MAX1304_11 Datasheet, PDF (33/37 Pages) Maxim Integrated Products – 8-/4-/2-Channel, 12-Bit, Simultaneous-Sampling ADCs with ±10V, ±5V

8-/4-/2-Channel, 12-Bit, Simultaneous-Sampling ADCs
with ±10V, ±5V, and 0 to +5V Analog Input Ranges
Gain Error
Gain error is a figure of merit that indicates how well the
slope of the actual transfer function matches the slope
of the ideal transfer function. For the MAX1304–
MAX1306/MAX1308–MAX1310/MAX1312–MAX1314, the
gain error is the difference of the measured full-scale
and zero-scale transition points minus the difference of
the ideal full-scale and zero-scale transition points.
For the unipolar devices (MAX1304/MAX1305/
MAX1306), the full-scale transition point is from 0xFFE
to 0xFFF and the zero-scale transition point is from
0x000 to 0x001.
For the bipolar devices (MAX1308/MAX1309/MAX1310/
MAX1312/MAX1313/MAX1314), the full-scale transition
point is from 0x7FE to 0x7FF and the zero-scale transi-
tion point is from 0x800 to 0x801.
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_dB[max] = 6.02_dB × N + 1.76_dB
In reality, there are other noise sources such as thermal
noise, reference noise, and clock jitter.
For these devices, SNR is computed by taking the ratio
of the RMS signal to the RMS noise. RMS noise
includes all spectral components to the Nyquist fre-
quency excluding the fundamental, the first five har-
monics, 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.
SINAD(dB)
=
20
x
log
⎛
⎝⎜ ^(NOISE
SIGNAL_RMS
⎞
+ DISTORTION)_{RMS ⎠⎟}
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 as:
ENOB = ^{SINAD − 1.76}
6.02
Total Harmonic Distortion (THD)
THD is the ratio of the RMS sum of the first five harmon-
ics to the fundamental itself. This is expressed as:
⎛
THD ⁼ 20 x log _{⎝⎜⎜}
V₂₂
+
V₃₂
+
V₄₂
V₁
+
V₅₂
+
V₆₂ ^⎞
⎠⎟⎟
where V₁ is the fundamental amplitude, and V₂ through
V₆ are the amplitudes of the 2nd- through 6th-
order harmonics.
Spurious-Free Dynamic Range (SFDR)
SFDR is the ratio of the RMS amplitude of the fundamen-
tal (maximum signal component) to the RMS value of the
next largest spurious component, excluding DC offset.
SFDR is specified in decibels relative to the carrier (dBc).
Channel-to-Channel Isolation
Channel-to-channel isolation indicates how well each
analog input is isolated from the others. The channel-to-
channel isolation for these devices is measured by
applying DC to channel 1 through channel 7 while an
AC 500kHz, -0.4dBFS sine wave is applied to channel
0. An FFT is taken for channel 0 and channel 1 and the
difference (in dB) of the 500kHz magnitudes is reported
as the channel-to-channel isolation.
Aperature Delay
Aperture delay (t_AD) is the time delay from the CONVST
rising edge to the instant when an actual sample is taken.
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