Datasheet

SAM4E [DATASHEET]
Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14
1438
47.7.2 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 47.7.5.3 “ADC Channel Input Impedance”.
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 MΩ.
47.7.3 ADC Timings
Table 47-29. 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+DAC reference resistor
bridge
(5)
2.4 3 10 kΩ
I
ADVREF
ADVREF Current
(ADV
REF
+ DAC Current)
ADVREF = 3V — 1 1.5 mA
Table 47-30. 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
—
—
16
4
32
8
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
S
Settling Time Settling time to change offset and gain 100 — — ns
t
CAL
Calibration time 200 — — ns