MAX1196 Datasheet, PDF (20/23 Pages) Maxim Integrated Products – Dual 8-Bit, 40Msps, 3V, Low-Power ADC with Internal Reference and Multiplexed Parallel Outputs

Dual 8-Bit, 40Msps, 3V, Low-Power ADC with
Internal Reference and Multiplexed Parallel Outputs
DOWNCONVERTER
MAX2451
0°
90°
÷₈
A/B
INA+
INA-
MAX1196
INB+
INB-
DSP
POST-
PROCESSING
CHA AND CHB DATA
ALTERNATINGLY
AVAILABLE ON
8-BIT MULTIPLEXED
OUTPUT BUS.
Figure 10. Typical QAM Application Using the MAX1196
as Nyquist or pulse-shaping filters, which remove
unwanted images from the mixing process, thereby
enhancing the overall signal-to-noise (SNR) perfor-
mance and minimizing intersymbol interference.
Grounding, Bypassing,
and Board Layout
The MAX1196 requires high-speed board layout design
techniques. Locate all bypass capacitors as close to
the device as possible, preferably on the same side as
the ADC, using surface-mount devices for minimum
inductance. Bypass V_DD, REFP, REFN, and COM with
two parallel 0.1µF ceramic capacitors and a 2.2µF
bipolar capacitor to GND. Follow the same rules to
bypass the digital supply (OV_DD) to OGND. Multilayer
boards with separated ground and power planes pro-
duce the highest level of signal integrity. Consider the
use of a split ground plane arranged to match the
physical location of the analog ground (GND) and the
digital output-driver ground (OGND) on the ADC’s
package. The two ground planes should be joined at a
single point such that the noisy digital ground currents
do not interfere with the analog ground plane. The ideal
location of this connection can be determined experi-
mentally at a point along the gap between the two
ground planes, which produces optimum results. Make
this connection with a low-value, surface-mount resistor
(1Ω 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 MAX1196 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 11 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
rising edge of the sampling clock and the instant when
an actual sample is taken (Figure 11).
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