MAX1266 Datasheet, PDF (16/19 Pages) Maxim Integrated Products – 420ksps, +5V, 6-/2-Channel, 12-Bit ADCs with +2.5V Reference and Parallel Interface

420ksps, +5V, 6-/2-Channel, 12-Bit ADCs
with +2.5V Reference and Parallel Interface
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CLK
;^WR
RD
CONTROL
D11–
D7–D0 _WORD
D0
STATE
ACQUISITION
SAMPLING INSTANT
Figure 10. Timing Diagram for Fastest Conversion
CONTROL WORD
CONVERSION
;D11–D0
ACQUISITION
tion or conversion can cause additional supply noise,
which can make it difficult to achieve true 12-bit perfor-
mance.
Layout, Grounding, and Bypassing
For best performance, use printed circuit boards. Wire-
wrap configurations are not recommended, since the
layout should ensure proper separation of analog and
digital traces. Do not run analog and digital lines paral-
lel to each other, and do not lay out digital signal paths
underneath the ADC package. Use separate analog
and digital PC board ground sections with only one star
point (Figure 11) connecting the two ground systems
(analog and digital). For lowest noise operation, ensure
the ground return to the star ground’s power supply is
low impedance and as short as possible. Route digital
signals far away from sensitive analog and reference
inputs.
High-frequency noise in the power supply, V_DD, could
impair operation of the ADC’s fast comparator. Bypass
V_DD to the star ground with a network of two parallel
capacitors, 0.1µF and 4.7µF, located as close to the
MAX1266/MAX1268s’ power-supply pin as possible.
Minimize capacitor lead length for best supply-noise
rejection and add an attenuation resistor (5Ω) if the
power supply is extremely noisy.
SUPPLIES
+5V
+5V GND
R* = 5Ω
4.7µF
0.1µF
V_DD
GND
COM
+5V DGND
MAX1266
MAX1268
DIGITAL
CIRCUITRY
*OPTIONAL
Figure 11. Power-Supply and Grounding Connections
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