ADC12D1600CIUT Datasheet, PDF (57/73 Pages) Texas Instruments – ADC12D1000/ADC12D1600 12-Bit, 2.0/3.2 GSPS Ultra High-Speed ADC

ADC12D1000, ADC12D1600
www.ti.com
SNAS480M – MAY 2010 – REVISED MARCH 2013
SUPPLY/GROUNDING, LAYOUT AND THERMAL RECOMMENDATIONS
Power Planes
All supply buses for the ADC should be sourced from a common linear voltage regulator. This ensures that all
power buses to the ADC are turned on and off simultaneously. This single source will be split into individual
sections of the power plane, with individual decoupling and connection to the different power supply buses of the
ADC. Due to the low voltage but relatively high supply current requirement, the optimal solution may be to use a
switching regulator to provide an intermediate low voltage, which is then regulated down to the final ADC supply
voltage by a linear regulator. Please refer to the documentation provided for the ADC12D1000/1600RB for
additional details on specific regulators that are recommended for this configuration.
Power for the ADC should be provided through a broad plane which is located on one layer adjacent to the
ground plane(s). Placing the power and ground planes on adjacent layers will provide low impedance decoupling
of the ADC supplies, especially at higher frequencies. The output of a linear regulator should feed into the power
plane through a low impedance multi-via connection. The power plane should be split into individual power
peninsulas near the ADC. Each peninsula should feed a particular power bus on the ADC, with decoupling for
that power bus connecting the peninsula to the ground plane near each power/ground pin pair. Using this
technique can be difficult on many printed circuit CAD tools. To work around this, zero ohm resistors can be used
to connect the power source net to the individual nets for the different ADC power buses. As a final step, the
zero ohm resistors can be removed and the plane and peninsulas can be connected manually after all other error
checking is completed.
Bypass Capacitors
The general recommendation is to have one 100nF capacitor for each power/ground pin pair. The capacitors
should be surface mount multi-layer ceramic chip capacitors similar to Panasonic part number ECJ-0EB1A104K.
Ground Planes
Grounding should be done using continuous full ground planes to minimize the impedance for all ground return
paths, and provide the shortest possible image/return path for all signal traces.
Power System Example
The ADC12D1000/1600RB uses continuous ground planes (except where clear areas are needed to provide
appropriate impedance management for specific signals), see Figure 76. Power is provided on one plane, with
the 1.9V ADC supply being split into multiple zones or peninsulas for the specific power buses of the ADC.
Decoupling capacitors are connected between these power bus peninsulas and the adjacent ground planes
using vias. The capacitors are located as close to the individual power/ground pin pairs of the ADC as possible.
In most cases, this means the capacitors are located on the opposite side of the PCB to the ADC.
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