Datasheet

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USING THE REF02 AS A POWER SUPPLY BIPOLAR OPERATION USING THE DAC8554
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
DAC8554
AV ,V
DD REF
V X
OUT
AV ,V
DD REF
(Otherpinsomittedforclarity.)
+5V
+6V
±5V
-6V
OPA703
DAC8554
10 Fm 0.1 Fm
R
1
10kW
R
2
10kW
DAC8554
SLAS431B – JUNE 2005 – REVISED OCTOBER 2006
FOR THE DAC8554
The DAC8554 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 DAC8554, a possible configuration is to use a using the circuit in Figure 55 . The circuit shown will
REF02 (+5V precision voltage reference) to supply give an output voltage range of ± V
REF
. Rail-to-rail
the required voltage to the DAC8554 supply input as operation at the amplifier output is achievable using
well as the reference input, as illustrated in an amplifier such as the OPA703 , as shown in
Figure 54 . This is especially useful if the power Figure 55 .
supply is quite noisy or if the system supply voltages
The output voltage for any input code can be
are at some value other than 5V. The REF02 will
calculated as follows:
output a steady supply voltage for the DAC8554. If
the REF02 is used, the current it needs to supply to
the DAC8554 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
where D represents the input code in decimal
current required (with a 5k Ω load on a given DAC
(0–65535).
output) is:
With V
REF
= 5V, R
1
= R
2
= 10k Ω .
0.85mA + (5V/5k Ω ) = 1.085mA
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
DAC8554
Figure 55. Bipolar Operation With the DAC8554
24
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