DAC8551IADGKRG4 Datasheet, PDF (20/26 Pages) Texas Instruments – 16-BIT, ULTRA-LOW GLITCH, VOLTAGE OUTPUT

DAC8551
SLAS429B – APRIL 2005 – REVISED OCTOBER 2006
LAYOUT
A precision analog component requires careful
layout, adequate bypassing, and clean,
well-regulated power supplies.
The DAC8551 offers single-supply operation, and it
often is used in close proximity with digital logic,
microcontrollers, microprocessors, and digital signal
processors. The more digital logic present in the
design and the higher the switching speed, the more
difficult it is to keep digital noise from appearing at
the output.
Due to the single ground pin of the DAC8551, all
return currents, including digital and analog return
currents for the DAC, must flow through a single
point. Ideally, GND would be connected directly to an
analog ground plane. This plane would be separate
from the ground connection for the digital
components until they were connected at the
power-entry point of the system.
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The power applied to V_DD should be well-regulated
and low-noise. Switching power supplies and dc/dc
converters often have high-frequency glitches or
spikes riding on the output voltage. In addition, digital
components can create similar high-frequency
spikes. This noise can easily couple into the DAC
output voltage through various paths between the
power connections and analog output.
As with the GND connection, V_DD should be
connected to a 5V power-supply plane or trace that
is separate from the connection for digital logic until
they are connected at the power-entry point. In
addition, a 1µF to 10µF capacitor and 0.1µF bypass
capacitor are strongly recommended. In some
situations, additional bypassing may be required,
such as a 100µF electrolytic capacitor or even a Pi
filter made up of inductors and capacitors—all
designed to essentially low-pass filter the 5V supply,
removing the high-frequency noise.
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