Datasheet

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USING THE REF02 AS A POWER SUPPLY BIPOLAR OPERATION USING THE DAC8555
V
OUT
X + ƪV
REF
ǒ
D
65536
Ǔ
ǒ
R
1
) R
2
R
1
Ǔ
* V
REF
ǒ
R
2
R
1
Ǔ
ƫ
V
OUT
X +
ǒ
10 D
65536
Ǔ
*5V
REF02
Three-Wire
Serial
Interface
+5V
AI +I
DD REF
V =0Vto5V
OUT
SYNC
SCLK
D
IN
+15V
DAC8555
AV ,V
DD REF
V X
OUT
AV ,V
DD REF
(Otherpinsomittedforclarity.)
+5V
+6V
±5V
-6V
OPA703
DAC8555
10 Fm 0.1 Fm
R
1
10kW
R
2
10kW
DAC8555
SLAS475B – NOVEMBER 2005 – REVISED OCTOBER 2006
FOR THE DAC8555
The DAC8555 has been designed for single-supply
Due to the extremely low supply current required by operation, but a bipolar output range is also possible
the DAC8555, a possible configuration is to use a using the circuit in Figure 55 . The circuit shown will
REF02 +5V precision voltage reference to supply the give an output voltage range of ± V
REF
. Rail-to-rail
required voltage to the DAC8555 supply input as well operation at the amplifier output is achievable using
as the reference input, as shown in Figure 54 . This is an amplifier such as the OPA703 , as shown in
especially useful if the power supply is quite noisy or Figure 55 .
if the system supply voltages are at some value
The output voltage for any input code can be
other than 5V. The REF02 will output a steady
calculated as follows:
supply voltage for the DAC8555. If the REF02 is
used, the current it needs to supply to the DAC8555
is 0.85mA typical for AV
DD
= 5V. When a DAC output
is loaded, the REF02 also needs to supply the
current to the load. The total typical current required
where D represents the input code in decimal
(with a 5k Ω load on a given DAC output) is:
(0–65535).
With V
REF
= 5V, R
1
= R
2
= 10k Ω .
0.85mA + (5V/5k Ω ) = 1.85mA
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.
Figure 54. REF02 as a Power Supply to the
DAC8555
Figure 55. Bipolar Operation With the DAC8555
24
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