Datasheet

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NOISE PERFORMANCE
ADS1232
ADS1234
SBAS350F – JUNE 2005 – REVISED FEBRUARY 2008
The ADS1232/4 offer outstanding noise performance that can be optimized for a given full-scale range using the
on-chip programmable gain amplifier. Table 1 through Table 4 summarize the typical noise performance with
inputs shorted externally for different gains, data rates, and voltage reference values.
The RMS and Peak-to-Peak noise are referred to the input. The Effective Number of Bits (ENOB) is defined as:
• ENOB = ln (FSR/RMS noise)/ln(2)
The Noise-Free Bits are defined as:
• Noise-Free Bits = ln (FSR/Peak-to-Peak Noise)/ln(2)
Where FSR (Full-Scale Range) = V
REF
/Gain
Table 1. AVDD = 5V, V
REF
= 5V, Data Rate = 10SPS
GAIN RMS NOISE PEAK-TO-PEAK NOISE
(1)
ENOB (RMS) NOISE-FREE BITS
1 420nV 1.79µV 23.5 21.4
2 270nV 900nV 23.1 21.4
64 19nV 125nV 22.0 19.2
128 17nV 110nV 21.1 18.4
(1) Peak-to-peak noise data are based on direct measurement.
Table 2. AVDD = 5V, V
REF
= 5V, Data Rate = 80SPS
GAIN RMS NOISE PEAK-TO-PEAK NOISE
(1)
ENOB (RMS) NOISE-FREE BITS
1 1.36µV 8.3µV 21.8 19.2
2 850nV 5.5µV 21.5 18.8
64 48nV 307nV 20.6 18
128 44nV 247nV 19.7 17.2
(1) Peak-to-peak noise data are based on direct measurement.
Table 3. AVDD = 3V, V
REF
= 3V, Data Rate = 10SPS
GAIN RMS NOISE PEAK-TO-PEAK NOISE
(1)
ENOB (RMS) NOISE-FREE BITS
1 450nV 2.8µV 22.6 20
2 325nV 1.8µV 22.1 19.7
64 20nV 130nV 21.2 18.5
128 18nV 115nV 20.3 17.6
(1) Peak-to-peak noise data are based on direct measurement.
Table 4. AVDD = 3V, V
REF
= 3V, Data Rate = 80SPS
GAIN RMS NOISE PEAK-TO-PEAK NOISE
(1)
ENOB (RMS) NOISE-FREE BITS
1 2.2µV 12µV 20.4 17.9
2 1.2µV 6.8µV 20.2 17.8
64 54nV 340nV 19.7 17.1
128 48nV 254nV 18.9 16.5
(1) Peak-to-peak noise data are based on direct measurement of 1024 samples.
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Product Folder Link(s): ADS1232 ADS1234