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APPLICATION INFORMATION

TRANSITION NOISE

0

52

173

581

176

18

0

0

18

438

1681

5671

2010

182

0

ADS8513

SLAS486 – JUNE 2007

Apply a DC input to the ADS8513 and initiate 1000 conversions. The digital output of the converter varies in

output codes due to the internal noise of the ADS8513. This is true for all 16-bit SAR converters. The transition

noise specification found in the electrical characteristics section is a statistical figure which represents the one

sigma limit or rms value of these output codes.

Using a histogram to plot the output codes, the distribution should appear bell-shaped with the peak of the bell

curve representing the nominal output code for the input voltage value. The ±1

σ, ±2σ, and ±3σ distributions

represent 68.3%, 95.5%, and 99.7% of all codes. Multiplying TN by 6 yields the ±3

σ distribution or 99.7% of all

codes. Statistically, up to 3 codes could fall outside the 5 code distribution when executing 1000 conversions.

The ADS8513 has a TN of 0.8 LSBs which yields 5 output codes for a ±3

σ distribution. Figure 16 and Figure 17

show 1000 and 10000 conversion histogram results.

Figure 16. Histogram of 1000 Conversions With Input Grounded

Figure 17. Histogram of 10000 Conversions With Input Grounded

Copyright © 2007, Texas Instruments Incorporated

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Product Folder Link(s): ADS8513