Datasheet

CHAPTER 9 A/D CONVERTER ( μ PD78F920x ONLY)
User’s Manual U18172EJ3V0UD
168
9.4.2 Input voltage and conversion results
The relationship between the analog input voltage input to the analog input pins (ANI0 to ANI3) and the theoretical
A/D conversion result (stored in the 10-bit A/D conversion result register (ADCR)) is shown by the following
expression.
ADCR = INT ( × 1024 + 0.5)
or
(ADCR − 0.5) × ≤ V
AIN < (ADCR + 0.5) ×
where, INT( ): Function which returns integer part of value in parentheses
V
AIN: Analog input voltage
VDD: VDD pin voltage
ADCR: 10-bit A/D conversion result register (ADCR) value
Figure 9-11 shows the relationship between the analog input voltage and the A/D conversion result.
Figure 9-11. Relationship Between Analog Input Voltage and A/D Conversion Result
1023
1022
1021
3
2
1
0
03FFH
03FEH
03FDH
0003H
0002H
0001H
0000H
A/D conversion result
SAR ADCR
1
2048
1
1024
3
2048
2
1024
5
2048
Input voltage/V
DD
3
1024
2043
2048
1022
1024
2045
2048
1023
1024
2047
2048
1
V
AIN
V
DD
VDD
1024
VDD
1024