Max109 – Rainbow Electronics MAX109 User Manual
Page 27
distortion includes all spectral components to the
Nyquist frequency excluding the fundamental and the
DC offset.
Effective Number of Bits (ENOB)
ENOB indicates the global accuracy of an ADC at a
specific input frequency and sampling rate. An ideal
ADC’s error consists of quantization noise only. ENOB
is calculated from a curve fit referenced to the theoreti-
cal full-scale range.
Total Harmonic Distortion (THD)
THD is the ratio of the RMS sum of the first 15 harmon-
ics of the input signal to the fundamental itself. This is
expressed as:
where V1 is the fundamental amplitude, and V
2
through
V
16
are the amplitudes of the 2nd- through 16th-order
harmonics (HD2 through HD16).
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 value of the next largest spurious
component, excluding DC offset.
Third-Order Intermodulation (IM3)
IM3 is the total power of the third-order intermodulation
product to the Nyquist frequency relative to the total
input power of the two input tones, f
IN
1 and f
IN
2. The
individual input tone levels are at -7dBFS. The third-order
intermodulation products are located at 2 x f
IN1
-f
IN2
, 2 x
f
IN2
-f
IN1
, 2 x f
IN1
+f
IN2
, and 2 x f
IN2
+f
IN1
.
Full-Power Bandwidth
A large -1dBFS analog input signal is applied to an
ADC and the input frequency is swept up to the point
where the amplitude of the digitized conversion result
has decreased by -3dB. This point is defined as full-
power input bandwidth frequency.
THD 20 log
V
V
V
2
2
3
2
1
=
×
+
+
+
⎛
⎝
⎜
⎜
⎞
⎠
⎟
⎟
... V
16
2
MAX109
8-Bit, 2.2Gsps ADC with Track/Hold Amplifier
and 1:4 Demultiplexed LVDS Outputs
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