Data Converter Jitter Calculator

This calculator computes the theoretical SNR and ENOB due to data converter jitter, as well as the maximum allowable aperture jitter.

Theoretical SNR and ENOB due to jitter

t_J(jitter time)

Non-negative

Enter frequency

a positive integer

SNR(Calculated value)

ENOB(Calculated value)

bits

Maximum allowable aperture jitter

Resolution

bits

a positive integer

Enter frequency

a positive integer

t_J(maximum aperture jitter)(Calculated value)

Formula

SNR calculation

SNR(dB) = 20 × log₁₀(1 / (2π × f × t_J))

ENOB calculation

ENOB = (SNR - 1.76) / 6.02

Maximum aperture jitter

t_J = 1 / (2π × f × 2^(N+1))

Jitter vs. SNR

What is the relationship between data converter jitter, phase noise, and SNR?

Clock jitter matters because it introduces uncertainty (noise) into data conversion. Time-domain jitter is equivalent to phase noise in the frequency domain. Phase noise spreads part of the clock signal's power from the fundamental to other frequencies.

Sampling is equivalent to multiplication in the time domain, i.e. convolution in the frequency domain, so the sampling clock spectrum convolves with the input signal spectrum. Because jitter is broadband noise on the clock, it appears as broadband noise on the sampled spectrum and degrades the ADC noise floor.

SNR vs. jitter equation:

SNR_CLK(dB) = -10log σ²_θ

SNR_sig(dB) = 1 / (4π²σ²_τf₀)

For converters above baseband:

SNR(dB) = -20log(2πf_analogt_{rms_jitter})

So, if jitter is the only limit on converter performance, sampling a 70 MHz IF signal while maintaining 75 dB SNR requires maximum clock jitter of about 400 fs.