MAX1396 Maxim Integrated Products, MAX1396 Datasheet - Page 15

• Manufacturer Part Number: MAX1396
• Description: (MAX1393 / MAX1396) 1-Channel True-Differential/ 2-Channel Single-Ended
• Manufacturer: Maxim Integrated Products

1.5V to 3.6V, 312.5ksps, 1-Channel True-Differential/
Figure 13. Power-Supply Grounding Connections
SNR is a dynamic figure of merit that indicates the con-
verter’s noise performance. 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 quantization error only and results
directly from the ADC’s resolution (N bits):
In reality, there are other noise sources such as thermal
noise, reference noise, and clock jitter that also
degrade SNR. 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
excluding the fundamental, the first five harmonics, and
the DC offset.
THD is a dynamic figure of merit that indicates 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
V
V
DD
DD
10
(OPTIONAL)
MAX1393/MAX1396
20
SNR
Total Harmonic Distortion (THD)
log
dB[max]
GND
GROUND
POINT
STAR
______________________________________________________________________________________
Signal-to-Noise Ratio (SNR)
2-Channel Single-Ended, 12-Bit, SAR ADCs
V
2
= 6.02
2
POWER SUPPLY
V
3
dB
2
DATA
x N + 1.76
V
V
4
1
2
DV
V
V
DD
CIRCUITRY
5
DD
dB
DIGITAL
2
DGND
GND
V
6
2
where V
V
harmonics.
SFDR is a dynamic figure of merit that indicates the
lowest usable input signal amplitude. SFDR is the ratio
of the RMS amplitude of the fundamental (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).
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:
The fundamental input tone amplitudes (V
at -6.5dBFS. Fourteen intermodulation products (V
are used in the MAX1393/MAX1396 IMD calculation.
The intermodulation products are the amplitudes of the
output spectrum at the following frequencies, where f
and f
• 2nd-order intermodulation products:
• 3rd-order intermodulation products:
• 4th-order intermodulation products:
• 5th-order intermodulation products:
Channel-to-channel crosstalk indicates how well each
analog input is isolated from the others. The channel-to-
channel crosstalk for the MAX1396 is measured by
applying DC to channel 2 while an AC sine wave is
applied to channel 1. An FFT is taken for channel 1 and
channel 2 and the difference (in dB) is reported as the
channel-to-channel crosstalk.
The MAX1393/MAX1396 sample data on the falling
edge of its third SCLK cycle (Figure 14). In actuality,
there is a small delay between the falling edge of the
sampling clock and the actual sampling instant.
Aperture delay (t
IMD
6
f
2 x f
3 x f
3 x f
f
IN1
IN2
are the amplitudes of the 2nd- through 6th-order
IN2
IN1
IN1
, 3 x f
+ f
IN1
Spurious-Free Dynamic Range (SFDR)
1
20
are the fundamental input tone frequencies:
IN2
is the fundamental amplitude, and V
- f
- f
- 2 x f
IN2
IN2
IN2
, f
log
Intermodulation Distortion (IMD)
IN2
, 2 x f
, 3 x f
+ 2 x f
IN2
Channel-to-Channel Crosstalk
AD
- f
V
IM
IN2
IN2
IN1
, 3 x f
) is the time defined between the
1
2
- f
- f
IN1
IN1
IN1
IN2
V
IM
, 2 x f
, 3 x f
2
- 2 x f
2
V
1
2
IN1
IN1
.....
+ f
+ f
Aperture Delay
IN1
V
2
IN2
IN2
V
2
, 3 x f
IM
, 2 x f
, 3 x f
3
1
2
and V
IN1
2
IN2
IN2
V
through
IMN
+ 2 x
2
+ f
+ f
) are
2
IM
IN1
IN1
IN1
15
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