The power applied to VDD (as well as VSS, if not grounded)
should be well regulated and low noise. Switching power
supplies and DC/DC converters will often have high-fre-
quency glitches or spikes riding on the output voltage. In
addition, digital components can create similar high-fre-
quency spikes as their internal logic switches states. This
noise can easily couple into the DAC output voltage through
various paths between the power connections and analog
output.
LAYOUT
A precision analog component requires careful layout, ad-
equate bypassing, and clean, well-regulated power supplies.
As the DAC7614 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 achieve good
performance from the converter.
As with the GND connection, VDD 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, the 1µF to 10µF and 0.1µF
capacitors shown in Figure 4 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
lowpass filter the +5V supply, removing the high frequency
noise (see Figure 4).
Because the DAC7614 has a single ground pin, all return
currents, including digital and analog return currents, must
flow through the GND pin. Ideally, GND would be con-
nected 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 (see Figure 4).
Digital Circuits
+5V
+5V
Power Supply
Ground
+5V
DAC7614
Ground
VDD
100µF
+
+
1µF to
10µF
0.1µF
GND
Optional
Other
Analog
Components
FIGURE 4. Suggested Power and Ground Connections for a DAC7614 Sharing a +5V Supply with a Digital System.
®
12
DAC7614
BB [ BURR-BROWN CORPORATION ]
