DAC7617_14 Datasheet, PDF (13/18 Pages) Texas Instruments – Quad, Serial Input, 12-Bit, Voltage Output DIGITAL-TO-ANALOG CONVERTER

LAYOUT
A precision analog component requires careful layout, ad-
equate bypassing, and clean, well-regulated power supplies.
As the DAC7617 offers single-supply operation, it will often
be 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 switch-
ing speed, the more difficult it will be to keep digital noise
from appearing at the converter output.
Due to the DAC7617’s single ground pin, all return currents,
including digital and analog return currents, must flow
through the GND pin. Ideally, GND would be connected
directly to an analog ground plane. This plane would be
separate from the ground connection for the digital compo-
nents until they were connected at the power entry point of
the system (see Figure 3).
The power applied to V_DD should be well regulated and low
noise. Switching power supplies and DC/DC converters will
often have high-frequency glitches or spikes riding on the
output voltage. In addition, digital components can create
similar high-frequency spikes as their internal logic switches
states. This noise can easily couple into the DAC output
voltage through various paths between the power connec-
tions and analog output.
As with the GND connection, V_DD should be connected to
a +3V 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, the 1µF to 10µF and 0.1µF
capacitors shown in Figure 3 are strongly recommended. In
some situations, additional bypassing may be required, such
as a 100µF electrolytic capacitor or even a π filter made up
of inductors and capacitors—all designed to essentially low-
pass filter the +3V supply, removing the high-frequency
noise (see Figure 3).
+3V
Power Supply
+3V
Ground
Digital Circuits
+3V
Ground
100µF +
Optional
+ _{1µF to}
10µF
0.1µF
DAC7617
V_DD
AGND
Other
Analog
Components
FIGURE 3. Suggested Power and Ground Connections for a DAC7617 Sharing a +3V Supply with a Digital System.
DAC7617
13
SBAS185