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Chapter 44 A/D Converter

7.Caution

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 =VFST - VOT [V]

1022

VOT : Voltage at which digital output transit from (000)H to (001)H
VVFST: Voltage at which digital output transit from (3FE)H to (3FF)H

Digital output N

Linearity error =VNT - {1LSB× (N-1) + VOT}[LSB]

1LSB

Digital output N

Differentiallinearity

error

=V(N+1)T - VNT -1 [LSB]

1LSB

VNT: Voltage at which digital output transit from (N+1) to N

3FF
3FE
3FD
004
003
002
001
V
OT(Measurement value)
Ideal characteristics
Actual conversion characteristics
VNT
(Measurement
value)
{1LSB (N-1)+VOT}
AVss AVRH
Digital output
Analog input
Linearity error
V
FST
(Measurement
value)
-
Actual conversion characteristics
N+1
N
N-1
N-2
Actual conversion characteristics
Actual conversion characteristics
VNT
AVss
VFST
2
VNT
AVss
(Measurement
value)
AVRH
Digital output
Analog input
Differentional linearity error