AN2438 Freescale Semiconductor / Motorola, AN2438 Datasheet - Page 5

• Manufacturer Part Number: AN2438
• Description: ADC Definitions and Specifications
• Manufacturer: Freescale Semiconductor / Motorola

Zero-Scale Error and Full-Scale Error
MOTOROLA
NOTE:
NOTE:
The non-linearities at the endpoints are considered special cases due to the
ease with which they are measured and corrected. The non-linearity at the
beginning of the Actual Transfer Function is called the Zero-Scale Error (E
and the non-linearity at the top end of the function is called Full-Scale Error
(E
The Ideal Code Width for the zero code is ½LSB for ADC’s with ½LSB
compensated quantization.
The Ideal Code Width for the last code is 1½LSB for ADC’s with ½LSB
compensated quantization.
FS
•
•
Freescale Semiconductor, Inc.
). The Zero- and Full-Scale Errors have the following definitions:
For More Information On This Product,
(+) Zero-Scale Error
$7
$6
$5
$4
$3
$2
$1
Zero-Scale Error (E
voltage and the ideal first transition voltage (if the first transition is not
from $000 to $001, then use the difference between the actual and ideal
$001–$002 transition voltages, and so on).
Representing this error is by code widths:
Or, in the case where the first “x” codes are missing,
Full-Scale Error (E
transition voltage and the ideal last transition voltage (if the last transition
is not from $3FE to $3FF, then use the difference between the actual
and ideal $3FD–$3FE transition voltages, and so on).
Representing this error by code widths:
Or, in the case where the last “x” codes are missing,
Conversion
Zero- and Full-Scale Error
ADC Definitions and Specifications
E
E
E
E
Ideal Transfer
Input Voltage in LSB
ZS
ZS
FS
FS
Go to: www.freescale.com
Function
= CCW(0) – ICW(0)
= CCW(x) – sum(i=0
= CCW(last) – ICW(last)
= CCW(last-x) – sum(i=x→last)[ICW(i)]
(-) Full-Scale Error
4
Adjusted Transfer
Figure 2. Endpoints Error Graph
5
Function
FS
6
ZS
) is the difference between the actual last
) is the difference between actual first transition
7
V
REFH
→
x)[ICW(i)]
$7
$6
$5
$4
$3
$2
$1
Conversion
(+) Offset Error
Zero-Scale Error and Full-Scale Error
Offset and Gain Error
Straight-Line
Trans Func.
Adjusted
Input Voltage in LSB
Function Plus Offset
4
Ideal S.L. Transfer
5
(+) Gain Error
6
7
V
REFH
AN2438/D
ZS
)
5