Datasheet

942
Atmel | SMART SAM D21 [DATASHEET]
Atmel-42181C–SAM-D21_Datasheet–07/2014
Table 36-22. Single-Ended Mode
Notes: 1. Maximum numbers are based on characterization and not tested in production, and for 5% to 95% of the input voltage
range.
2. Respect the input common mode voltage through the following equations (where VCM_IN is the Input channel com-
mon mode voltage) for all VIN:
z VCM_IN < 0.7*VDDANA + VREF/4 – 0.75V
z VCM_IN > VREF/4 – 0.3*VDDANA - 0.1V
3. The ADC channels on pins PA08, PA09, PA10, PA11 are powered from the VDDIO power supply. The ADC perfor-
mance of these pins will not be the same as all the other ADC channels on pins powered from the VDDANA power
supply.
36.9.4.1 Performance with the Averaging Digital Feature
Averaging is a feature which increases the sample accuracy. ADC automatically computes an average value of multiple
consecutive conversions. The numbers of samples to be averaged is specified by the Number-of-Samples-to-be-
collected bit group in the Average Control register (AVGCTRL.SAMPLENUM[3:0]) and the averaged output is available
in the Result register (RESULT).
Table 36-23. Averaging feature
36.9.4.2 Performance with the hardware offset and gain correction
Inherent gain and offset errors affect the absolute accuracy of the ADC. The offset error cancellation is handled by the
Offset Correction register (OFFSETCORR) and the gain error cancellation, by the Gain Correction register
Symbol Parameter Conditions Min. Typ. Max. Units
ENOB Effective Number of Bits With gain compensation - 9.5 9.8 Bits
TUE Total Unadjusted Error 1x gain - 10.5 14.0 LSB
INL Integral Non-Linearity 1x gain 1.0 1.6 3.5 LSB
DNL Differential Non-Linearity 1x gain +/-0.5 +/-0.6 +/-0.95 LSB
Gain Error Ext. Ref. 1x -5.0 0.7 +5.0 mV
Gain Accuracy
Ext. Ref. 0.5x +/-0.2 +/-0.34 +/-0.4 %
Ext. Ref. 2x to 16X +/-0.01 +/-0.1 +/-0.2 %
Offset Error Ext. Ref. 1x -5.0 1.5 +5.0 mV
SFDR Spurious Free Dynamic Range
1x Gain
F
CLK_ADC
= 2.1MHz
F
IN
= 40kHz
A
IN
= 95%FSR
63.1 65.0 67.0 dB
SINAD Signal-to-Noise and Distortion 47.5 59.5 61.0 dB
SNR Signal-to-Noise Ratio 48.0 60.0 64.0 dB
THD Total Harmonic Distortion -65.4 -63.0 -62.1 dB
Noise RMS T = 25°C - 1.0 - mV
Average
Number
Conditions SNR (dB) SINAD (dB) SFDR (dB)
ENOB
(bits)
1
In differential mode, 1x gain,
V
DDANA
=3.0V, V
REF
=1.0V, 350kSps
66.0 65.0 72.8 9.75
8 67.6 65.8 75.1 10.62
32 69.7 67.1 75.3 10.85
128 70.4 67.5 75.5 10.91