Rainbow Electronics MAX1183 - Manual (Page 16)

MAX1183
(1 Ω to 5Ω), a ferrite bead, or a direct short.
Alternatively, all ground pins could share the same
ground plane, if the ground plane is sufficiently isolated
from any noisy, digital systems ground plane (e.g.
downstream output buffer or DSP ground plane). Route
high-speed digital signal traces away from the sensitive
analog traces of either channel. Make sure to isolate
the analog input lines to each respective converter to
minimize channel-to-channel crosstalk. Keep all signal
lines short and free of 90 degree turns.
Static Parameter Definitions
Integral Nonlinearity (INL)
Integral nonlinearity is the deviation of the values on an
actual transfer function from a straight line. This straight
line can be either a best straight-line fit or a line drawn
between the endpoints of the transfer function, once
offset and gain errors have been nullified. The static lin-
earity parameters for the MAX1183 are measured using
the best straight-line fit method.
Differential Nonlinearity (DNL)
Differential nonlinearity is the difference between an
actual step width and the ideal value of 1LSB. A DNL
error specification of less than 1LSB guarantees no
missing codes and a monotonic transfer function.
Dynamic Parameter
Definitions
Aperture Jitter
Figure 9 depicts the aperture jitter (t AJ ), which is the
sample-to-sample variation in the aperture delay.
Aperture Delay
Aperture delay (t AD ) is the time defined between the
falling edge of the sampling clock and the instant when
an actual sample is taken (Figure 9).
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 quanti-
zation error (residual error). The ideal, theoretical mini-
mum analog-to-digital noise is caused by quantization
error only and results directly from the ADCs resolution
(N-Bits):
SNR dB[max] = 6.02 dB ✕ N + 1.76 dB
In reality, there are other noise sources besides quanti-
zation noise: thermal noise, reference noise, clock jitter,
etc. SNR is computed by taking the ratio of the rms sig-
nal to the rms noise, which includes all spectral compo-
Dual 10-Bit, 40Msps, +3V, Low-Power ADC with
Internal Reference and Parallel Outputs
16 ______________________________________________________________________________________
0 °
90 °
÷8
DOWNCONVERTER
MAX2451
INA+
MAX1183
INA-
INB+
INB-
DSP
POST-
PROCESSING
Figure 8. Typical QAM Application, Using the MAX1183
HOLD
ANALOG
INPUT
SAMPLED
DATA (T/H)
T/H
t AD
t AJ
TRACK TRACK
CLK
Figure 9. T/H Aperture Timing