DAC8248

–14–

REV. B

ground as shown in Figure 9. The output voltage will be be-

tween +5 V and +10 V depending on the digital input code.

The output expression is given by:

D = Decimal Equivalent of the Digital Input Word

VOLTAGE SWITCHING MODE

Figure 10 shows the DAC8248 in another single supply configu-

ration. The R-2R ladder is used in the voltage switching mode

and functions as a voltage divider. The output voltage (at the

Ω) and

are left open. The reference input voltage must be maintained

this ensures that device accuracy is preserved.

The output voltage expression is given by:

where D = Decimal Equivalent of the Digital Input Word

APPLICATIONS TIPS

GENERAL GROUND MANAGEMENT

Grounding techniques should be tailored to each individual sys-

tem. Ground loops should be avoided, and ground current paths

should be as short as possible and have a low impedance.

The DAC8248’s AGND and DGND pins should be tied to-

gether at the device socket to prevent digital transients from ap-

pearing at the analog output. This common point then becomes

the single ground point connection. AGND and DGND is then

brought out separately and tied to their respective power supply

grounds. Ground loops can be created if both grounds are tied

together at more than one location, i.e., tied together at the de-

vice and at the digital and analog power supplies.

PC board ground plane can be used for the single point ground

connection should the connections not be practical at the device

socket. If neither of these connections are practical or allowed,

then the device should be placed as close as possible to the sys-

tems single point ground connection. Back-to-back Schottky di-

odes should then be connected between AGND and DGND.

POWER SUPPLY DECOUPLING

Power supplies used with the DAC8248 should be well filtered

and regulated. Local supply decoupling consisting of a 1

µF to

10

µF tantalum capacitor in parallel with a 0.1 µF ceramic is

highly recommended. The capacitors should be connected be-

Figure 9. Single Supply Operation (Current Switching Mode)