DAC8551IADGKRG4 Datasheet, PDF (19/26 Pages) Texas Instruments – 16-BIT, ULTRA-LOW GLITCH, VOLTAGE OUTPUT

DAC8551
www.ti.com
SLAS429B – APRIL 2005 – REVISED OCTOBER 2006
APPLICATION INFORMATION
USING THE REF02 AS A POWER SUPPLY
FOR THE DAC8551
Due to the extremely low supply current required by
the DAC8551, an alternative option is to use the
REF02 (+5 V precision voltage reference) to supply
the required voltage to the device, as illustrated in
Figure 53.
+15V
+5V
REF02
285mA
Three-Wire
Serial
Interface
SYNC
SCLK
D_IN
DAC8551
V_OUT = 0V to 5V
Figure 53. REF02 as a Power Supply to the
DAC8551
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 DAC8551. If the
REF02 is used, the current it needs to supply to the
DAC8551 is 200µA. 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:
200mA
)
5V
5kW
+
1.2mA
(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 a 3.9LSB error.
BIPOLAR OPERATION USING THE DAC8551
The DAC8551 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:
ƪ ǒ Ǔ ǒ Ǔ ǒ Ǔƫ V_O + V_REF
D
65536
R₁ ) R₂
R₁
* V_REF
R₂
R₁
(3)
where D represents the input code in decimal
(0–65535).
With V_REF = 5V, R₁ = R₂ = 10kΩ.
ǒ Ǔ V_O +
10 D
65536
* 5V
(4)
Using this example, an output voltage range of ±5V
with 0000h corresponding to a –5V output and
FFFFh 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
R₁
10kW
10mF
0.1mF
V_REF
DAC8551
V_FB
V_OUT
R₂
10kW
+6V
OPA703
5V
–6V
Three-Wire
Serial Interface
Figure 54. Bipolar Output Range
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