SBAA551 June 2022 ADS8661 , ADS8665 , ADS8671 , ADS8675 , ADS8681 , ADS8685 , ADS8689 , ADS8691 , ADS8695 , ADS8699 , INA823 , INA826 , LM317L , LM337L , MUX509 , TPS2661 , TPS560430
3.1 Accuracy and Noise Performance
The following table shows accuracy and noise results of the hardware at 25°C. A differential DC voltage is applied to a random input. The result is compared against the expected value. The effective number of bits (NEFF) and the noise-free bits (NNFREE) are calculated by a histogram with 65535 samples at a sampling speed of 20 kSPS. The measured value is the mean of the histogram.
Table 3-1 Accuracy and Noise
Performance
| Input | VREF | Measured | Expected | |Δcode| | Sigma | NEFF | NNFREE |
|---|---|---|---|---|---|---|---|
| 0 V | ±12.288 V | 32767 | 32768 | 1 | 0.56 | 16.8 bit | 14.1 bit |
| 0 V | ±2.56 V | 32765 | 32768 | 3 | 0.75 | 16.4 bit | 13.7 bit |
| 5.0 V | ±6.144 V | 59444 | 59434 | 10 | 0.74 | 16.4 bit | 13.7 bit |
| 10 V | ±12.288 V | 59442 | 59434 | 8 | 0.61 | 16.7 bit | 14.0 bit |
| –10 V | ±12.288 V | 6092 | 6101 | 9 | 0.62 | 16.6 bit | 13.9 bit |
| 10.5 mA | 5.12 V | 16124 | 16128 | 4 | 0.73 | 16.4 bit | 13.7 bit |
As an example, the following histogram shows the 0-V differential input with ±12.288-V voltage input range using TI's ADS8681EVM-PDK ecosystem software.
Figure 3-1 Histogram Screen Shot