Datasheet

IN
OUT
D
V = 20 × 10 V
65,536
-
IN
OUT REFOUT
D
V = G × V 2 × 1
65,536
æ ö
-
ç ÷
è ø
R
G R´
G R´
R
V
OUT
V
REFOUT
DAC8562
OPA140
5.5V 18V
–18V
–
+
DAC8562, DAC8563
DAC8162, DAC8163
DAC7562, DAC7563
SLAS719D –AUGUST 2010–REVISED AUGUST 2012 www.ti.com
UP TO ±15-V BIPOLAR OUTPUT USING THE DAC8562
The DAC8562 is designed to be operate from a single power supply providing a maximum output range of AV
DD
volts. However, the DAC can be placed in the configuration shown in Figure 96 in order to be designed into
bipolar systems. Depending on the ratio of the resistor values, the output of the circuit can range anywhere from
±5 V to ±15 V. The design example below shows that the DAC is configured to have its internal reference
enabled and the DAC8562 internal gain set to two, however, an external 2.5-V reference could also be used
(with DAC8562 internal gain set to two).
Figure 96. Bipolar Output Range Circuit Using DAC8562
The transfer function shown in Equation 5 can be used to calculate the output voltage as a function of the DAC
code, reference voltage and resistor ratio:
(5)
where:
D
IN
= decimal equivalent of the binary code that is loaded to the DAC register, ranging from 0 to 65,535 for
aaa DAC8562 (16 bit).
V
REFOUT
= reference output voltage with the internal reference enabled from the DAC V
REFIN
/V
REFOUT
pin
G = ratio of the resistors
An example configuration to generate a ±10-V output range is shown below in Equation 6 with G = 4 and
V
REFOUT
= 2.5 V:
(6)
In this example, the range is set to ±10 V by using a resistor ratio of four, V
REFOUT
of 2.5 V, and DAC8562
internal gain of two. The resistor sizes must be selected keeping in mind the current sink/source capability of the
DAC8562 internal reference. Using larger resistor values, for example R = 10 kΩ or larger is recommended. The
op amp is selectable depending on the requirements of the system.
The DAC8562EVM and DAC7562EVM boards have the option to evaluate the bipolar output application by
installing the components on the pre-placed footprints. For more information see either the DAC8562EVM or
DAC7562EVM product folder.
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Product Folder Links: DAC8562 DAC8563 DAC8162 DAC8163 DAC7562 DAC7563