How To Read A/D Converter Characteristics Table; Overall Error - NEC V850/SB1 User Manual

11.7 How to Read A/D Converter Characteristics Table

Here, special terms unique to the A/D converter are explained.
(1) Resolution
This is the minimum analog input voltage that can be identified. That is, the percentage of the analog input
voltage per bit of digital output is called 1LSB (Least Significant Bit). The percentage of 1LSB with respect to
the full scale is expressed by %FSR (Full Scale Range). %FSR indicates the ratio of analog input voltage
that can be converted as a percentage, and is always represented by the following formula regardless of the
resolution.
1%FSR = (Max. value of analog input voltage that can be converted − Min. value of analog input voltage that
can be converted)/100
= (AV – 0)/100
REF
= AV /100
REF
1LSB is as follows when the resolution is 10 bits.
10
1LSB = 1/2 = 1/1024
= 0.098%FSR
Accuracy has no relation to resolution, but is determined by overall error.

(2) Overall error

This shows the maximum error value between the actual measured value and the theoretical value.
Zero-scale error, full-scale error, linearity error and errors that are combinations of these express the overall
error.
Note that the quantization error is not included in the overall error in the characteristics table.
CHAPTER 11 A/D CONVERTER
Figure 11-9. Overall Error
1 ...... 1
Ideal line
0 ...... 0
0
Analog input
User's Manual U13850EJ6V0UD
Overall
error
AV
REF
447