ADS5272_14 Datasheet, PDF (13/33 Pages) Texas Instruments – 8-Channel, 12-Bit, 65MSPS ADC with Serial LVDS Interface

ADS5272
www.ti.com...................................................................................................................................................... SBAS324C – JUNE 2004 – REVISED JANUARY 2009
DEFINITION OF SPECIFICATIONS
Analog Bandwidth
The analog input frequency at which the spectral
power of the fundamental frequency (as determined
by FFT analysis) is reduced by 3dB.
Aperture Delay
The delay in time between the rising edge of the input
sampling clock and the actual time at which the
sampling occurs.
Aperture Uncertainty (Jitter)
The sample-to-sample variation in aperture delay.
Clock Duty Cycle
Pulse width high is the minimum amount of time that
the ADCLK pulse should be left in logic ‘1’ state to
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
specifications define an acceptable clock duty cycle.
Differential Nonlinearity (DNL)
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
ideal 1 LSB step at the analog input. If a device
claims to have no missing codes, it means that all
possible codes (for a 12-bit converter, 4096 codes)
are present over the full operating range.
Effective Number of Bits (ENOB)
The ENOB is a measure of converter performance as
compared to the theoretical limit based on
quantization noise.
ENOB
+
SINAD *
6.02
1.76
Integral Nonlinearity (INL)
INL is the deviation of the transfer function from a
reference line measured in fractions of 1 LSB using a
best straight line or best fit determined by a least
square curve fit. INL is independent from effects of
offset, gain or quantization errors.
Maximum Conversion Rate
The encode rate at which parametric testing is
performed. This is the maximum sampling rate where
certified operation is given.
Minimum Conversion Rate
This is the minimum sampling rate where the ADC
still works.
Signal-to-Noise and Distortion (SINAD)
SINAD is the ratio of the power of the fundamental
(P_S) to the power of all the other spectral components
including noise (P_N) and distortion (P_D), but not
including dc.
SINAD
+
10Log₁₀
P_N
P_S
)
P_D
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
full-scale range of the converter.
Signal-to-Noise Ratio (SNR)
SNR is the ratio of the power of the fundamental (P_S)
to the noise floor power (P_N), excluding the power at
dc and the first eight harmonics.
SNR
+
10Log₁₀
P_S
P_N
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
full-scale range of the converter.
Spurious-Free Dynamic Range
The ratio of the power of the fundamental to the
highest other spectral component (either spur or
harmonic). SFDR is typically given in units of dBc (dB
to carrier).
Two-Tone, Third-Order Intermodulation
Distortion
Two-tone IMD3 is the ratio of power of the
fundamental (at frequencies f₁ and f₂) to the power of
the worst spectral component of third-order
intermodulation distortion at either frequency 2f₁ – f₂
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 full-scale range of the converter.
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