TC1796
Peripheral Units (Vol. 2 of 2)
Analog-to-Digital Converter (ADC)
User’s Manual 25-38 V2.0, 2007-07
ADC, V2.0
25.1.6 Error through Overload Conditions
An additional error can occur when overloading an analog input (such as channel D). In
this case, an additional leakage current exists between the analog input D and the
adjacent analog inputs D ± 1, affecting the conversion result of an analog input channel
D by an additional error AEL based on the additional sampled voltage V
AEL
(Analog Error
Leakage).
V
AEL
|
D
±
1
= R
AIN
|
D
× | I
OV
|
D
× k
A
(25.9)
The coupling factor k
A
determines the physical relation of two adjacent analog inputs.
The resulting error AEL is given by:
(25.10)
where
• V
AREF
: reference voltage for conversion
• R
AIN
|
D
: resistance of the analog input channel D
• I
OV
|
D
: overload current of the analog input D
• AEL: additional error caused by a leakage current, related to V
AREF
•k
A
: coupling factor for the analog input D
Note: If AEL is calculated in bit units, AEL must be multiplied by 2
n
-1.
AEL
D1±
R
AIN
D
I
OV
D
k
A
××
V
AREF
-------------------------------------------------=
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