ADS4449 datasheet(49/56 Pages) TI1

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SINAD = 10Log

P + P

SNR = 10Log

ADS4449

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SBAS603A – APRIL 2013 – REVISED JANUARY 2016

12 Device and Documentation Support

12.1 Device Nomenclature

Analog Bandwidth The analog input frequency at which the power of the fundamental is reduced by 3 dB with

respect to the low-frequency value.

Aperture Delay The delay in time between the rising edge of the input sampling clock and the actual time at

which the sampling occurs. This delay is different across channels. The maximum variation is

specified as an aperture delay variation (channel-to-channel).

Aperture Uncertainty (Jitter) The sample-to-sample variation in aperture delay.

Clock Pulse Width and Duty Cycle The duty cycle of a clock signal is the ratio of the time the clock signal

remains at a logic high (clock pulse width) to the period of the clock signal. Duty cycle is typically

expressed as a percentage. A perfect differential sine-wave clock results in a 50% duty cycle.

Maximum Conversion Rate The maximum sampling rate at which specified operation is given. All parametric

testing is performed at this sampling rate, unless otherwise noted.

Minimum Conversion Rate The minimum sampling rate at which the ADC functions.

Differential Nonlinearity (DNL) An ideal ADC exhibits code transitions at analog input values spaced exactly 1

LSB apart. DNL is the deviation of any single step from this ideal value, measured in units of LSBs.

Integral Nonlinearity (INL) INL is the deviation of the ADC transfer function from a best-fit line determined by a

least-squares curve fit of that transfer function, measured in units of LSBs.

Gain Error

Gain error is the deviation of the ADC actual input full-scale range from the ideal value. Gain error

is given as a percentage of the ideal input full-scale range. Gain error has two components: error as

a result of reference inaccuracy and error as a result of the channel. Both errors are specified

independently as EGREF and EGCHAN.

To a first-order approximation, the total gain error of ETOTAL is approximately EGREF +

EGCHAN.

For example, if ETOTAL = ±0.5%, the full-scale input varies from (1 – 0.5 / 100) × fS ideal to (1 +

0.5 / 100) × fS ideal.

Offset Error Offset error is the difference, given in number of LSBs, between the ADC actual average idle

channel output code and the ideal average idle channel output code. This quantity is often mapped

into millivolts.

Temperature Drift The temperature drift coefficient (with respect to gain error and offset error) specifies the

change per degree Celsius of the parameter from TMIN to TMAX. The coefficient is calculated by

dividing the maximum deviation of the parameter across the TMIN to TMAX range by the difference of

TMAX – TMIN.

Signal-to-Noise Ratio (SNR) SNR is the ratio of the power of the fundamental (PS) to the noise floor power

(PN), excluding the power at dc and the first nine harmonics.

(1)

SNR is either given in units of dBc (dB to carrier) when the absolute power of the

fundamental is used as the reference, or dBFS (dB to full-scale) when the power of the

fundamental is extrapolated to the converter full-scale range.

Signal-to-Noise and Distortion (SINAD) SINAD is the ratio of the power of the fundamental (PS) to the power

of all other spectral components, including noise (PN) and distortion (PD) but excluding dc.

(2)

SINAD is either given in units of dBc (dB to carrier) when the absolute power of the

fundamental is used as the reference, or dBFS (dB to full-scale) when the power of the

fundamental is extrapolated to the converter full-scale range.

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