DEFINITION OF SPECIFICATIONS

Analog Bandwidth

Minimum Conversion Rate

Signal-to-Noise and Distortion (SINAD)

Aperture Delay

Aperture Uncertainty (Jitter)

SINAD + 10Log10

P

S

P

N

) PD

Clock Duty Cycle

Signal-to-Noise Ratio (SNR)

Differential Nonlinearity (DNL)

SNR + 10Log10

P

S

P

N

Effective Number of Bits (ENOB)

Spurious-Free Dynamic Range

ENOB +

SINAD * 1.76

6.02

Two-Tone, Third-Order Intermodulation

Integral Nonlinearity (INL)

Maximum Conversion Rate

ADS5240

www.ti.com ...................................................................................................................................................... SBAS326E – JUNE 2004 – REVISED JANUARY 2009

The analog input frequency at which the spectral

This is the minimum sampling rate where the ADC

power of the fundamental frequency (as determined

still works.

by FFT analysis) is reduced by 3dB.

SINAD is the ratio of the power of the fundamental

The delay in time between the rising edge of the input

(PS) to the power of all the other spectral components

sampling clock and the actual time at which the

including noise (PN) and distortion (PD), but not

sampling occurs.

including dc.

The sample-to-sample variation in aperture delay.

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

Pulse width high is the minimum amount of time that

power of the fundamental is extrapolated to the

the ADCLK pulse should be left in logic ‘1’ state to

full-scale range of the converter.

achieve rated performance. Pulse width low is the

minimum time that the ADCLK pulse should be left in

a low state (logic ‘0’). At a given clock rate, these

SNR is the ratio of the power of the fundamental (PS)

specifications define an acceptable clock duty cycle.

to the noise floor power (PN), excluding the power at

dc and the first eight harmonics.

An ideal ADC exhibits code transitions that are

exactly 1 LSB apart. DNL is the deviation of any

single LSB transition at the digital output from an

SNR is either given in units of dBc (dB to carrier)

ideal 1 LSB step at the analog input. If a device

when the absolute power of the fundamental is used

claims to have no missing codes, it means that all

as the reference, or dBFS (dB to full-scale) when the

possible codes (for a 12-bit converter, 4096 codes)

power of the fundamental is extrapolated to the

are present over the full operating range.

full-scale range of the converter.

The ENOB is a measure of converter performance as

The ratio of the power of the fundamental to the

compared

to

the

theoretical

limit

based

on

highest other spectral component (either spur or

quantization noise.

harmonic). SFDR is typically given in units of dBc (dB

to carrier).

Distortion

INL is the deviation of the transfer function from a

Two-tone

IMD3

is

the

ratio

of

power

of

the

reference line measured in fractions of 1 LSB using a

fundamental (at frequencies f1 and f2) to the power of

best straight line or best fit determined by a least

the

worst

spectral

component

of

third-order

square curve fit. INL is independent from effects of

intermodulation distortion at either frequency 2f1 – f2

offset, gain or quantization errors.

or 2f2 – f1. IMD3 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 encode rate at which parametric testing is

the full-scale range of the converter.

performed. This is the maximum sampling rate where

certified operation is given.

Copyright © 2004–2009, Texas Instruments Incorporated

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