MAX1338 Datasheet, PDF (21/24 Pages) Maxim Integrated Products – 14-Bit, 4-Channel, Software-Programmable, Multiranging, Simultaneous-Sampling ADC

14-Bit, 4-Channel, Software-Programmable,
Multiranging, Simultaneous-Sampling ADC
SNR = (6.02 x N + 1.76)dB
where N = 14 bits. In reality, there are other noise
sources such as thermal noise, reference noise, and
clock jitter. 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 five harmonics, and the
DC offset.
Signal-to-Noise Plus Distortion (SINAD)
SINAD indicates the converter’s noise and distortion
performance.
SINAD is computed by taking the ratio of the RMS sig-
nal to the RMS noise plus distortion. RMS noise plus
distortion includes all spectral components to the
Nyquist frequency excluding the fundamental and the
DC offset.

SINAD(dB) = 20 × log 
SIGNAL_RMS


^{(NOISE + DISTORTION)}RMS 
Effective Number of Bits (ENOB)
ENOB specifies the global accuracy of an ADC at a spe-
cific 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
Total Harmonic Distortion (THD)
THD is a dynamic indication of how much harmonic
distortion the converter adds to the signal.
THD is the ratio of the RMS sum of the first five harmon-
ics of the fundamental signal to the fundamental itself.
This is expressed as:
THD = 20 ×


log _

2
2
2
2
2^
V₂
+ V₃
+ V₄
+ V₅
+ V₆


V₁

where V₁ is the fundamental amplitude and V₂–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 funda-
mental (maximum signal component) to the RMS value
of the next largest spurious component, excluding DC
offset. SFDR is specified in decibels relative to the car-
rier (dBc).
Aperture Delay
Aperture delay (t_AD) is the time delay from the sampling
clock edge to the instant when an actual sample is taken.
Aperture Jitter
Aperture jitter (t_AJ) is the sample-to-sample variation in
aperture delay.
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 the MAX1338 is measured by
applying a DC -0.5dBFS sine wave to the ON channel
while a high frequency 10kHz -0.5dBFS sine wave is
applied to all OFF channels. An FFT is taken for the ON
channel. From the FFT data, channel-to-channel
crosstalk is expressed in dB as the power ratio of the
DC signal applied to the ON channel and the high-fre-
quency crosstalk signal from the OFF channels.
Power-Supply Rejection (PSRR)
PSRR is defined as the shift in gain error when the ana-
log power supply is changed from 4.75V to 5.25V.
Small-Signal Bandwidth
A -20dBFS sine wave is applied to the MAX1338 input.
The frequency is increased until the amplitude of the
digitized conversion result decreases 3dB.
Full-Power Bandwidth
A -0.5dBFS sine wave is applied to the MAX1338 input.
The frequency is increased until the amplitude of the
digitized conversion result decreases 3dB.
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