Datasheet

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USING REF02 AS A POWER SUPPLY FOR
BIPOLAR OPERATION USING THE DAC8552
V
OUT
A, B + ƪV
REF
ǒ
D
65536
Ǔ
ǒ
R
1
) R
2
R
1
Ǔ
* V
REF
ǒ
R
2
R
1
Ǔ
ƫ
REF02
Three-Wire
Serial
Interface
+5V
1.34mA
V =0Vto5V
OUT
SYNC
SCLK
D
IN
+15V
DAC8552
V ,
DD
V
REF
V
OUT
A, B +
ǒ
10 D
65536
Ǔ
* 5V
(3)
DAC8552
V
DD
,V
REF
R
2
10kW
R
1
10kW
V
OUT
A,B
+5V
10 Fm 0.1 Fm
–6V
±5V
+6V
OPA703
NOTE:Additionalpinsomittedforclarity.
Three-Wire
SerialInterface
DAC8552
SLAS430A – JULY 2006 – REVISED OCTOBER 2006
the DAC8552 is 340 µ A typical and 500 µ A max for
DAC8552 V
DD
= 5V. When a DAC output is loaded, the REF02
also needs to supply the current to the load. The
Due to the extremely low supply current required by
typical current required (with a 5k Ω load on a given
the DAC8552, a possible configuration is to use a
DAC output) is:
REF02 +5V precision voltage reference to supply the
340 µ A + (5V/5k Ω ) = 1.34mA
required voltage to the DAC8552 supply input as well
as the reference input, as shown in Figure 50 .
The DAC8552 has been designed for single-supply
operation but a bipolar output range is also possible
using the circuit in Figure 51 . The circuit shown here
gives an output voltage range of ± V
REF
. Rail-to-rail
operation at the amplifier output is achievable using
an amplifier such as the OPA703 , as shown in
Figure 51 .
The output voltage for any input code can be
calculated as follows:
(2)
where D represents the input code in decimal
(0–65535).
Figure 50. REF02 as a Power Supply to the
With V
REF
= 5V, R
1
– R
2
= 10k Ω .
DAC8552
This configuration is especially useful if the power
supply is quite noisy or if the system supply voltages
Using this example, an output voltage range of ± 5V
are at some value other than 5V. The REF02 will
with 0000h corresponding to a –5V output and
output a steady supply voltage for the DAC8552. If
FFFFh corresponding to a 5V output can be
the REF02 is used, the current it needs to supply to
achieved. Similarly, using V
REF
= 2.5V, a ± 2.5V
output voltage range can be achieved.
Figure 51. Bipolar Operation with the DAC8552
19
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