SM320F2812-HT
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SGUS062A–JUNE 2009 –REVISED APRIL 2010
6.29.2 ADC Electrical Characteristics Over Recommended Operating Conditions
Table 6-46. DC Specifications(1) (2)
TA= –55°C to 220°C
PARAMETER UNIT
MIN TYP MAX
Resolution 12 Bits
ADC clock(3) 1 kHz
25 MHz
ACCURACY
INL (Integral nonlinearity)(4) 1–18.75 MHz ADC clock ±1.5 LSB
DNL (Differential nonlinearity)(4) 1–18.75 MHz ADC clock ±1 LSB
Offset error(5) –80 80 LSB
Overall gain error with internal –200 200 LSB
reference(6)
Overall gain error with external If ADCREFP-ADCREFM = 1 V ±0.1% –50 50 LSB
reference(7)
Channel-to-channel offset variation ±8 LSB
Channel-to-channel Gain variation ±8 LSB
ANALOG INPUT
Analog input voltage (ADCINx to 0 3 V
ADCLO)(8)
ADCLO –5 0 5 mV
Input capacitance 10 pF
Input leakage current 3 ±5 mA
INTERNAL VOLTAGE REFERENCE(6)
Accuracy, ADCVREFP 1.9 2 2.1 V
Accuracy, ADCVREFM 0.95 1 1.05 V
Voltage difference, ADCREFP – 1 V
ADCREFM
Temperature coefficient 50 PPM/°C
Reference noise 100 V
EXTERNAL VOLTAGE REFERENCE(7)
Accuracy, ADCVREFP 1.9 2 2.1 V
Accuracy, ADCVREFM 0.95 1 1.05 V
Input voltage difference, ADCREFP – 0.99 1 1.01 V
ADCREFM
(1) Not production tested.
(2) Tested at 12.5-MHz ADCCLK
(3) If SYSCLKOUT ≤25 MHz, ADC clock ≤SYSCLKOUT/2
(4) The INL degrades for frequencies beyond 18.75 MHz –25 MHz. Applications that require these sampling rates should use a 20-kΩ
resistor as bias resistor on the ADCRESEXT pin. This improves overall linearity and typical current drawn by the ADC is a few mA more
than 24.9 kW bias.
(5) 1 LSB has the weighted value of 3.0/4096 = 0.732 mV.
(6) A single internal band gap reference (±5% accuracy) sources both ADCREFP and ADCREFM signals, and hence, these voltages track
together. The ADC converter uses the difference between these two as its reference. The total gain error is the combination of the gain
error shown here and the voltage reference accuracy (ADCREFP – ADCREFM). A software-based calibration procedure is
recommended for better accuracy. See F2812 ADC Calibration Application Note (literature number SPRA989) and Section 5.2,
Documentation Support, for relevant documents.
(7) In this mode, the accuracy of external reference is critical for overall gain. The voltage difference (ADCREFP–ADCREFM) determines
the overall accuracy.
(8) Voltages above VDDA + 0.3 V or below VSS – 0.3 V applied to an analog input pin may temporarily affect the conversion of another pin.
To avoid this, the analog inputs should be kept within these limits.
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