Datasheet

REF-x

ToOutput

Amplifier

DAC8218

www.ti.com

SBAS460A –MAY 2009–REVISED DECEMBER 2009

THEORY OF OPERATION

GENERAL DESCRIPTION

The DAC8218 contains eight DAC channels and eight output amplifiers in a single package. Each channel

consists of a resistor-string DAC followed by an output buffer amplifier. The resistor-string section is simply a

string of resistors, each with a value of R, from REF-x to AGND, as shown in Figure 97. This type of architecture

provides DAC monotonicity. The 14-bit binary digital code loaded to the DAC latch determines at which node on

the string the voltage is tapped off before being fed into the output amplifier. The output amplifier multiplies the

DAC output voltage by a gain of six or four. Using a gain of 6 and power supplies allowing for at least 0.5V

headroom, the output span is 9V with a 1.5V reference, 18V with a 3V reference, and 30V with a 5V reference.

Figure 97. Resistor String

CHANNEL GROUPS

The eight DAC channels and two Offset DACs are arranged into two groups (A and B) with four channels and

one Offset DAC per group. Group A consists of DAC-0, DAC-1, DAC-2, DAC-3, and Offset DAC-A. Group B

consists of DAC-4, DAC-5, DAC-6, DAC-7, and Offset DAC-B. Group A derives its reference voltage from

REF-A, and Group B derives its reference voltage from REF-B.

Product Folder Link(s): DAC8218