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THEORY OF OPERATION
D/A SECTION
REF (+)
REF (-)
Resistor
String
Output
Amplifier
V
OUT
GND
V
DD
DAC Register
V
OUT
+ V
DD
D
4096
RESISTOR STRING
R
R
R
R
V
DD
GND
To Output
Amplifier
DAC7571
SLAS374C – FEBRUARY 2003 – REVISED MAY 2006
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
resistor string is tied to V
DD
.
Figure 40. Resistor String
12
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