Differential Non-Linearity (DNL)
It is the deviation in code-width from 1LSb (Figure 4). The difference is calculated for each and every transition. The largest difference is reported as DNL. It is important to note that the DNL is measured after the transfer function is normalized to match offset error and gain error. Note that the DNL cannot be any less than -1LSb. In the other direction, DNL can be >1LSb.
Absolute Error
The maximum deviation between any transition point from the corresponding ideal transfer function is defined as the absolute error. This is how it is measured and reported in the PIC16C7X (Figure 5). The notable difference between absolute error and integral non-linearity (INL) is that the measured data is not normalized for full scale and offset errors in absolute error. Absolute Error is probably the first parameter the user will review to evaluate an A/D. Sometimes absolute error is reported as the sum of offset, full-scale and integral non-linearity errors.
Total Unadjusted Error
Total Unadjusted Error is the same as absolute error. Again, sometimes it is reported as the sum of offset, full-scale and integral non-linearity errors.
No Missing Code
No missing code implies that as the analog input voltage is gradually increased from zero to full scale (or vice versa), all digital codes are produced. Stated otherwise, changing analog input voltage from one quantum of the analog range to the next adjacent range will not produce a change in the digital output by more than one code count.
Monotonic
Monotonicity guarantees that an increase (or decrease) in the analog input value will result in an equal or greater digital code (or less). Monotonicity does not guarantee that there are no missing codes. However, it is an important criterion for feedback control systems. Non-monotonicity may cause oscillations in such systems. The first derivative of a monotonic function always has the same sign.
Reference:
It is the deviation in code-width from 1LSb (Figure 4). The difference is calculated for each and every transition. The largest difference is reported as DNL. It is important to note that the DNL is measured after the transfer function is normalized to match offset error and gain error. Note that the DNL cannot be any less than -1LSb. In the other direction, DNL can be >1LSb.
Absolute Error
The maximum deviation between any transition point from the corresponding ideal transfer function is defined as the absolute error. This is how it is measured and reported in the PIC16C7X (Figure 5). The notable difference between absolute error and integral non-linearity (INL) is that the measured data is not normalized for full scale and offset errors in absolute error. Absolute Error is probably the first parameter the user will review to evaluate an A/D. Sometimes absolute error is reported as the sum of offset, full-scale and integral non-linearity errors.
Total Unadjusted Error
Total Unadjusted Error is the same as absolute error. Again, sometimes it is reported as the sum of offset, full-scale and integral non-linearity errors.
No Missing Code
No missing code implies that as the analog input voltage is gradually increased from zero to full scale (or vice versa), all digital codes are produced. Stated otherwise, changing analog input voltage from one quantum of the analog range to the next adjacent range will not produce a change in the digital output by more than one code count.
Monotonic
Monotonicity guarantees that an increase (or decrease) in the analog input value will result in an equal or greater digital code (or less). Monotonicity does not guarantee that there are no missing codes. However, it is an important criterion for feedback control systems. Non-monotonicity may cause oscillations in such systems. The first derivative of a monotonic function always has the same sign.
Reference:
- http://en.wikipedia.org
- AN546, Microchip Technology Inc. Sumit Mitra, Stan D’Souza, and Russ Cooper,
