Device Architecture
Terminology
BW – Bandwidth
BW is a range of frequencies that a Channel can handle.
Channel
A channel is define as an analog input configured as one of the Prescaler range shown in
Table 2-54 on page 2-128. The channel includes the Prescaler circuit and the ADC.
Channel Gain
Channel Gain is a measured of the deviation of the actual slope from the ideal slope. The slope is
measured from the 20% and 80% point.
Gainactual
Gain = -----------------------
Gainideal
EQ 2-1
Channel Gain Error
Channel Gain Error is a deviation from the ideal slope of the transfer function. The Prescaler Gain
Error is expressed as the percent difference between the actual and ideal, as shown in EQ 2-2.
ErrorGain = (1-Gain) × 100%
EQ 2-2
Channel Input Offset Error
Channel Offset error is measured as the input voltage that causes the transition from zero to a
count of one. An Ideal Prescaler will have offset equal to ½ of LSB voltage. Offset error is a positive
or negative when the first transition point is higher or lower than ideal. Offset error is expressed in
LSB or input voltage.
Total Channel Error
Total Channel Error is defined as the total error measured compared to the ideal value. Total
Channel Error is the sum of gain error and offset error combined. Figure 2-68 shows how Total
Channel Error is measured.
Total Channel Error is defined as the difference between the actual ADC output and ideal ADC
output. In the example shown in Figure 2-68, the Total Channel Error would be a negative number.
Channel Gain
Actual Output
Ideal Output
Total Channel Error
Channel Input
Offset Error
Input Voltage to Prescaler
Figure 2-68 • Total Channel Error Example
2-88
Preliminary v1.7
ACTEL [ Actel Corporation ]
