CHAPTER 12 A/D CONVERTER
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User’s Manual U14359EJ4V0UM
12.9 How to Read A/D Converter’s Characteristic Table
This section describes the terms related to the A/D converter.
(1) Resolution
The minimum analog input voltage that can be recognized, i.e., the ratio of an analog input voltage to 1 bit of
digital output is called 1 LSB (least significant bit). The ratio of 1 LSB to the full scale is expressed as %FSR
(full-scale range). %FSR is the ratio of a range of convertible analog input voltages expressed in percentage,
and can be expressed as follows, independently of the resolution.
1%FSR = (Maximum value of convertible analog input voltage – Minimum value of convertible analog
input voltage)/100
= (AV
REF
−
0)/100
= AV
REF
/100
Where the resolution is 10 bits, 1 LSB is as follows:
1 LSB = 1/2
10
= 1/1,024
= 0.098%FSR
The accuracy is determined by the total error, independently of the resolution.
(2) Total error
This is the maximum value of difference between an actually measured value and a theoretical value.
It is a total of zero-scale error, full-scale error, linearity error, and errors that occur in combination of these
errors.
The total error in the characteristic table does not include quantization error.
Figure 12-18. Total Error
Ideal line
Total errors
1......1
0......0
0
AV
REF
Analog input
Digital output
