Texas Instruments Digital Signal Processor SM320F2812-HT User Manual
Page 132
SGUS062B
–
JUNE 2009
–
REVISED JUNE 2011
6.29.2 ADC Electrical Characteristics Over Recommended Operating Conditions
Table 6-46. DC Specifications
(1) (2)
T
A
=
–
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
μ
A
INTERNAL VOLTAGE REFERENCE
(6)
Accuracy, ADCV
REFP
1.9
2
2.1
V
Accuracy, ADCV
REFM
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, ADCV
REFP
1.9
2
2.1
V
Accuracy, ADCV
REFM
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-k
Ω
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 (
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 V
DDA
+ 0.3 V or below V
SS
–
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.
132
Electrical Specifications
Copyright
©
2009
–
2011, Texas Instruments Incorporated
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