MB88101A_03 Datasheet, PDF (9/19 Pages) Fujitsu Component Limited. – A/D Converter (With 4-channel Input at 12-bit Resolution)

MB88101A
(3) Definitions of A/D converter terms
• Resolution
Analog transition identifiable by the A/D converter
• Linearity error
Deviation of the straight line drawn between the zero transition point (0000 0000 0000 ↔ 0000 0000 0001)
and the full-scale transition point (1111 1111 1110 ↔ 1111 1111 1111) of the device from actual conversion
characteristics
• Differential linearity error
Deviation from the ideal input voltage required to shift output code by one LSB
Digital output
Actual converted value
1111 1111 1111
1111 1111 1110
•
•
•
•
•
•
•
•
•
0000 0000 0010
0000 0000 0001
0000 0000 0000
VOT
(1 LSB × N + VOT)
Linearity error
VNT V(N+1)T
• 1 LSB
VFST - VOT
=
4094
• Linearity error
VNT - (1 LSB × N + VOT)
=
1 LSB
• Differential linearity error =
V(N+1)T - VNT
1 LSB ^{- 1}
(LSB)
(LSB)
Ideal converted value
Analog output
VFST
• Analog input equivalent circuit
Analog input
RON1
RON2
⋅ RON1 = About 1.5 kΩ
⋅ RON2 = About 1.5 kΩ
⋅ C0 = About 60 pF
Note: The above values are reference values.
Comparator
C0
Notes: • The tolerance of output impedance of an external circuit connected to this A/D converter has an effect on
conversion time (CLK frequency). See “s TYPICAL CHARACTERISTICS”.
• If the output impedance of the external input is too high, the analog voltage sampling time may be short.
• When turning the device on, turn the power supply for the digital system first before turning VREF on.
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