mc9s08gt16a Freescale Semiconductor, Inc, mc9s08gt16a Datasheet - Page 232

• Manufacturer Part Number: mc9s08gt16a
• Description: Hcs08 Microcontrollers 8-bit Microcontroller Family
• Manufacturer: Freescale Semiconductor, Inc

Analog-to-Digital Converter (S08ATDV3)
In the case of a 0.1 µF C
However, in the case of repeated conversions at a rate of f
continuous and controlled only by R
This is a worst case sampling error which does not account for R
and C
large C
accuracy specified under the worst case conditions of maximum ∆V
be less than the maximum value of 10 kΩ. The maximum value of 10 kΩ for R
error in the worst case condition of maximum ∆V
14.4.3
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.
14.4.4
Figure 14-11
voltage in millivolts. The vertical axis the conversion result code. The ATD is specified with the following
figures of merit:
232
•
•
•
•
•
+ (∆V
AIN
AS
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
SAMP
during the sample window. It does illustrate that high values of R
is used and sufficient time to recharge C
Analog Input Multiplexer
ATD Module Accuracy Definitions
illustrates an ideal ATD transfer function. The horizontal axis represents the ATD input
/ (V
REFH
E
S
= 2
- V
E
AS
S
N
REFL
= 2
, a worst case sampling error of 0.5 LSB is achieved regardless of R
* (∆V
N
)) * Min[(C
* {(∆V
SAMP
1LSB = (V
MC9S08GT16A/GT8A Data Sheet, Rev. 1
AS
AIN
Q
/ (V
REFL
) — This is the error caused by the division of the perfect ideal
(not R
AIN
/ (V
REFH
/ (C
to V
REFH
REFH
AIN
– V
AIN
REFH
– V
– V
REFL
), and reduces the overall sampling error to:
SAMP
+ C
AS
REFL
REFL
AS
)) * (C
(ATD reference potentials) will result in valid ATD
is provided between samples. In order to achieve
and minimum C
)), e
)) * e
) / 2
SAMP
AIN
−(1 / (f
N
−(1 / (f SAMP * R AS * C AS )
, R
/ (C
ATDCLK
AS
AS
AIN
must re-charge C
recharging the combination of C
SAMP
+ C
* (R
AS
AS
and minimum C
AS
.
))
AS
AS
+ R
(>10 kΩ) are possible if a
is to ensure low sampling
AIN
) * C
Freescale Semiconductor
N
AS
AIN
steps. This error is
. This recharge is
)
]}
AS
, R
AS
Eqn. 14-3
Eqn. 14-4
AS
Eqn. 14-5
.
must
AS