MITSUBISHI MICROCOMPUTERS
M37274EFSP
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER
and ON-SCREEN DISPLAY CONTROLLER
• Differential non-linearity error
(8) Definition of A-D Conversion Accuracy
The definition of A-D conversion accuracy is described below.
The deviation of the input voltage required to change output data
by “1,” from the corresponding ideal A-D conversion characteris-
tics between 0 and VREF.
1
Relative accuracy
• Zero transition error (V0T)
The deviation of the input voltage at which A-D conversion output
data changes from “0” to “1,” from the corresponding ideal A-D
conversion characteristics between 0 and VREF.
(Vn+1– Vn) – 1LSB
=
[
]
LSB
Differential non-linearity error
1LSB
2
Absolute accuracy
•
Absolute accuracy error
(V0 – 1/2✕VREF/256)
=
The deviation of the actual A-D conversion characteristics, from the
ideal A-D conversion characteristics between 0 and VREF.
V0T
[
]
LSB
1LSB
Full-scale transition error (VFST)
•
–
✕
+
The deviation of the input voltage at which A-D conversion output
data changes from “255” to “254,” from the corresponding ideal A-
D conversion characteristics between 0 and VREF.
Vn 1LSBA (n 1/2)
[
]
=
LSB
Absolute accuracy error
1LSBA
–
–
(VREF 3/2 VREF/256) V254
✕
[
]
=
VFST
LSB
Note: The analog input voltage “Vn” at which A-D conversion output
1LSB
+
data changes from “n” to “n 1” (n ; 0 to 254) is as follows
(refer to Figure 30) :
Non-linearity error
•
The deviation of the actual A-D conversion characteristics, from the
ideal A-D conversion characteristics between V0 and V254.
V254 V0
–
=
[
[
]
]
V
V
1LSB with respect to relative accuracy
254
+
Vn – (1LSB✕n V0)
VREF
256
[
]
LSB
Non-linearity error
=
=
1LSBA with respect to absolute accuracy
1LSB
Output
data
255
254
Full-scale transition error
(VFST
)
3
2
Differential non-
linearity error
LSB
A
1LSB
n+1
n
Actual A-D
conversion
Non-linearity error
Absolute accuracy
characteristics
A
1LSB
1
2
Ideal A-D conversion characteristics
between V and V254
A
LSB
0
1LSB
Analog input
voltage ( )
V
0
V
0
V
1
V
n
V
n+1
V
254
VREF
Zero transition error (V0T
)
Fig. 30. Definition of A-D Conversion Accuracy
36
RENESAS [ RENESAS TECHNOLOGY CORP ]
