12

®

DAC7612

FIGURE 4. Suggested Power and Ground Connections for a DAC7612 Sharing a +5V Supply with a Digital System.

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.

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.

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

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).

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.

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 10

µF 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 100

µF 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).

+

+5V

GND

100

µF

Digital Circuits

+5V

GND

+5V

Power

Supply

Other

Analog

Components

V

DD

GND

DAC7612

+

10

µF

0.1

µF

Optional