  
input current. The source of the analog input voltage must be  
able to charge the input capacitance (25pF) to a 16-bit  
settling level within the acquisition time (400ns) of the  
device. When the converter goes into Hold mode, the input  
impedance is greater than 1G.  
DESCRIPTION  
ANALOG VALUE  
2 VREF  
DIGITAL OUTPUT  
STRAIGHT BINARY  
Full-Scale Range  
Least Significant  
Bit (LSB)  
2 VREF/65535  
BINARY CODE  
HEX CODE  
FFFF  
Care must be taken regarding the absolute analog input  
voltage. To maintain the linearity of the converter, the –IN  
input should not drop below GND – 100mV or exceed  
GND + 0.5V. The +IN input should always remain within  
the range of GND – 100mV to VA + 100mV. Outside of  
these ranges, the converter’s linearity may not meet specifi-  
cations. To minimize noise, low-bandwidth input signals  
with lowpass filters should be used.  
+Full Scale  
Midscale  
2VREF 1 LSB  
VREF  
1111 1111 1111 1111  
1000 0000 0000 0000  
0111 1111 1111 1111  
0000 0000 0000 0000  
8000  
Midscale 1LSB  
Zero  
VREF 1 LSB  
0V  
7FFF  
0000  
TABLE I. Ideal Input Voltages and Output Codes.  
BYTE  
The output data will appear as a full 16-bit word on DB15-  
DB0 (MSB-LSB), if BYTE is LOW. The result may also be  
read on an 8-bit bus by using only DB7-DB0. In this case two  
reads are necessary. The first, as before, leaving BYTE LOW  
and reading the 8 least significant bits on DB7-DB0, then  
bringing BYTE HIGH. When BYTE is HIGH, the upper 8 bits  
(D15-D8) will appear on DB7-DB0.  
DIGITAL INTERFACE  
TIMING AND CONTROL  
See the timing diagram in the Timing Characteristics section  
for detailed information on timing signals and their require-  
ment.  
The ADS8322 uses an external clock (CLOCK) which  
controls the conversion rate of the CDAC. With a 10MHz  
external clock, the A/D converter sampling rate is 500kHz,  
which corresponds to a 2µs maximum throughput time.  
NOISE  
Figure 2 shows the transition noise of the ADS8322. A low-  
level DC input was applied to the analog-input pins and the  
converter was put through 8,192 conversions. The digital  
output of the A/D converter will vary in output code due to  
the internal noise of the ADS8322. This is true for all 16-bit  
SAR-type A/D converters. Using a histogram to plot the  
output codes, the distribution should appear bell-shaped  
Conversions are initiated by bringing the CONVST pin  
LOW for a minimum of 20ns (after the 20ns minimum  
requirement has been met, the CONVST pin can be brought  
HIGH), while CS is LOW. The ADS8322 will switch from  
Sample-to-Hold mode on the falling edge of the CONVST  
command. Following the first rising edge of the external  
clock after a CONVST LOW, the ADS8322 will begin  
conversion (this first rising edge of the external clock repre-  
sents the start of clock cycle one; the ADS8322 requires 16  
rising clock edges to complete a conversion). The BUSY  
output will go HIGH immediately following CONVST go-  
ing LOW. BUSY will stay HIGH through the conversion  
process and return LOW when the conversion has ended.  
5052  
1968  
Both RD and CS can be HIGH during and before a conver-  
sion (although CS must be LOW when CONVST goes LOW  
to initiate a conversion). Both the RD and CS pins are  
brought LOW in order to enable the parallel output bus with  
the conversion.  
818  
300  
54  
0014  
0015  
0016  
Code  
0017  
0018  
FIGURE 2. Histogram of 8,192 Conversions of a Low Level  
DC Input.  
ADS8322  
8
SBAS215