Datasheet

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APPLICATION INFORMATION
USING THE REF02 AS A POWER SUPPLY
200mA )
5V
5kW
+ 1.2mA
(2)
BIPOLAR OPERATION USING THE DAC8551
V
O
+ 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
285 Am
V =0Vto5V
OUT
SYNC
SCLK
D
IN
+15V
DAC8551
V
O
+
ǒ
10 D
65536
Ǔ
* 5V
(4)
DAC8551
V
REF
R
2
10kW
R
1
10kW
V
FB
V
OUT
V
REF
10 Fm 0.1 Fm
–6V
5V
+6V
OPA703
Three-Wire
SerialInterface
DAC8551
SLAS429B – APRIL 2005 – REVISED OCTOBER 2006
The total typical current required (with a 5k Ω load on
the DAC output) is:
FOR THE DAC8551
Due to the extremely low supply current required by
the DAC8551, an alternative option is to use the
The load regulation of the REF02 is typically
REF02 (+5 V precision voltage reference) to supply
0.005%/mA, resulting in an error of 299 µ V for the
the required voltage to the device, as illustrated in
1.2mA current drawn from it. This value corresponds
Figure 53 .
to a 3.9LSB error.
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:
(3)
where D represents the input code in decimal
Figure 53. REF02 as a Power Supply to the
(0–65535).
DAC8551
With V
REF
= 5V, R
1
= R
2
= 10k Ω .
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
Using this example, an output voltage range of ± 5V
REF02 is used, the current it needs to supply to the
with 0000h corresponding to a –5V output and
DAC8551 is 200 µ A. This configuration is with no
FFFFh corresponding to a 5V output can be
load on the output of the DAC. When a DAC output
achieved. Similarly, using V
REF
= 2.5V, a ± 2.5V
is loaded, the REF02 also needs to supply the
output voltage range can be achieved.
current to the load.
Figure 54. Bipolar Output Range
19
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