Datasheet

ADuC836
–22–
ADuC836
–23–
PRIMARY AND AUXILIARY ADC NOISE PERFORMANCE
Tables X, XI, and XII show the output rms noise in mV and output
peak-to-peak resolution in bits (rounded to the nearest 0.5 LSB)
for some typical output update rates on both the primary and
auxiliary ADCs. The numbers are typical and are generated at a
differential input voltage of 0 V. The output update rate is selected
via the Sinc Filter (SF) SFR. It is important to note that the
peak-to-peak resolution gures represent the resolution for which
there will be no code icker within a six-sigma limit.
The QuickStart Development system PC software comes com-
plete with an ADC noise evaluation tool. This tool can be easily
used with the evaluation board to see these gures from silicon.
Table X. Primary ADC, Typical Output RMS Noise (V)
Typical Output RMS Noise vs. Input Range and Update Rate; Output RMS Noise in V
SF Data Update
Input Range
Word Rate (Hz) 20 mV 40 mV 80 mV 160 mV 320 mV 640 mV 1.28 V 2.56 V
13 105.3 1.50 1.50 1.60 1.75 3.50 4.50 6.70 11.75
69 19.79 0.60 0.65 0.65 0.65 0.65 0.95 1.40 2.30
255 5.35 0.35 0.35 0.37 0.37 0.37 0.51 0.82 1.25
Table XI. Primary ADC, Peak-to-Peak Resolution (Bits)
Peak-to-Peak Resolution vs. Input Range and Update Rate; Peak-to-Peak Resolution in Bits
SF Data Update
Input Range
Word Rate (Hz) 20 mV 40 mV 80 mV 160 mV 320 mV 640 mV 1.28 V 2.56 V
13 105.3 12 13 14 15 15 15.5 16 16
69 19.79 13.5 14 15 16 16 16 16 16
255 5.35 14 15 16 16 16 16 16 16
Typical RMS Resolution vs. Input Range and Update Rate: RMS Resolution in Bits*
SF Data Update
Input Range
Word Rate (Hz) 20 mV 40 mV 80 mV 160 mV 320 mV 640 mV 1.28 V 2.56 V
13 105.3 14.7 15.7 16 16 16 16 16 16
69 19.79 16 16 16 16 16 16 16 16
255 5.35 16 16 16 16 16 16 16 16
*Based on a six-sigma limit, the rms resolution is 2.7 bits greater than the peak-to-peak resolution.
Table XII. Auxiliary ADC
Typical Output RMS Noise vs. Update Rate*
Output RMS Noise in V
SF Data Update Input Range
Word Rate (Hz) 2.5 V
13 105.3 10.75
69 19.79 2.00
255 5.35 1.15
*ADC converting in Bipolar mode
Peak-to-Peak Resolution vs. Update Rate
1
Peak-to-Peak Resolution in Bits
SF Data Update Input Range
Word Rate (Hz) 2.5 V
13 105.3 16
2
69 19.79 16
255 5.35 16
NOTES
1
ADC converting in Bipolar mode
2
In Unipolar mode, peak-to-peak resolution at 105 Hz is 15 bits.
REV. A
REV. A