MAX12553 Datasheet, PDF (26/28 Pages) Maxim Integrated Products – 14-Bit, 65Msps, 3.3V ADC

14-Bit, 65Msps, 3.3V ADC
fundamental, the first six harmonics (HD2–HD7), and
the DC offset.
Signal-to-Noise Plus Distortion (SINAD)
SINAD is computed by taking the ratio of the RMS signal
to the RMS noise plus distortion. RMS noise plus distor-
tion includes all spectral components to the Nyquist fre-
quency excluding the fundamental and the DC offset.
Effective Number of Bits (ENOB)
ENOB specifies the dynamic performance of an ADC at
a specific input frequency and sampling rate. An ideal
ADC’s error consists of quantization noise only. ENOB for
a full-scale sinusoidal input waveform is computed from:
ENOB
=
 SINAD − 1.76

6.02

Single-Tone Spurious-Free Dynamic Range
(SFDR)
SFDR is the ratio expressed in decibels of the RMS
amplitude of the fundamental (maximum signal compo-
nent) to the RMS amplitude of the next-largest spurious
component, excluding DC offset.
Total Harmonic Distortion (THD)
THD is the ratio of the RMS sum of the first six harmon-
ics of the input signal to the fundamental itself. This is
expressed as:
₂
2
2
2
2
2^

THD = 20 × log _
V₂
+ V₃
+ V₄
+ V₅ + V₆ + V₇



V₁

where V₁ is the fundamental amplitude, and V₂ through
V₇ are the amplitudes of the 2nd- through 7th-order
harmonics (HD2–HD7).
Intermodulation Distortion (IMD)
IMD is the ratio of the RMS sum of the intermodulation
products to the RMS sum of the two fundamental input
tones. This is expressed as:

IMD
=
20 ×
log ^


V_IM12 + V_IM22 + .......+ V_IM132 + V_IM142
V₁₂ + V₂₂




The fundamental input tone amplitudes (V₁ and V₂) are
at -7dBFS. Fourteen intermodulation products (V_IM_)
are used in the MAX12553 IMD calculation. The inter-
modulation products are the amplitudes of the output
spectrum at the following frequencies, where f_IN1 and
f_IN2 are the fundamental input tone frequencies:
• Second-order intermodulation products:
f_IN1 + f_IN2, f_IN2 - f_IN1
• Third-order intermodulation products:
2 x f_IN1 - f_IN2, 2 x f_IN2 - f_IN1, 2 x f_IN1 + f_IN2, 2 x f_IN2 + f_IN1
• Fourth-order intermodulation products:
3 x f_IN1 - f_IN2, 3 x f_IN2 - f_IN1, 3 x f_IN1 + f_IN2, 3 x f_IN2 + f_IN1
• Fifth-order intermodulation products:
3 x f_IN1 - 2 x f_IN2, 3 x f_IN2 - 2 x f_IN1, 3 x f_IN1 + 2 x f_IN2,
3 x f_IN2 + 2 x f_IN1
Third-Order Intermodulation (IM3)
IM3 is the total power of the third-order intermodulation
products to the Nyquist frequency relative to the total
input power of the two input tones f_IN1 and f_IN2. The
individual input tone levels are at -7dBFS. The third-
order intermodulation products are 2 x f_IN1 - f_IN2, 2 x
f_IN2 - f_IN1, 2 x f_IN1 + f_IN2, 2 x f_IN2 + f_IN1.
Two-Tone Spurious-Free Dynamic Range
(SFDR_TT)
SFDR_TT represents the ratio, expressed in decibels, of
the RMS amplitude of either input tone to the RMS
amplitude of the next-largest spurious component in the
spectrum, excluding DC offset. This spurious compo-
nent can occur anywhere in the spectrum up to Nyquist
and is usually an intermodulation product or a harmonic.
Aperture Delay
The MAX12553 samples data on the falling edge of its
sampling clock. In actuality, there is a small delay
between the falling edge of the sampling clock and the
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