DAC8728 datasheet(32/52 Pages) TI

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REF

ToOutput

Amplifier

DAC8728

SBAS466A – JUNE 2009 – REVISED NOVEMBER 2009

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THEORY OF OPERATION

GENERAL DESCRIPTION

The DAC8728 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 to AGND, as shown in Figure 95. This type of architecture

provides DAC monotonicity. The 16-bit binary digital code loaded to the DAC register 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. The output span is 9V with a 1.5V reference, 18V with a 3V

reference, and 30V for a 5V reference when using dual power supplies of ±16.5V and a gain of 6.

Figure 95. 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.

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DAC8728 Datasheet(PDF) 32 Page - Texas Instruments