5962-0924001VXC Datasheet, PDF (41/46 Pages) Texas Instruments – 12-Bit, 1-GSPS Analog-to-Digital Converter

ADS5400-SP
www.ti.com
SLAS669C – SEPTEMBER 2010 – REVISED AUGUST 2012
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
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 Pulse Duration/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
duration) to the period of the clock signal, expressed as a percentage.
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 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 into dBFS, the spur in the output FFT is measured in dBFS,
and the difference is the CMRR in dB.
Effective Number of Bits (ENOB)
ENOB is a measure in units of bits of a converter's performance as compared to the theoretical limit based on
quantization noise
ENOB = (SINAD – 1.76)/6.02
(3)
Gain Error
Gain error is the deviation of the ADC actual input full-scale range from its ideal value, given as a percentage of
the ideal input full-scale range.
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. The INL at each analog input value is the difference between the actual transfer function and
this best-fit line, measured in units of LSB.
Offset Error
Offset error is the deviation of output code from mid-code when both inputs are tied to common-mode.
Power-Supply Rejection Ratio (PSRR)
PSRR is a measure of the ability to reject frequencies present on the power supply. The injected frequency level
is translated into dBFS, the spur in the output FFT is measured in dBFS, and the difference is the PSRR in dB.
The measurement calibrates out the benefit of the board supply decoupling capacitors.
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 in the first five harmonics.
SNR + 10log₁₀
P_S
P_N
(4)
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.
Copyright © 2010–2012, Texas Instruments Incorporated
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