Rainbow Electronics MAX19515 - Manual (Page 33)

MAX19515
Dual-Channel, 10-Bit, 65Msps ADC
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Small-Signal Noise Floor (SSNF)
SSNF is the integrated noise and distortion power in the
Nyquist band for small-signal inputs. The DC offset is
excluded from this noise calculation. For this converter, a
small signal is defined as a single tone with an amplitude
less than -35dBFS. This parameter captures the thermal
and quantization noise characteristics of the converter
and can be used to help calculate the overall noise fig-
ure of a receive channel. Refer to www.maxim-ic.com for
application notes on Thermal + Quantization Noise Floor.
Signal-to-Noise Ratio (SNR)
For a waveform perfectly reconstructed from digital
samples, the theoretical maximum SNR is the ratio of
the full-scale analog input (RMS value) to the RMS
quantization error (residual error). The ideal, theoretical
minimum analog-to-digital noise is caused by quantiza-
tion error only and results directly from the ADC’s reso-
lution (N bits):
SNR [max] = 6.02 x N + 1.76
In reality, there are other noise sources besides quanti-
zation noise (e.g., thermal noise, reference noise, clock
jitter, etc.). SNR is computed by taking the ratio of the
RMS signal to the RMS noise. RMS noise includes all
spectral components to the Nyquist frequency exclud-
ing the fundamental, the first six harmonics (HD2–HD7),
and the DC offset.
Signal-to-Noise and Distortion (SINAD)
SINAD is computed by taking the ratio of the RMS sig-
nal to the RMS noise plus the RMS distortion. RMS
noise includes all spectral components to the Nyquist
frequency excluding the fundamental, the first six har-
monics (HD2–HD7), and the DC offset. RMS distortion
includes the first six harmonics (HD2–HD7).
Single-Tone Spurious-Free Dynamic Range
(SFDR1 and SFDR2)
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. SFDR1 reflects the
spurious performance based on worst 2nd-order or
3rd-order harmonic distortion. SFDR2 is defined by the
worst spurious component excluding 2nd- and 3rd-
order harmonics and DC offset.
Total Harmonic Distortion (THD)
THD is the ratio of the RMS of the first six harmonics of
the input signal to the fundamental itself. This is
expressed as:
where V 1 is the fundamental amplitude and V 2 –V 7 are
the amplitudes of the 2nd-order through 7th-order har-
monics (HD2–HD7).
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 .
Aperture Delay
The input signal is sampled on the rising edge of the
sampling clock. There is a small delay between the ris-
ing edge of the sampling clock and the actual sampling
instant, which is defined as aperture delay (t
AD ).
Aperture Jitter
Aperture jitter (t AJ ) is defined as the sample-to-sample
time variation in the aperture delay.
Overdrive Recovery Time
Overdrive recovery time is the time required for the
ADC to recover from an input transient that exceeds the
full-scale limits. The specified overdrive recovery time is
measured with an input transient that exceeds the full-
scale limits by ±10%.
Process Information
PROCESS: CMOS
THD
V V V V V V
V
log = ×
+ + + + +
⎛
⎝
⎜
⎜
⎞
⎠
⎟
⎟
20
2
2
3
2
4
2
5
2
6
2
7
2
1
SINAD
NOISE DISTORTION
SIGNAL
RMS RMS
RMS log = ×
+
⎛
⎝
⎜
⎜
⎞
⎠
⎟
⎟
20
2 2
SNR
SIGNAL
NOISE
RMS
RMS
log = Ч
⎛
⎝⎜ ⎞
⎠⎟
20