
ST72C171
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8-BIT ADC CHARACTERISTICS
(Cont’d)
ADC Accuracy
Figure 98. ADC Accuracy Characteristics
Notes:
1. ADC Accuracy vs. Negative Injection Current:
For I
=0.8mA, the typical leakage induced inside the die is 1.6μA and the effect on the ADC accuracy is a loss of 1 LSB
for each 10K
increase of the external analog source impedance. This effect on the ADC accuracy has been observed
under worst-case conditions for injection:
- negative injection
- injection to an Input with analog capability, adjacent to the enabled Analog Input
- at 5V V
DD
supply, and worst case temperature.
3. Data based on characterization results over the whole temperature range, monitored in production.
Symbol
|E
T
|
E
O
E
G
|E
D
|
|E
L
|
Parameter
Conditions
Min
Max
1
0.5
0.5
0.5
0.5
Unit
Total unadjusted error
1)
Offset error
1)
Gain Error
1)
Differential linearity error
1)
Integral linearity error
1)
V
DD
=5.0V,
3)
f
CPU
=8MHz
LSB
-0.5
-0.5
E
O
E
G
1 LSB
IDEAL
1LSBIDEAL
VDDA
VSSA
256
–
=
V
in
(LSB
IDEAL
)
(1) Example of an actual transfer curve
(2) The ideal transfer curve
(3) End point correlation line
E
=Total Unadjusted Error: maximum deviation
between the actual and the ideal transfer curves.
E
=Offset Error: deviation between the first actual
transition and the first ideal one.
E
=Gain Error: deviation between the last ideal
transition and the last actual one.
E
=Differential Linearity Error: maximum deviation
between actual steps and the ideal one.
E
=Integral Linearity Error: maximum deviation
between any actual transition and the end point
correlation line.
Digital Result ADCDR
255
254
253
5
4
3
2
1
0
V
SSA
7
6
1
2
3
4
5
6
7
253 254 255 256
(1)
(2)
E
T
E
D
E
L
(3)
V
DDA