DAC8550_15 Datasheet, PDF (19/28 Pages) Texas Instruments – 16-BIT, ULTRA-LOW GLITCH, VOLTAGE OUTPUT DIGITAL-TO-ANALOG CONVERTER

DAC8550
www.ti.com
SLAS476E – MARCH 2006 – REVISED MARCH 2012
APPLICATION INFORMATION
USING THE REF02 AS A POWER SUPPLY
FOR THE DAC8550
Due to the extremely low supply current required by
the DAC8550, an alternative option is to use a REF02
+5V precision voltage reference to supply the
required voltage to the device, as shown in Figure 53.
+15V
+5V
REF02
285mA
Three-Wire
Serial
Interface
SYNC
SCLK
D_IN
DAC8550
V_OUT = 0V to 5V
200
mA
)
5V
5 kW
+
1.2
mA
(2)
The load regulation of the REF02 is typically
0.005%/mA, resulting in an error of 299μV for the
1.2mA current drawn from it. This value corresponds
to an 8.9LSB error.
BIPOLAR OPERATION USING THE DAC8550
The DAC8550 has been designed for single-supply
operation, but a bipolar output range is also possible
using the circuit in Figure 54. The circuit shown gives
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:
ƪǒ Ǔ ǒ Ǔ ǒ Ǔƫ V_O +
V_REF
2
)
V_REF
D
65536
R₁ ) R₂
R₁
* V_REF
R₂
R₁
(3)
where D represents the input code in 2's complement
(–32768 to +32767).
Figure 53. REF02 as a Power Supply to the
DAC8550
This configuration 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 outputs
a steady supply voltage for the DAC8550. If the
REF02 is used, the current it needs to supply to the
DAC8550 is 250μA. This configuration is with no load
on the output of the DAC. When a DAC output is
loaded, the REF02 also needs to supply the current
to the load. The total typical current required (with a
5kΩ load on the DAC output) is:
With V_REF = 5V, R₁ = R₂ = 10kΩ.
V_O + 10
D
65536
(4)
Using this example, an output voltage range of ±5V
with 8000h corresponding to a –5V output and 8FFFh
corresponding to a 5V output can be achieved.
Similarly, using V_REF = 2.5V, a ±2.5V output voltage
range can be achieved.
V
REF
R₂
10kW
R₁
+6V
10kW
OPA703
5V
V_FB
V_{REF DAC8550} V_OUT
10mF
0.1mF
-6V
Three-Wire
Serial Interface
Figure 54. Bipolar Output Range
Copyright © 2006–2012, Texas Instruments Incorporated
Product Folder Link(s): DAC8550
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