AD1876JN Analog Devices, AD1876JN Datasheet - Page 4

• Manufacturer Part Number: AD1876JN
• Description: 16-Bit 100 kSPS Sampling ADC
• Manufacturer: Analog Devices

AD1876
Definition of Specifications
NYQUIST FREQUENCY
An implication of the Nyquist sampling theorem, the “Nyquist
Frequency” of a converter is that input frequency which is one-
half the sampling frequency of the converter.
TOTAL HARMONIC DISTORTION
Total harmonic distortion (THD) is measured as the ratio of the
rms sum of the first nineteen harmonic components to the rms
value of a 1 kHz full-scale sine wave input signal and is ex-
pressed in percent (%) or decibels (dB). For input signals or
harmonics that are above the Nyquist frequency, the aliased
component is used.
SIGNAL-TO-NOISE PLUS DISTORTION RATIO
Signal-to-noise plus distortion (S/N+D) is defined to be the ra-
tio of the rms value of the measured input signal to the rms sum
of all other spectral components below the Nyquist frequency,
including harmonics but excluding dc.
D-RANGE DISTORTION
D-range distortion is the ratio of the distortion plus noise to the
signal at a signal amplitude of –60 dB. In this case, an A-weight
filter is used. The value specified for D-range performance is the
ratio measured plus 60 dB.
D
SAMPLE
OUT
BUSY
CAL
CLK
BUSY
D
CLK
CLK
OUT
PREVIOUS LSB
t
A
t
CALB
Figure 2. Recommended AD1876 Conversion Timing
t
SC
t
CH
Figure 1. AD1876 Calibration Timing
t
SL
t
C
1
t
CDH
t
CL
t
CB
t
CD
X
t
CH
2
t
t
CT
S
t
C
(=1/fs)
MSB
t
CL
–4–
t
DCL
BANDWIDTH
The full power bandwidth is that input frequency at which the
amplitude of the reconstructed fundamental is reduced by 3 dB
for a full-scale input.
INTERMODULATION DISTORTION (IMD)
With inputs consisting of sine waves at two frequencies, f
f
of order (m+n), at sum and difference frequencies of mf
where m, n = 0, l, 2, 3. . . . Intermodulation terms are those for
which m or n is not equal to zero. For example, the second or-
der terms are (f
(2f
are expressed as the decibel ratio of the rms sum of the mea-
sured input signals to the rms sum of the distortion terms. The
two signals applied to the converter are of equal amplitude, and
the peak value of their sum is –0.05 dB from full scale. The
IMD products are normalized to a 0 dB input signal.
APERTURE DELAY
Aperture delay is the time required after SAMPLE is taken
LOW for the internal sample-hold of the AD1876 to open, thus
holding the value of V
APERTURE JITTER
Aperture jitter is the variation in the aperture delay from sample
to sample.
b
3
, any device with nonlinearities will create distortion products,
a
+ f
b
), (2f
16
a
– f
a
+ f
b
), (f
b
) and (f
a
IN
+ 2f
17
.
b
a
) and (f
t
LSB
– f
CB
b
), and the third order terms are
a
– 2f
t
A
b
). The IMD products
t
CB
a
REV. A
a
and
nf
b
,