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THEORY OF OPERATION

D/A SECTION

REF (+)

REF (-)

Resistor

String

Output

Amplifier

GND

DAC Register

V

OUT +

V

DD

D

4096

RESISTOR STRING

R

R

R

R

GND

To Output

Amplifier

DAC7571

SLAS374A – FEBRUARY 2003 – REVISED JANUARY 2004

The architecture of the DAC7571 consists of a string DAC followed by an output buffer amplifier. Figure 39

shows a block diagram of the DAC architecture.

Figure 39. R-String DAC Architecture

The input coding to the DAC7571 is unsigned binary, which gives the ideal output voltage as:

where D = decimal equivalent of the binary code that is loaded to the DAC register; it can range from 0 to 4095.

The resistor string section is shown in Figure 40. It is simply a string of resistors, each of value R. The code

loaded into the DAC register determines at which node on the string the voltage is tapped off to be fed into the

output amplifier by closing one of the switches connecting the string to the amplifier. It is ensured monotonic

because it is a string of resistors. The negative tap of the resistor string is tied to GND. The positive tap of the

Figure 40. Resistor String

13