Datasheet

REV. 0
AD5334/AD5335/AD5336/AD5344
–16–
SUGGESTED DATABUS FORMATS
In many applications the GAIN input of the AD5334 and
AD5336 may be hard-wired. However, if more flexibility is
required, it can be included in a data bus. This enables the user
to software program GAIN, giving the option of doubling the
resolution in the lower half of the DAC range. In a bused system
GAIN may be treated as a data input since it is written to the
device during a write operation and takes effect when LDAC is
taken low. This means that the output amplifier gain of multiple
DAC devices can be controlled using a common GAIN line.
The AD5336 databus must be at least 10 bits wide and is best
suited to a 16-bit databus system.
Examples of data formats for putting GAIN on a 16-bit databus
are shown in Figure 32. Note that any unused bits above the
actual DAC data may be used for GAIN.
DB0
DB1DB2
DB3DB4DB5DB6
DB7
DB8DB9
GAIN
XX
AD5336
X
X
X = UNUSED BIT
X
Figure 32. AD5336 Data Format for Byte Load with GAIN
Data on 8-Bit Bus
APPLICATIONS INFORMATION
Typical Application Circuits
The AD5334/AD5335/AD5336/AD5344 can be used with a
wide range of reference voltages and offer full, one-quadrant
multiplying capability over a reference range of 0.25 V to V
DD
.
More typically, these devices may be used with a fixed, preci-
sion reference voltage. Figure 33 shows a typical setup for the
devices when using an external reference connected to the refer-
ence inputs. Suitable references for 5 V operation are the AD780
and REF192. For 2.5 V operation, a suitable external reference
would be the AD589, a 1.23 V bandgap reference.
AD5334/AD5335/
AD5336/AD5344
V
OUT
*
0.1␮F
V
DD
= 2.5V TO 5.5V
V
DD
GND
AD780/REF192
WITH V
DD
= 5V
OR
AD589 WITH V
DD
= 2.5V
V
REF
*
GND
V
OUT
V
IN
EXT
REF
*ONLY ONE CHANNEL OF V
REF
AND V
OUT
SHOWN
10␮F
Figure 33. AD5334/AD5335/AD5336/AD5344 Using
External Reference
Driving V
DD
from the Reference Voltage
If an output range of zero to V
DD
is required, the simplest
solution is to connect the reference inputs to V
DD
. As this supply
may not be very accurate, and may be noisy, the
devices
may be powered from the reference voltage, for example
using a 5 V reference such as the ADM663 or ADM666,
as shown in Figure 34.
AD5334/AD5335/
AD5336/AD5344
V
OUT
*
V
DD
GND
V
REF
*
GND
V
OUT(2)
V
IN
ADM663/ADM666
VSET SHDN
SENSE
6V TO 16V
*ONLY ONE CHANNEL OF V
REF
AND V
OUT
SHOWN
0.1␮F
10␮F
0.1␮F
Figure 34. Using an ADM663/ADM666 as Power and
Reference to AD5334/AD5335/AD5336/AD5344
Bipolar Operation Using the AD5334/AD5335/AD5336/AD5344
The AD5334/AD5335/AD5336/AD5344 have been designed
for single supply operation, but bipolar operation is achievable
using the circuit shown in Figure 35. The circuit shown has been
configured to achieve an output voltage range of –5 V < V
O
<
+5 V. Rail-to-rail operation at the amplifier output is achievable
using an AD820 or OP295 as the output amplifier.
The output voltage for any input code can be calculated as
follows:
V
O
= [(1 + R4/R3) × (R2/(R1 + R2) × (2 × V
REF
× D/ 2
N
)] – R4 × V
REF
/R3
where:
D is the decimal equivalent of the code loaded to the DAC, N is
DAC resolution and V
REF
is the reference voltage input.
With:
V
REF
= 2.5 V
R1 = R3 = 10 kΩ
R2 = R4 = 20 kΩ and V
DD
= 5 V.
V
OUT
= (10 × D/2
N
) – 5
AD5334/AD5335/
AD5336/AD5344
GND
V
DD
= 5V
EXT
REF
V
OUT
*
AD780/REF192
WITH V
DD
= 5V
OR
AD589 WITH V
DD
= 2.5V
GND
V
IN
V
OUT
V
REF
*
V
DD
R3
10k⍀
R1
10k⍀
R2
20k⍀
R4
20k⍀
ⴞ5V
+5V
–5V
*ONLY ONE CHANNEL OF V
REF
AND V
OUT
SHOWN
0.1␮F
0.1␮F
10␮F
Figure 35. Bipolar Operation using the AD5334/AD5335/
AD5336/AD5344