ADS5522IPAP Datasheet, PDF (11/32 Pages) Texas Instruments – 12-Bit, 80 MSPS Analog-To-Digital Converter

ADS5522
www.ti.com
SBAS320C – MAY 2004 – REVISED FEBRUARY 2007
DEFINITION OF SPECIFICATIONS
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
Offset Error
The offset error is the difference, given in number of
LSBs, between the ADC's actual average idle
channel output code and the ideal average idle
channel output code. This quantity is often mapped
into mV.
The delay in time between the falling 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 Pulse Width/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 certified
operation is given. All parametric testing is performed
at this sampling rate unless otherwise noted.
Minimum Conversion Rate
Temperature Drift
The temperature drift coefficient (with respect to gain
error and offset error) specifies the change per
degree Celsius of the parameter from T_MIN to T_MAX. It
is calculated by dividing the maximum deviation of
the parameter across the T_MIN to T_MAX range by the
difference (T_MAX – T_MIN).
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
(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's full-scale range.
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. The DNL is
the deviation of any single step from this ideal value,
measured in units of LSBs.
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 excluding dc.
SINAD
+
10Log₁₀
P_N
P_S
)
P_D
(2)
Integral Nonlinearity (INL)
The INL is the deviation of the ADC's 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
The gain error is the deviation of the ADC's actual
input full-scale range from its ideal value. The gain
error is given as a percentage of the ideal input
full-scale range. Gain error does not account for
variations in the internal reference voltages (see the
Electrical Specifications section for limits on the
variation of V_(REFP) and V_(REFM)).
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's full-scale range.
Effective Number of Bits (ENOB)
The ENOB is a measure of a converter's
performance as compared to the theoretical limit
based on quantization noise.
ENOB
+
SINAD *
6.02
1.76
(3)
Total Harmonic Distortion (THD)
THD is the ratio of the power of the fundamental (P_S)
to the power of the first eight harmonics (P_D).
THD
+
10Log₁₀
P_S
P_D
(4)
THD is typically given in units of dBc (dB to carrier).
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