14.0 Specific Definitions
COMMON MODE REJECTION RATIO is a measure of how
well in-phase signals common to both input pins are rejected.
To calculate CMRR, the change in output offset is measured
while the common mode input voltage is changed.
CMRR = 20 LOG(ΔCommon Input / ΔOutput Offset)
EFFECTIVE NUMBER OF BITS (ENOB, or EFFECTIVE
BITS) – says that the converter is equivalent to a perfect ADC
of this (ENOB) number of bits. LMP90100’s ENOB is a DC
ENOB spec, not the dynamic ENOB that is measured using
FFT and SINAD. Its equation is as follows:
GAIN ERROR is the deviation from the ideal slope of the
transfer function.
INTEGRAL NON-LINEARITY (INL) is a measure of the de-
viation of each individual code from a straight line through the
input to output transfer function. The deviation of any given
code from this straight line is measured from the center of that
code value. The end point fit method is used. INL for this
product is specified over a limited range, per the Electrical
Tables.
NEGATIVE FULL-SCALE ERROR is the difference between
the differential input voltage at which the output code transi-
tions to negative full scale and (-VREF + 1LSB).
NEGATIVE GAIN ERROR is the difference between the neg-
ative full-scale error and the offset error divided by (VREF /
Gain).
NOISE FREE RESOLUTION is a method of specifying the
number of bits for a converter with noise.
ODR Output Data Rate.
OFFSET ERROR is the difference between the differential
input voltage at which the output code transitions from code
0000h to 0001h and 1 LSB.
POSITIVE FULL-SCALE ERROR is the difference between
the differential input voltage at which the output code transi-
tions to positive full scale and (VREF – 1LSB).
POSITIVE GAIN ERROR is the difference between the pos-
itive full-scale error and the offset error divided by (VREF /
Gain).
POWER SUPPLY REJECTION RATIO (PSRR) is a measure
of how well a change in the analog supply voltage is rejected.
PSRR is calculated from the ratio of the change in offset error
for a given change in supply voltage, expressed in dB.
PSRR = 20 LOG (ΔVA / ΔOutput Offset)
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