Datasheet

where:
•
f
S
is the sampling frequency of the AFE channel
• Typ values are used to compute AFE input impedance Z
IN
Table 58-37. Input Capacitance (C
IN
) Values
Gain Selection Single-ended Differential Unit
1 2 2 pF
2 4 4
4 8 8
Table 58-38. Z
IN
Input Impedance
f
S
(MHz) 1 0.5 0.25 0.125 0.0625 0.03125 0.015625 0.007813
C
IN
= 2 pF
Z
IN
(MΩ) 0.5 1 2 4 8 16 32 64
C
IN
= 4 pF
Z
IN
(MΩ) 0.25 0.5 1 2 4 8 16 32
C
IN
= 8 pF
Z
IN
(MΩ) 0.125 0.25 0.5 1 2 4 8 16
58.8.6.1 Track and Hold Time versus Source Output Impedance
The figure below shows a simplified acquisition path.
Figure 58-16. Simplified Acquisition Path
Sample & Hold
Mux.
Z
SOURCE
R
ON
C
IN
ADC
Input
12-bit
AFE Core
During the tracking phase, the AFE tracks the input signal during the tracking time shown below:
t
TRACK
= n × C
IN
× (R
ON
+Z
SOURCE
)/1000
•
Tracking time expressed in ns and Z
SOURCE
expressed in Ω.
• n depends on the expected accuracy
• R
ON
= 2 kOhm
Table 58-39. Number of Tau:n
Resolution (bits) 12 13 14 15 16
RES 0 2 3 4 5
n 8 9 10 11 12
The AFEC already includes a tracking time of 15 t
AFE Clock.
SAM E70/S70/V70/V71 Family
Electrical Characteristics for SAM ...
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echnology Inc.
Datasheet
DS60001527D-page 1840