Rainbow Electronics ADC10D040 - Manual (Page 14)

Specification Definitions
APERTURE (SAMPLING) DELAY is that time required after
the fall of the clock input for the sampling switch to open. The
Sample/Hold circuit effectively stops capturing the input sig-
nal and goes into the “hold” mode t
AD
after the clock goes
low.
APERTURE JITTER is the variation in aperture delay from
sample to sample. Aperture jitter shows up as input noise.
CLOCK DUTY CYCLE is the ratio of the time that the clock
waveform is high to the total time of one clock period.
CROSSTALK is coupling of energy from one channel into
the other channel.
DIFFERENTIAL NON-LINEARITY (DNL) is the measure of
the maximum deviation from the ideal step size of 1 LSB.
Measured at 40 MSPS with a ramp input.
EFFECTIVE NUMBER OF BITS (ENOB, or EFFECTIVE
BITS) is another method of specifying Signal-to-Noise and
Distortion Ratio, or SINAD. ENOB is defined as (SINAD −
1.76)/6.02 and says that the converter is equivalent to a
perfect ADC of this (ENOB) number of bits.
FULL POWER BANDWIDTH (FPBW) is the frequency at
which the magnitude of the reconstructed output fundamen-
tal drops 3 dB below its 1 MHz value.
GAIN ERROR is the difference between the ideal and actual
differences between the input levels at which the first and
last code transitions occur. That is, how far this difference is
from Full Scale.
INTEGRAL NON LINEARITY (INL) is a measure of the
maximum deviation of each individual code from a line
drawn from negative full scale (
1 ⁄
2
LSB below the first code
transition) through positive full scale ( 1 ⁄
2
LSB above the last
code transition). The deviation of any given code from this
straight line is measured from the center of that code value.
The end point test method is used. Measured at 40 MSPS
with a ramp input.
INTERMODULATION DISTORTION (IMD) is the creation of
spectral components that are not present in the input as a
result of two sinusoidal frequencies being applied to the ADC
input at the same time. It is defined as the ratio of the power
in the second and third order intermodulation products to the
total power in one of the original frequencies. IMD is usually
expressed in dB.
LSB (LEAST SIGNIFICANT BIT) is the bit that has the
smallest value of weight of all bits. This value is
m * V
REF
/2 n
where “m” is the reference scale factor and “n” is the ADC
resolution, which is 10 in the case of the ADC10D040. The
value of “m” is determined by the logic level at the gain pin
and has a value of 1 when the gain pin is at a logic low and
a value of 2 when the gain pin is at a logic high.
MISSING CODES are those output codes that are skipped
and will never appear at the ADC outputs. These codes
cannot be reached with any input value.
MSB (MOST SIGNIFICANT BIT) is the bit that has the
largest value or weight. Its value is one half of full scale.
OFFSET ERROR is a measure of how far the mid-scale
transition point is from the ideal zero voltage input.
OUTPUT DELAY is the time delay after the rising edge of
the input clock before the data update is present at the
output pins.
OVERRANGE RECOVERY TIME is the time required after
the differential input voltages goes from 1.5V to 0V for the
converter to recover and make a conversion with its rated
accuracy.
PIPELINE DELAY (LATENCY) is the number of clock cycles
between initiation of conversion and when that data is pre-
sented to the output driver stage. New data is available at
every clock cycle, but the data output lags the input by the
Pipeline Delay plus the Output Delay.
POWER SUPPLY REJECTION RATIO (PSRR) can be one
of two specifications. PSRR1 (DC PSRR) is the ratio of the
change in full scale gain error that results from a power
supply voltage change from 3.0V to 3.6V. PSRR2 (AC
PSRR) is measured with a 10 MHz, 250 mV
P-P
signal riding
upon the power supply and is the ratio of the signal ampli-
tude on the power supply pins to the amplitude of that
frequency at the output. PSRR is expressed in dB.
SIGNAL TO NOISE RATIO (SNR) is the ratio, expressed in
dB, of the rms value of the fundamental signal at the output
to the rms value of the sum of all other spectral components
below one-half the sampling frequency, not including har-
monics or d.c.
SIGNAL TO NOISE PLUS DISTORTION (S/(N+D) or SI-
NAD) is the ratio, expressed in dB, of the rms value of the
fundamental signal at the output to the rms value of all of the
other spectral components below half the clock frequency,
including harmonics but excluding d.c.
SPURIOUS FREE DYNAMIC RANGE (SFDR) is the differ-
ence, expressed in dB, between the rms values of the fun-
damental signal at the output and the peak spurious signal,
where a spurious signal is any signal present in the output
spectrum that is not present at the input.
TOTAL HARMONIC DISTORTION (THD) is the ratio, ex-
pressed in dB, of the total of the first nine harmonic levels at
the output to the level of the fundamental at the output. THD
is calculated as
where f
1
is the RMS power of the fundamental (output)
frequency and f
2
through f
10
are the RMS power of the first
9 harmonic frequencies in the output spectrum.
ADC10D040
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