reference point for the internal bandgap reference. Ideally,
GND would be connected directly to an analog ground
plane. This plane would be separate from the ground con-
nection for the digital components until they are connected
at the power entry point of the system (see Figure 4).
APPLICATIONS
POWER AND GROUNDING
The DAC7612 can be used in a wide variety of situations—
from low power, battery operated systems to large-scale
industrial process control systems. In addition, some appli-
cations require better performance than others, or are par-
ticularly sensitive to one or two specific parameters. This
diversity makes it difficult to define definite rules to follow
concerning the power supply, bypassing, and grounding.
The following discussion must be considered in relation to
the desired performance and needs of the particular system.
The power applied to VDD 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 VDD and VOUT
.
A precision analog component requires careful layout, ad-
equate bypassing, and a clean, well-regulated power supply.
As the DAC7612 is a single-supply, +5V component, it will
often be used in conjunction with digital logic,
microcontrollers, microprocessors, and digital signal proces-
sors. The more digital logic present in the design and the
higher the switching speed, the more difficult it will be to
achieve good performance.
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 10µF and 0.1µF capaci-
tors shown in Figure 4 are strongly recommended and
should be installed as close to VDD and ground as possible.
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 essen-
tially lowpass filter the +5V supply, removing the high
frequency noise (see Figure 4).
Because the DAC7612 has a single ground pin, all return
currents, including digital and analog return currents, must
flow through this pin. The GND pin is also the ground
Digital Circuits
+5V
Power
Supply
+5V
+5V
GND
DAC7612
VDD
GND
+
+
100µF
10µF
0.1µF
GND
Optional
Other
Analog
Components
FIGURE 4. Suggested Power and Ground Connections for a DAC7612 Sharing a +5V Supply with a Digital System.
®
12
DAC7612
BB [ BURR-BROWN CORPORATION ]
