SM73201 Datasheet, PDF (7/21 Pages) Texas Instruments – 16-Bit, 50 to 250 kSPS, Differential Input, MicroPower ADC

Specification Definitions
APERTURE DELAY is the time between the first falling edge
of SCLK and the time when the input signal is sampled for
conversion.
COMMON MODE REJECTION RATIO (CMRR) 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 from 2V to
3V.
CMRR = 20 LOG ( Δ Common Input / Δ Output Offset)
CONVERSION TIME is the time required, after the input volt-
age is acquired, for the ADC to convert the input voltage to a
digital word.
DIFFERENTIAL NON-LINEARITY (DNL) is the measure of
the maximum deviation from the ideal step size of 1 LSB.
DUTY CYCLE is the ratio of the time that a repetitive digital
waveform is high to the total time of one period. The specifi-
cation here refers to the SCLK.
EFFECTIVE NUMBER OF BITS (ENOB, or EFFECTIVE
BITS) is another method of specifying Signal-to-Noise and
Distortion 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 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 is the difference between Positive Full-
Scale Error and Negative Full-Scale Error and can be calcu-
lated as:
Gain Error = Positive Full-Scale Error − Negative Full-Scale
Error
INTEGRAL NON-LINEARITY (INL) is a measure of the de-
viation of each individual code from a line drawn from ½ LSB
below the first code transition through ½ 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.
MISSING CODES are those output codes that will never ap-
pear at the ADC outputs. The SM73201 is guaranteed not to
have any missing codes.
NEGATIVE FULL-SCALE ERROR is the difference between
the differential input voltage at which the output code transi-
tions from code 0x8001h to 0x8000h and −V_REF + 1 LSB.
NEGATIVE GAIN ERROR is the difference between the neg-
ative full-scale error and the offset error.
OFFSET ERROR is the difference between the differential
input voltage at which the output code transitions from code
0x0000h to 0x0001h and 1 LSB.
POSITIVE FULL-SCALE ERROR is the difference between
the differential input voltage at which the output code transi-
tions from code 0xFFFEh to 0xFFFFh and V_REF - 1 LSB.
POSITIVE GAIN ERROR is the difference between the pos-
itive full-scale error and the offset error.
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. For the
SM73201, V_A is changed from 4.5V to 5.5V.
PSRR = 20 LOG (ΔOutput Offset / ΔV_A)
SIGNAL TO NOISE RATIO (SNR) is the ratio, expressed in
dB, of the rms value of the input signal to the rms value of the
sum of all other spectral components below one-half the sam-
pling frequency, not including harmonics or d.c.
SIGNAL TO NOISE PLUS DISTORTION (S/N+D or
SINAD) Is the ratio, expressed in dB, of the rms value of the
input signal to the rms value of all of the other spectral com-
ponents below one-half the sampling frequency, including
harmonics but excluding d.c.
SPURIOUS FREE DYNAMIC RANGE (SFDR) is the differ-
ence, expressed in dB, between the desired signal amplitude
to the amplitude of the peak spurious spectral component be-
low one-half the sampling frequency, where a spurious spec-
tral component is any signal present in the output spectrum
that is not present at the input and may or may not be a har-
monic.
TOTAL HARMONIC DISTORTION (THD) is the ratio of the
rms total of the first five harmonic components at the output
to the rms level of the input signal frequency as seen at the
output, expressed in dB. THD is calculated as
where A_f1 is the RMS power of the input frequency at the out-
put and A_f2 through A_f6 are the RMS power in the first 5
harmonic frequencies.
THROUGHPUT TIME is the minimum time required between
the start of two successive conversion.
7
www.ti.com