Datasheet

AD5304/AD5314/AD5324 Data Sheet
Rev. H | Page 18 of 24
APPLICATIONS INFORMATION
TYPICAL APPLICATION CIRCUIT
The AD5304/AD5314/AD5324 can be used with a wide range
of reference voltages where the devices offer full, one-quadrant
multiplying capability over a reference range of 0 V to V
DD
.
More typically, these devices are used with a fixed, precision
reference voltage. Suitable references for 5 V operation are the
AD780 and REF192 (2.5 V references). For 2.5 V operation, a
suitable external reference would be the AD589, a 1.23 V band
gap reference. Figure 40 shows a typical setup for the AD5304/
AD5314/AD5324 when using an external reference.
AD5304/AD5314/
AD5324
V
DD
= 2.5V TO 5.5
V
SCLK
REFIN
DIN
SYNC
V
OUT
A
V
OUT
B
V
OUT
C
V
OUT
D
GNDA0
SERIAL
INTERFACE
V
OUT
V
IN
EXTERNAL
REFERENCE
AD790/REF192
WITH V
DD
= 5V
OR AD589 WITH
V
DD
= 2.5V
1µF
0.1µF 10µF
00929-040
Figure 40. AD5304/AD5314/AD5324 Using External Reference
If an output range of 0 V to V
DD
is required, the simplest solution is
to connect the reference input to V
DD
. As this supply is not very
accurate and can be noisy, the AD5304/AD5314/AD5324 can
be powered from the reference voltage; for example, using a 5 V
reference such as the REF195. The REF195 can output a steady
supply voltage for the AD5304/AD5314/AD5324. The current
required from the REF195 is 600 A supply current and approxi-
mately 112 A into the reference input. This is with no load on
the DAC outputs. When the DAC outputs are loaded, the REF195
also needs to supply the current to the loads. The total current
required (with a 10 k load on each output) is
712 A + 4 (5 V/10 k) = 2.70 mA
The load regulation of the REF195 is typically 2 ppm/mA, resulting
in an error of 5.4 ppm (27 V) for the 2.7 mA current drawn from
it. This corresponds to a 0.0014 LSB error at eight bits and
0.022 LSB error at 12 bits.
Bipolar Operation Using the AD5304/AD5314/AD5324
The AD5304/AD5314/AD5324 have been designed for single
supply operation, but a bipolar output range is also possible
using the circuit in Figure 41. This circuit gives an output voltage
range of ±5 V. Rail-to-rail operation at the amplifier output is
achievable using an AD820 or an OP295 as the output amplifier.
AD5304
REFIN
GND
V
OUT
A
V
OUT
B
V
OUT
C
V
OUT
D
SERIAL
INTERFACE
DIN SCLK SYNC
V
OUT
V
IN
GND
REF195
1µF
0.1µF10µF
+6V TO +16V
V
DD
+5V
–5V
±5V
+5V
AD820/
OP295
R1 = 10kΩ
R2 = 10kΩ
0
0929-041
Figure 41. Bipolar Operation with the AD5304
The output voltage for any input code can be calculated as follows:
)1/2(
)()2/(
RRREFIN
R1
R2R1DREFIN
V
N
OUT











where:
D is the decimal equivalent of the code loaded to the DAC.
N is the DAC resolution.
REFIN is the reference voltage input:
REFIN = 5 V, R1 = R2 = 10 k
V
OUT
= (10 × D/2
N
) − 5 V