Analog/digital converter (the accuracy figures of an ADC and how they are tested)
Reading and checking the accuracy figures of an analog/digital converter · offset, gain, DNL and INL in LSB, missing codes, ideal SQNR of 6.02N + 1.76 dB, SINAD and effective bits, and why FFT tests need coherent sampling or a window
Two converters with the same bit count can differ in the number of bits that are actually useful. When buying an ADC, or a board or module built around one, the questions are which accuracy figures the maker quotes, at what input and conditions, and how they were measured. Specify the static errors that matter for DC measurement, the dynamic figures that matter for changing signals, and the test method behind each.
Accuracy specifications of analog-to-digital converters, as chips, boards or modules: static errors (offset, gain, DNL, INL, missing codes), dynamic figures (SQNR, SINAD, effective number of bits) and the test methods behind them. ADC chip architectures and selection are covered on the Analog-to-digital converter (ADC) chip page; audio A/D units on the Analog-to-digital converter for audio page; PLC analog input modules on the Analog input module page; data acquisition modules on the Data acquisition module page.
CNFX editorial research · Sources checked October 12, 2026 · 2 sources
Static errors: offset, gain, DNL, INL and missing codes
Texas Instruments' application report SLAA013, Understanding Data Converters, states that static errors "can be completely described by just four terms. These are offset error, gain error, integral nonlinearity and differential nonlinearity", each expressed in LSB or as a percentage of full-scale range; "an error of 1/2 LSB for an 8-bit converter corresponds to 0.2% FSR." [1]
DNL is the difference between an actual step width and the ideal 1 LSB; "If the DNL exceeds 1 LSB, there is a possibility that the converter can become nonmonotonic", and in an ADC "one or more of the possible 2n binary codes are never output" (missing codes). INL is the deviation of the actual transfer function from a straight line. Offset error affects all codes equally and "can usually be compensated for by a trimming process". [1]
Editorial check of TI's example: 1/2 LSB of an 8-bit converter is 0.5 ÷ 256 ≈ 0.195%, which TI rounds to 0.2% FSR. [1]
Static error
Definition in SLAA013
Source
Offset
Difference between nominal and actual offset point; same for all codes
Vishal Saxena's data converter lecture notes (Boise State University) give the ideal signal-to-quantisation-noise ratio for a full-scale sine as "SQNR=6.02 N+1.76 dB", tabulating 49.9 dB at 8 bits, 62.0 at 10, 74.0 at 12 and 86.0 at 14, and note that "In reality, ADC performance is limited by many other factors", including electronic noise and distortion. [2]
Editorial calculation from that formula: inverting it gives an effective number of bits of (SINAD − 1.76) ÷ 6.02, so a measured SINAD of 74 dB corresponds to 12.0 effective bits, the ideal for a 12-bit converter. [2]
For the FFT measurement behind these figures, the notes require coherent sampling, where "m integral cycles of signal (fin) should fit in N cycles of fs", with fs/N as the FFT bin size; without it the spectrum leaks, and windows are used: Hann for simulated data with near-coherent sampling, Blackman-Harris "for experimental data where coherent sampling can’t be enforced". [2]
Ask the supplier for SINAD or ENOB at your input frequency and amplitude, the sample rate, and whether the FFT used coherent sampling or a window; compare figures only under the same conditions.
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ADC accuracy details
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Signal: [DC; AC frequency range; amplitude]
Resolution: [bits; range]
Static: [offset; gain; DNL; INL; no missing codes]
Dynamic: [SINAD; ENOB; at frequency]
Sample rate: [S/s]
Test method: [FFT coherent or windowed; histogram]
Form: [chip; board; module]
1 company lists this product among what they make. Company figures are quoted from each
company's own website; every card states where the relationship came from.
Silergy
Manufacturing site to be confirmed for the order
Lists analog-to-digital converters (ADCs) among its products.
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Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 13 October 2026
Buyer questions
Which static errors fully describe DC accuracy?
TI's SLAA013 names four: offset, gain, integral nonlinearity and differential nonlinearity. [1]
What does DNL above 1 LSB mean?
TI says the converter may become non-monotonic, and an ADC may have missing codes. [1]
What is the best SQNR an N-bit ADC can reach?
6.02 N + 1.76 dB for a full-scale sine, for example 74 dB at 12 bits. [2]
Why does the FFT test need coherent sampling?
Without a whole number of signal cycles in the record, energy leaks across bins; windows are used when coherence cannot be enforced. [2]
Sources and what still needs a direct check
Sources checked 2026-10-12. Texas Instruments publishes application report SLAA013 on data converters; Vishal Saxena's data converter lecture slides are hosted by the University of Delaware.
