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■ Definitions of A/D Converter Terms
• Resolution
Analog change identifiable to an A/D converter.
• Linearity error
Deviation between the straight line connecting zero transition point
(00 0000 0000 <- -> 00 0000 0001) and full-scale transition point
(11 1111 1110 <- -> 11 1111 1111) from actual conversion characteristics
• Differential linearity error
Deviation of the input voltage required for changing the output by one LSB, from its ideal value
1LSB
V
: Voltage at which digital output transit from (000)
OT
VV
: Voltage at which digital output transit from (3FE)
FST
Digital output N
Linearity error
Digital output N
Differential linearity
error
V
: Voltage at which digital output transit from (N+1) to N
NT
3FF
3FE
{1LSB (N- 1)+V
-
3FD
004
003
002
001
V
(Measurement value)
OT
AVss
V
- V
FST
OT
=
1022
- {1LSB × (N-1) + V
V
NT
=
1LSB
V
- V
(N+1)T
=
1LSB
Linearity error
Actual conversion characteristics
}
OT
V
FST
(Measurement
value)
V
NT
(Measurement
value)
Actual conversion characteristics
Ideal characteristics
Analog input
[V]
to (001)
H
H
to (3FF)
H
H
}
OT
NT
-1
N+1
N
N-1
N-2
2
AVss
AVss
AVRH
Chapter 44 A/D Converter
[LSB]
[LSB]
Differentional linearity error
Actual conversion characteristics
V
FST
(Measurement
value)
V
V
NT
NT
Actual conversion characteristics
Analog input
7.Caution
AVRH
907
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