Datasheet

• The tracking time represents the time between the channel selection change and the time for the controller to
start the AFEC. The AFEC allows a minimum tracking time of 15 AFE clock periods.
•
The conversion time represents the time for the AFEC to convert the analog signal.
The AFE clock frequency is selected in the PRESCAL field of the AFEC_MR. The tracking phase starts during the
conversion of the previous channel. If the tracking time is longer than the conversion time of the12-bit AD converter
(t
CONV
), the tracking phase is extended to the end of the previous conversion.
The AFE clock frequency ranges from f
peripheral clock
/2 if PRESCAL is 1, and f
peripheral clock
/256 if PRESCAL is set to
255 (0xFF). PRESCAL must be programmed to provide the AFE clock frequency given in the section “Electrical
Characteristics”.
The AFE conversion time (t
AFE_conv
) is applicable for all modes and is calculated as follows:

AFE_conv
=
23 × 
AFEClock
When the averager is activated, the AFE conversion time is multiplied by the OSR value.
In Free Run mode, the sampling frequency (f
S
) is calculated as 1/t
AFE_conv
.
Figure 52-2. Sequence of AFE Conversions when T
racking Time > Conversion Time
SAM E70/S70/V70/V71 Family
Analog Front-End Controller (AFEC)
© 2019 Microchip T
echnology Inc.
Datasheet
DS60001527D-page 1656