SPRS230M – OCTOBER 2003 – REVISED MARCH 2011
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6.10.7 On-Chip Analog-to-Digital Converter
Table 6-38. ADC Electrical Characteristics (over recommended operating conditions)
(1) (2)
PARAMETER
DC SPECIFICATIONS
Resolution
ADC clock
60-MHz device
100-MHz device
100-MHz device (F2809 only)
ACCURACY
INL (Integral nonlinearity)
DNL (Differential nonlinearity)
Offset error
(4)
(3)
MIN
12
0.001
0.001
0.001
TYP
MAX
UNIT
Bits
7.5
12.5
25
±1.5
±2
±1
MHz
1–12.5 MHz ADC clock (6.25 MSPS)
12.5–25 MHz ADC clock (12.5 MSPS)
–60
±4
(5)
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
+60
+60
+60
±4
±4
Offset error with hardware trimming
Overall gain error with internal reference
Channel-to-channel offset variation
Channel-to-channel gain variation
ANALOG INPUT
Analog input voltage (ADCINx to ADCLO)
(6)
ADCLO
Input capacitance
Input leakage current
INTERNAL VOLTAGE REFERENCE
(5)
–60
–60
Overall gain error with external reference
0
–5
0
10
3
5
±5
1.275
0.525
0.75
50
V
mV
pF
μA
V
V
V
PPM/°C
V
V
V
dB
dB
dB
Bits
dB
V
ADCREFP
- ADCREFP output voltage at the pin
based on internal reference
V
ADCREFM
- ADCREFM output voltage at the pin
based on internal reference
Voltage difference, ADCREFP - ADCREFM
Temperature coefficient
EXTERNAL VOLTAGE REFERENCE
(5)
(7)
V
ADCREFIN
- External reference voltage input on
ADCREFIN pin 0.2% or better accurate
reference recommended
AC SPECIFICATIONS
SINAD (100 kHz) Signal-to-noise ratio +
distortion
SNR (100 kHz) Signal-to-noise ratio
THD (100 kHz) Total harmonic distortion
ENOB (100 kHz) Effective number of bits
SFDR (100 kHz) Spurious free dynamic range
(1)
(2)
(3)
(4)
(5)
ADCREFSEL[15:14] = 11b
ADCREFSEL[15:14] = 10b
ADCREFSEL[15:14] = 01b
1.024
1.500
2.048
67.5
68
–79
10.9
83
(6)
(7)
Tested at 12.5 MHz ADCCLK.
All voltages listed in this table are with respect to V
SSA2
.
TI specifies that the ADC will have no missing codes.
1 LSB has the weighted value of 3.0/4096 = 0.732 mV.
A single internal/external band gap reference 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 listed for the internal reference
is inclusive of the movement of the internal bandgap over temperature. Gain error over temperature for the external reference option will
depend on the temperature profile of the source used.
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.
TI recommends using high precision external reference TI part REF3020/3120 or equivalent for 2.048-V reference.
126
Electrical Specifications
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