ADC08D1520QML-SP Datasheet, PDF (18/59 Pages) Texas Instruments – ADC08D1520QML Low Power, 8-Bit, Dual 1.5 GSPS or Single 3.0 GSPS A/D Converter

ADC08D1520QML-SP
SNAS420O – JANUARY 2008 – REVISED MARCH 2013
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Specification Definitions
APERTURE (SAMPLING) DELAYis the amount of delay, measured from the sampling edge of the Clock input,
after which the signal present at the input pin is sampled inside the device.
APERTURE JITTER (t_AJ) is the variation in aperture delay from sample to sample. Aperture jitter shows up as
input noise.
CODE ERROR RATE (C.E.R.) is the probability of error and is defined as the probable number of word errors on
the ADC output per unit of time divided by the number of words seen in that amount of time.. A C.E.R. of 10^-18
corresponds to a statistical error in one word about every four (4) years.
CLOCK DUTY CYCLE is the ratio of the time that the clock waveform is at a logic high to the total time of one
clock period.
DIFFERENTIAL NON-LINEARITY (DNL) is the measure of the maximum deviation from the ideal step size of 1
LSB. Measured at sample rate = 500 MSPS with a 1MHz input sinewave.
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 a measure of the frequency at which the reconstructed output
fundamental drops 3 dB below its low frequency value for a full-scale input.
GAIN ERROR is the deviation from the ideal slope of the transfer function. It can be calculated from Offset and
Full-Scale Errors:
Positive Gain Error = Offset Error − Positive Full-Scale Error
Negative Gain Error = −(Offset Error − Negative Full-Scale Error)
Gain Error = Negative Full-Scale Error − Positive Full-Scale Error = Positive Gain Error + Negative Gain
Error
INTEGRAL NON-LINEARITY (INL) is a measure of worst case deviation of the ADC transfer function from an
ideal straight line drawn through the ADC transfer function. The deviation of any given code from this straight line
is measured from the center of that code value. The best fit method is used.
INTERMODULATION DISTORTION (IMD) is the creation of additional spectral components 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 power in one of the original frequencies. IMD is
usually expressed in dBFS.
LSB (LEAST SIGNIFICANT BIT) is the bit that has the smallest value or weight of all bits. This value is
V_FS / 2^N
(1)
where V_FS is the differential full-scale amplitude V_IN as set by the FSR input and "N" is the ADC resolution in bits,
which is 8, for the ADC08D1520.
LOW VOLTAGE DIFFERENTIAL SIGNALING (LVDS) DIFFERENTIAL OUTPUT VOLTAGE (V_OD) is the
absolute value of the difference between the V_D+ and V_D- outputs; each measured with respect to Ground.
VD+
VD-
GND
VOS
VOD
VD+
VD-
VOD = | VD+ - VD- |
Figure 2.
LVDS OUTPUT OFFSET VOLTAGE (V_OS) is the midpoint between the D+ and D- pins output voltage with
respect to ground; ie., [(V_D+) +( V_D-)]/2.
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