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LSB Sizes for Each Analog Input Range in AD7328

Question asked by kutti on Jun 4, 2015
Latest reply on Jun 14, 2015 by jcolao


I am using a AD7328 and in the Data sheet page 16  table 7 it is mentioned as below:

Input RangeFull Scale Range/8192 codesLSB Size
+/-10V20 V2.441 mv
+/-5V10 V1.22 mv
+/-2.5V5 V0.61 mv
0V to +10V10 V1.22 mv


The confusion is for first 3 entries. The LSB size does not seems right. As we are using the bi polar input,

bit 13 is used as sign bit so effective bits available for conversion is only 12 bits. Considering this,

2^12 = 4096.

So LSB size will be:

20/4096 = 4.882 mv

10/4096 = 2.44 mv

5/4096 =  1.22 mv

Please let me know if you have any other observation on this.@