GAIN AND OFFSET ADJUST
Connections Using Potentiometers
GAIN and OFFSET adjust pins provide for trim using
external potentiometers. 15-turn potentiometers provide suf-
ficient resolution. Range of adjustment of these trims is at
least
±0.3%
of Full Scale Range. Refer to Figure 6.
Using D/A Converters
The GAIN ADJUST and OFFSET ADJUST circuits of
the DAC714 have been arranged so that these points may
be easily driven by external D/A converters. Refer to
Figure 7. 12-bit D/A converters provide an OFFSET
adjust resolution and a GAIN adjust resolution of 30µV
to 50µV per LSB step.
Nominal values of GAIN and OFFSET occur when the D/A
converters outputs are at approximately half scale, +5V.
OUTPUT VOLTAGE RANGE CONNECTIONS
The DAC714 output amplifier is connected internally to
provide a 20V output range. For other ranges and configu-
rations, see Figures 6 and 7.
DIGITAL INTERFACE
SERIAL INTERFACE
The DAC714 has a serial interface with two data buffers
which can be used for either synchronous or asynchronous
updating of multiple D/A converters. A0 is the enable control
for the input shift register. A1 is the enable for the D/A Latch.
CLK is used to strobe data into the latches enabled by A0 and
A1. A CLR function is also provided and when enabled it sets
the shift register and the D/A Latch to 0000
H
(output voltage
is midscale).
Multiple DAC714s can be connected to the same CLK and
data lines in two ways. The output of the serial shift register
is available as SDO so that any number of DAC714s can be
cascaded on the same input bit stream as shown in Figures
8 and 9. This configuration allows all D/A converters to be
updated simultaneously and requires a minimum number of
control signals. These configurations do require 16N CLK
cycles to load any given D/A converter, where N is the
number of D/A converters.
The DAC714 can also be connected in parallel as shown in
Figure 10. This configuration allows any D/A converter in
the system to be updated in a maximum of 16 CLK cycles.
DAC714
SDI
A
0
A
1
CLR
V
REF
R
BPO
10kΩ
R
FB2
V
REF
10kΩ
10kΩ
Bus
Interface
V
OUT
R
1
R
L
Sense
Output
DCOM
ACOM
R
2
R
3
Alternate Ground
Sense Connection
To +V
CC
0.01µF
(1)
0.01µF
Analog
Power
Supply
System Ground
To –V
CC
NOTE: (1) Locate close to DAC714 package.
FIGURE 5. System Ground Considerations for High-Resolution D/A Converters.
DAC714
SBAS032A
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