ADS5474IPFPR datasheet(31/38 Pages) TI

31 / 38 page

www.ti.com

DEFINITION OF SPECIFICATIONS

SNR + 10log10

(4)

SINAD + 10log10

N ) PD

(5)

THD + 10log10

(6)

ADS5474

SLAS525 – JULY 2007

The injected frequency level is translated into dBFS,

the spur in the output FFT is measured in dBFS, and

Analog Bandwidth

the difference is the PSRR in dB. The measurement

The analog input frequency at which the power of the

calibrates out the benefit of the board supply

fundamental is reduced by 3 dB with respect to the

decoupling capacitors.

low-frequency value.

Signal-to-Noise Ratio (SNR)

Aperture Delay

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

The delay in time between the rising edge of the

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

input sampling clock and the actual time at which the

dc and in the first five harmonics.

sampling occurs.

Aperture Uncertainty (Jitter)

The sample-to-sample variation in aperture delay.

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

Clock Pulse Duration/Duty Cycle

when the absolute power of the fundamental is used

The duty cycle of a clock signal is the ratio of the

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

time the clock signal remains at a logic high (clock

power of the fundamental is extrapolated to the

pulse duration) to the period of the clock signal,

converter full-scale range.

expressed as a percentage.

Signal-to-Noise and Distortion (SINAD)

Differential Nonlinearity (DNL)

SINAD is the ratio of the power of the fundamental

An ideal ADC exhibits code transitions at analog

(PS) to the power of all the other spectral

input values spaced exactly 1 LSB apart. DNL is the

components including noise (PN) and distortion (PD),

deviation of any single step from this ideal value,

but excluding dc.

measured in units of LSB.

Common-Mode Rejection Ratio (CMRR)

CMRR measures the ability to reject signals that are

presented to both analog inputs simultaneously. The

injected common-mode frequency level is translated

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

into dBFS, the spur in the output FFT is measured in

when the absolute power of the fundamental is used

dBFS, and the difference is the CMRR in dB.

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

power of the fundamental is extrapolated to the

Effective Number of Bits (ENOB)

converter full-scale range.

ENOB is a measure in units of bits of converter

performance as compared to the theoretical limit

Temperature Drift

based on quantization noise:

Temperature drift (with respect to gain error and

offset error) specifies the change from the value at

ENOB = (SINAD – 1.76)/6.02

the nominal temperature to the value at TMIN or TMAX.

Gain Error

It is computed as the maximum variation the

Gain error is the deviation of the ADC actual input

parameters

over

the

whole

temperature

range

full-scale range from its ideal value, given as a

divided by TMIN – TMAX.

percentage of the ideal input full-scale range.

Total Harmonic Distortion (THD)

Integral Nonlinearity (INL)

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

INL is the deviation of the ADC transfer function from

to the power of the first five harmonics (PD).

a best-fit line determined by a least-squares curve fit

of that transfer function. The INL at each analog

input value is the difference between the actual

transfer function and this best-fit line, measured in

THD is typically given in units of dBc (dB to carrier).

units of LSB.

Two-Tone Intermodulation Distortion (IMD3)

Offset Error

IMD3 is the ratio of the power of the fundamental (at

Offset error is the deviation of output code from

frequencies f1, f2) to the power of the worst spectral

mid-code

when

both

inputs

are

tied

component at either frequency 2f1 – f2 or 2f2 – f1).

common-mode.

IMD3 is given in units of either dBc (dB to carrier)

Power-Supply Rejection Ratio (PSRR)

when the absolute power of the fundamental is used

PSRR

measure

the

ability

reject

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

frequencies present on the power supply.

power of the fundamental is extrapolated to the

converter full-scale range.

Submit Documentation Feedback

ADS5474IPFPR Datasheet(PDF) 31 Page - Texas Instruments

ADS5474IPFPR Datasheet(HTML) 31 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

Datasheet Download

Link URL