Datasheet

V
A
R
R
R
R
To Output Amplifier
R
DAC101S101, DAC101S101-Q1
SNAS321F –JUNE 2005–REVISED MARCH 2013 www.ti.com
FUNCTIONAL DESCRIPTION
DAC Section
The DAC101S101 is fabricated on a CMOS process with an architecture that consists of a resistor string and
switches that are followed by an output buffer. The power supply serves as the reference voltage. The input
coding is straight binary with an ideal output voltage of:
V
OUT
= V
A
x (D / 1024)
where
• D is the decimal equivalent of the binary code that is loaded into the DAC register and can take on any value
between 0 and 1023 (2)
Resistor String
The resistor string is shown in Figure 37. This string consists of 1024 equal valued resistors in series with a
switch at each junction of two resistors, plus a switch to ground. The code loaded into the DAC register
determines which switch is closed, connecting the proper node to the amplifier. This configuration ensures that
the DAC is monotonic.
Figure 37. DAC Resistor String
Output Amplifier
The output buffer amplifier is a rail-to-rail type, providing an output voltage range of 0V to V
A
. All amplifiers, even
rail-to-rail types, exhibit a loss of linearity as the output approaches the supply rails (0V and V
A
, in this case). For
this reason, linearity is specified over less than the full output range of the DAC. The output capabilities of the
amplifier are described in the Electrical Characteristics Tables.
Serial Interface
The three-wire interface is compatible with SPI, QSPI and MICROWIRE as well as most DSPs. See the Timing
Diagram for information on a write sequence.
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