MC9S08GT16 MOTOROLA [Motorola, Inc], MC9S08GT16 Datasheet - Page 226

• Manufacturer Part Number: MC9S08GT16
• Description: Microcontrollers
• Manufacturer: MOTOROLA [Motorola, Inc]

Analog-to-Digital Converter (ATD) Module
14.3.3
The analog input multiplexer selects one of the eight external analog input channels to generate an analog
sample. The analog input multiplexer includes negative stress protection circuitry which prevents
cross-talk between channels when the applied input potentials are within specification. Only analog input
signals within the potential range of V
conversions.
14.3.4
Figure 14-4
voltage in millivolts. The vertical axis the conversion result code. The ATD is specified with the following
figures of merit:
226
•
•
•
•
•
•
Number of bits (N) — The number of bits in the digitized output
Resolution (LSB) — The resolution of the ATD is the step size of the ideal transfer function. This
is also referred to as the ideal code width, or the difference between the transition voltages to a
given code and to the next code. This unit, known as 1LSB, is equal to
Inherent quantization error (E
straight-line transfer function into the quantized ideal transfer function with 2
± 1/2 LSB.
Differential non-linearity (DNL) — This is the difference between the current code width and the
ideal code width (1LSB). The current code width is the difference in the transition voltages to the
current code and to the next code. A negative DNL means the transfer function spends less time at
the current code than ideal; a positive DNL, more. The DNL cannot be less than –1.0; a DNL of
greater than 1.0 reduces the effective number of bits by 1.
Integral non-linearity (INL) — This is the difference between the transition voltage to the current
code and the transition to the corresponding code on the adjusted transfer curve. INL is a measure
of how straight the line is (how far it deviates from a straight line). The adjusted ideal transition
voltage is:
Zero scale error (E
and the ideal transition to that code. Normally, it is defined as the difference between the actual and
ideal transition to code $001, but in some cases the first transition may be to a higher code. The
ideal transition to any code is:
Adjusted Ideal Trans. V =
Analog Input Multiplexer
ATD Module Accuracy Definitions
illustrates an ideal ATD transfer function. The horizontal axis represents the ATD input
Ideal Transition V =
ZS
) — This is the difference between the transition voltage to the first valid code
1LSB = (V
MC9S08GB/GT Data Sheet, Rev. 2.3
Q
(Current Code - 1/2)
REFL
) — This is the error caused by the division of the perfect ideal
(Current Code - 1/2)
to V
REFH
2
REFH
N
– V
2
REFL
N
(ATD reference potentials) will result in valid ATD
) / 2
* ((V
N
REFH
*(V
REFH
+ E
FS
– V
) - (V
REFL
REFL
)
Freescale Semiconductor
N
steps. This error is
+ E
ZS
))
Eqn. 14-5
Eqn. 14-6
Eqn. 14-7