DAC7562T Datasheet, PDF (44/60 Pages) Texas Instruments – Internal Reference

DAC7562T, DAC7563T, DAC8162T
DAC8163T, DAC8562T, DAC8563T
SLASE61A – SEPTEMBER 2015 – REVISED OCTOBER 2015
www.ti.com
Typical Applications (continued)
9.2.2 Up to ±15-V Bipolar Output Using the DAC8562T
The DAC8562T 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 99 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 DAC8562T internal gain set to 2, however, an external 2.5-V reference could also be used (with
DAC8562T internal gain set to 2).
R
G´R
5.5 V
18 V
V_REFOUT
R
DAC8562T
G´R
–
+ _OPA140
–18 V
V_OUT
Figure 99. Bipolar Output Range Circuit Using DAC8562T
The transfer function shown in Equation 11 can be used to calculate the output voltage as a function of the DAC
code, reference voltage and resistor ratio:
V_OUT
æ
= G × V_{REFOUT çè} 2 ×
D_IN
65,536
-
ö
1_÷ø
(11)
where:
D_IN = decimal equivalent of the binary code that is loaded to the DAC register, ranging from 0 to 65,535 for
DAC8562T (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:
V_OUT
= 20 ×
D_IN
65,536
-
10
V
(12)
In this example, the range is set to ±10 V by using a resistor ratio of four, V_REFOUT of 2.5 V, and DAC8562T
internal gain of 2. The resistor sizes must be selected keeping in mind the current sink or source capability of the
DAC8562T internal reference. Using larger resistor values, for example, R = 10 kΩ or larger, is recommended.
The operational amplifier is selectable depending on the requirements of the system.
The DAC8562TEVM and DAC7562TEVM 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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