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Definitions of a/d converter terms – FUJITSU MB91460 SERIES FR60 User Manual

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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

=

V

FST

- V

OT

[V]

1022

V

OT

: Voltage at which digital output transit from (000)

H

to (001)

H

VV

FST

: Voltage at which digital output transit from (3FE)

H

to (3FF)

H

Digital output N

Linearity error

=

V

NT

- {1LSB

× (N-1) + V

OT

}

[LSB]

1LSB

Digital output N

Differential linearity

error

=

V

(N+1)T

- V

NT

-1

[LSB]

1LSB

V

NT

: 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

V

NT

(Measurement

value)

{1LSB (N- 1)+V

OT

}

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

V

NT

AVss

V

FST

2

V

NT

AVss

(Measurement

value)

AVRH

Digital output

Analog input

Differentional linearity error