Datasheet

1132
SAM4S Series [DATASHEET]
11100F–ATARM–29-Jan-14
44.8.2 External Reference Voltage
V
ADVREF
is an external reference voltage applied on the pin ADVREF. The quality of the reference voltage V
ADVREF
is
critical to the performance of the ADC. A DC variation of the reference voltage V
ADVREF
is converted to a gain error by the
ADC. The noise generated by V
ADVREF
is converted by the ADC to count noise.
Notes: 1. See Section “Low Voltage Supply”.
2. Over a bandwidth from 20 Hz to 20 MHz.
3. DIFF is Differential mode.
4. SE is Single-ended mode.
5. When the ADC is in Sleep mode, the ADVREF impedance has a minimum of 10 M
Ω.
44.8.3 ADC Timings
Table 44-37. ADVREF Electrical Characteristics
Symbol Parameter Conditions Min Typ Max Unit
V
ADVREF
ADVREF voltage range
Full operational 2.4 — 3.6
V
(1)
2— 2.4
V
N
Input voltage noise
(2)
Gain = 0.5, DIFF
(3)
mode — — 1100
µVrms
Gain = 1, SE
(4)
and DIFF
(3)
— — 550
Gain = 2, SE
(4)
and DIFF
(3)
— — 274
Gain = 4, SE
(4)
mode — — 137
R
ADVREF
ADVREF Input DC
Impedance
ADC reference resistor bridge
(5)
68 10 kΩ
Table 44-38. ADC Timing Characteristics
Symbol Parameter Conditions Min Typ Max Unit
f
ADC
Clock Frequency 1 20 22 MHz
t
CP_ADC
Clock Period 45 50 1000 ns
f
S
Sampling Frequency 0.05 1 1.1 MHz
t
START-UP
ADC Startup time
Sleep mode to Normal mode
Fast Wake-up mode to Normal mode
20
4
30
8
40
12
µs
t
TRACKTIM
Track Time f
ADC
= max value 160——ns
t
CONV
Conversion Time
Number of ADC clock pulses to
perform a conversion
—20—T
CP_ADC
t
SETTLE
Settling Time Settling time to change offset and gain 100 — — ns
t
CAL
Calibration time 200 — — ns