SAM4S_14 Datasheet, PDF (1161/1231 Pages) ATMEL Corporation – ARM-based Flash MCU

Table 44-52. Input Capacitance Values
1
2 pF
2
2 pF
4
4F
Note: 1. N/A: Not applicable
4 pF
8 pF
pN/A
Table 44-53. Z_IN Input Impedance
f_S (MHz)
1
0.5
Z_IN (MΩ)
0.5
1
Z_IN (MΩ)
0.25
0.5
Z_IN (MΩ)
0.125
0.25
0.25
0.125
C_IN = 2 pF
2
4
C_IN = 4 pF
1
2
C_IN = 8 pF
0.5
1
0.0625 0.03125 0.015625 0.007813
8
16
32
64
4
8
16
32
2
4
8
16
Track and Hold Time versus Source Output Impedance
Figure 44-17 shows a simplified acquisition path.
Figure 44-17. Simplified Acquisition Path
Z_SOURCE
MUX
R_ON
Sample & Hold
C_IN
12-bit ADC Core
In 12-bit mode, during the tracking phase, the ADC needs to track the input signal during the tracking time shown
below:
t_TRACK = 0.054 x Z_SOURCE + 205
with t_TRACK expressed in ns and Z_SOURCE expressed in Ω.
The ADC already includes a tracking time of 15 t_{CP_ADC}
Two cases must be considered:
1. If the calculated tracking time (t_TRACK) is lower than 15 t_{CP_ADC}, then TRACTIM can be set to 0 .
2. If the calculated tracking time (t_TRACK) is higher than 15 t_{CP_ADC}, then TRACTIM must be set to the correct
value.
SAM4S Series [DATASHEET]
Atmel-11100G-ATARM-SAM4S-Datasheet_27-May-14
1161