Datasheet

DAC7513
15
SBAS157A
www.ti.com
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FIGURE 10. Bipolar Operation with the DAC7513.
DAC7513
V
REF
V
OUT
V
FB
R
1
10kΩ
R
2
10kΩ
3-Wire
Serial
Interface
V
REF
10µF 0.1µF
–5V
±5V
+5V
OPA703
APPLICATIONS
USING REF02 AS A POWER SUPPLY FOR THE
DAC7513
Due to the extremely low supply current required by the
DAC7513, an alternative option is to use a REF02 +5V
precision voltage reference to supply the required voltage to
the part, as shown in Figure 9. This is especially useful if the
power supply is quite noisy or if the system supply voltages
are at some value other than 5V. The REF02 will output a
steady supply voltage for the DAC7513; if the REF02 is
used, the current it needs to supply to the DAC7513 is
132µA. This is with no load on the output of the DAC, so
when the DAC output is loaded, the REF02 also needs to
supply the current to the load. The total current required (with
a 5kΩ load on the DAC output) is:
132µA + (5V/5kΩ) = 1.13mA
The load regulation of the REF02 is typically 0.005%/mA,
which results in an error of 285µV for the 1.13mA current
drawn from it; this corresponds to a 0.2LSB error.
BIPOLAR OPERATION USING THE DAC7513
The DAC7513 has been designed for single-supply operation,
but a bipolar output range is also possible using the circuit in
Figure 10 which will give an output voltage range of ±V
REF
.
Rail-to-rail operation at the amplifier output is achievable using
an OPA703 as the output amplifier.
The output voltage for any input code can be calculated as
follows:
VV
DRR
R
V
R
R
O
REF REF
=






+






−














•• •
4096
12
1
2
1
where D represents the input code in decimal (0 to 4095).
With V
REF
= 5V, R
1
= R
2
= 10kΩ:
V
10•D
4096
– 5V
O
=






This is an output voltage range of ±5V with 000
H
correspond-
ing to a –5V output and FFF
H
corresponding to a +5V output.
Similarly, using V
REF
= 2.5V, ±2.5V output voltage raw can be
achieved.
LAYOUT
A precision analog component requires careful layout, ad-
equate bypassing, and clean, well-regulated power supplies.
As the DAC7513 offers single-supply operation, it will often
be used in close proximity with digital logic, microcontrollers,
microprocessors, and digital signal processors. The more
digital logic present in the design and the higher the switching
speed, the more difficult it will be to achieve good perfor-
mance from the converter.
Due to the single ground pin of the DAC7513, all return
currents, including digital and analog return currents, must
flow through the GND pin, which would, ideally, be connected
directly to an analog ground plane. This plane would be
separate from the ground connection for the digital compo-
nents until they were connected at the power-entry point of
the system.
FIGURE 9. REF02 as Power Supply to the DAC7513.
REF02
DAC7513
3-Wire
Serial
Interface
+5V
132µA (I
DD
+ I
REF
)
V
OUT
= 0V to 5V
SYNC
SCLK
D
IN
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