Datasheet

AD5337/AD5338/AD5339
Rev. C | Page 20 of 28
APPLICATIONS
TYPICAL APPLICATION CIRCUIT
The AD5337/AD5338/AD5339 can be used with a wide
range of reference voltages for 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, the REF192,
and the
ADR391 (2.5 V references). For 2.5 V operation, a
suitable external reference would be the
AD589 or AD1580, a
1.23 V band gap reference.
Figure 36 shows a typical setup for
the AD5337/AD5338/AD5339 when using an external reference.
Note that A0 can be high or low.
GND
SDA
0.1µF
REFIN
A0
10µF
1µF
SCL
V
OUT
A
V
OUT
B
03756-036
V
DD
=2.5
V
TO 5.5
V
AD780/REF192/ADR391
WITH V
DD
=5V OR
AD589/AD1580 WITH
V
DD
=2.5V
AD5337/
AD5338/
AD5339
SERIAL
INTERFACE
EXT
REF
V
IN
V
OUT
Figure 36. AD5337/AD5338/AD5339 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
. Because this
supply can be inaccurate and noisy, the AD5337/AD5338/
AD5339 can be powered from a reference voltage, for example,
using a 5 V reference such as the
REF195, which provides a
steady output supply voltage. With no load on the DACs, the
REF195 is required to supply 600 μA supply current to the DAC
and 112 μA to the reference input. When the DAC outputs are
loaded, the REF195 also needs to supply the current to the loads;
therefore, the total current required with a 10 kΩ load on each
output is
712 μA + 2 × (5 V/10 kΩ) = 1.7 mA
The load regulation of the REF195 is typically 2 ppm/mA,
which results in an error of 3.4 ppm (17 μV) for the 1.7 mA
current drawn from it. This corresponds to a 0.0009 LSB error
at 8 bits and a 0.014 LSB error at 12 bits.
BIPOLAR OPERATION
The AD5337/AD5338/AD5339 are designed for single-supply
operation, but a bipolar output range is also possible using the
circuit in
Figure 37. 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.
+5V
–5V
10µF
6V TO 12V
AD5339
0.1µF
R1 = 10kΩ
±5V
R2 = 10kΩ
A0
GND
AD1585
+5V
GND
1µF
03756-037
AD820/
OP295
2-WIRE
SERIAL
INTERFACE
SDA
SCL
REFIN
V
OUT
B
V
OUT
A
V
DD
V
OUT
V
IN
Figure 37. Bipolar Operation with the AD5339
The output voltage for any input code can be calculated as
follows:
⎥
⎦
⎤
⎢
⎣
⎡
×−
+
×
⎟
⎠
⎞
⎜
⎝
⎛
×=
R1
R2
REFIN
R1
R2R1D
REFINV
N
OUT
2
where:
D is the decimal equivalent of the code loaded to the DAC.
N is the DAC resolution.
REFIN is the reference voltage input.
With REFIN = 5 V, R1 = R2 = 10 kΩ:
V
OUT
= (10 × D/2
N
) − 5
MULTIPLE DEVICES ON ONE BUS
Figure 38 shows two AD5339 devices on the same serial bus.
Each has a different slave address because the state of the A0 pin
is different. This allows each of four DACs to be written to or
read from independently.
PULL-UP
RESISTORS
SCL
SDA
AD5339
A0
AD5339
SCL
SDA
A0
V
DD
MICROCONTROLLER
03756-038
Figure 38. Multiple AD5339 Devices on One Bus