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REV. 0
AD5330/AD5331/AD5340/AD5341
–16–
SUGGESTED DATABUS FORMATS
In most applications GAIN and BUF are hard-wired. However,
if more flexibility is required, they can be included in a databus.
This enables you to software program GAIN, giving the option
of doubling the resolution in the lower half of the DAC range.
In a bused system, GAIN and BUF may be treated as data inputs
since they are written to the device during a write operation and
take effect when
LDAC
is taken low. This means that the refer-
ence buffers and the output amplifier gain of multiple DAC
devices can be controlled using common GAIN and BUF lines.
In the case of the AD5330 this means that the databus must be
wider than eight bits. The AD5331 and AD5340 databuses must
be at least 10 and 12 bits wide respectively and are best suited
to a 16-bit databus system.
Examples of data formats for putting GAIN and BUF on a 16-
bit databus are shown in Figure 31. Note that any unused bits
above the actual DAC data may be used for BUF and GAIN.
DAC devices can be controlled using common GAIN and
BUF lines.
AD5331
DB7
DB0
DB1
DB2
DB3
DB4
DB5
DB6
DB7
GAIN
X
X
X
X
BUF
X
X
AD5330
AD5340
DB7
X = UNUSED BIT
Figure 31. GAIN and BUF Data on a 16-Bit Bus
The AD5341 is a 12-bit device that uses byte load, so only four
bits of the high byte are actually used as data. Two of the unused
bits can be used for GAIN and BUF data by connecting them
to the GAIN and BUF inputs; e.g., Bits 6 and 7, as shown in
Figures 32 and 33.
DB0
DB1
DB2
DB3
DB4
DB5
DB6
GAIN
X
X
BUF
X
X
DB9 DB8
DB0
DB1
DB2
DB3
DB4
DB5
DB6
GAIN
BUF
X
X
DB9 DB8
DB10
DB11
DATA
INPUTS
BUF
GAIN
LDAC
CLR
CS
WR
HBEN
AD5341
DB
7
DB
6
8-BIT
DATA BUS
Figure 32. AD5341 Data Format for Byte Load with GAIN
and BUF Data on 8-Bit Bus
In this case, the low byte is written first in a write operation
with HBEN = 0. Bits 6 and 7 of DAC data will be written into
GAIN and BUF registers but will have no effect. The high byte
is then written. Only the lower four bits of data are written into the
DAC high byte register, so Bits 6 and 7 can be GAIN and BUF
data.
LDAC
is used to update the DAC, GAIN and BUF values.
DB8
DB9
HIGH BYTE
LOW BYTE
X = UNUSED BIT
DB0
DB1
DB2
DB3
DB4
DB5
DB6
DB7
X
X
DB10
DB11
BUF GAIN
Figure 33. AD5341 with GAIN and BUF Data on 8-Bit Bus
APPLICATIONS INFORMATION
Typical Application Circuits
The AD5330/AD5331/AD5340/AD5341 can be used with a
wide range of reference voltages, especially if the reference inputs
are configured to be unbuffered, in which case the devices 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, precision reference voltage. Figure 34 shows a typical
setup for the devices when using an external reference connected to
the unbuffered reference inputs. If the reference inputs are unbuf-
fered, the reference input range is from 0.25 V to V
DD
, but if the
on-chip reference buffers are used, the reference range is reduced.
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.
AD5330/AD5331/
AD5340/AD5341
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
10 F
Figure 34. AD5330/AD5331/AD5340/AD5341 Using
External Reference
Driving V
DD
From the Reference Voltage
If an output range of zero to V
DD
is required, the simplest solu-
tion 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 35.
AD5330/AD5331/
AD5340/AD5341
V
OUT
V
DD
GND
V
REF
GND
V
SHDN
V
IN
ADM663/ADM666
VSET
SENSE
6V TO 16V
0.1 F
10 F
0.1 F
Figure 35. Using an ADM663/ADM666 as Power and Refer-
ence to AD5330/AD5331/AD5340/AD5341