AD7243
APPLYING THE AD7243
Power Supply Decoupling
Unipolar (0 V to +5 V) Configuration
The 0 V to +5 V output voltage range is achieved by connecting
To achieve optimum performance when using the AD7243, the
VDD and VSS lines should each be decoupled to DGND using
0.1 µF capacitors. In noisy environments it is recommended
that 10 µF capacitors be connected in parallel with the 0.1 µF
capacitors.
R
OFS to VOUT. Once again, the AD7243 can be operated using
either single or dual supplies. The table for output voltage vs.
digital code is as in Table I, with 2REFIN replaced by REFIN.
Note, for this range, 1 LSB = REFIN • (2–12 ) = (REFIN/4096).
Bipolar (؎5 V) Configuration
The internal scaling resistors provided on the AD7243 allow
several output voltage ranges. The part can produce unipolar
output ranges of 0 V to +5 V or 0 V to +10 V and a bipolar out-
put range of 5 V. Connections for the various ranges are out-
lined below.
The bipolar configuration for the AD7243, which gives an out-
put range of –5 V to +5 V, is achieved by connecting ROFS to
REFIN. The AD7243 must be operated from dual supplies to
achieve this output voltage range. Either offset binary or two’s
complement data format may be selected. Figure 10 shows the
connection diagram for bipolar operation. An AD586 provides
the reference voltage for the DAC but this could be provided by
the on-chip reference by connecting REFOUT to REFIN.
Unipolar (0 V to +10 V) Configuration
The first of the configurations provides an output voltage range
of 0 V to +10 V. This is achieved by connecting the output off-
set resistor ROFS (Pin 13) to AGND. Natural Binary data format
is selected by connecting BIN/COMP (Pin 4) to DGND. In this
configuration, the AD7243 can be operated using either single
or dual supplies. Note that the VDD supply must be ≥+14.25 V
for this range in order to maintain sufficient amplifier head-
room. Dual supplies may be used to improve settling time and
give increased current sink capability for the amplifier. Figure 9
shows the connection diagram for unipolar operation of the
AD7243. Table I shows the digital code vs. analog output for
this configuration.
V
DD
V
DD
R
OFS
2R
2R
+V
IN
V
OUT
AD586
V
OUT
REFIN
DAC
–5V TO + 5V
AD7243*
GND
V
BIN/ COMP
V
DD
AGND
DGND
SS
V
DD
V
V
SS
DD
*ADDITIONAL PINS OMITTED FOR CLARITY
AD7243*
REFOUT
REFIN
2R
2R
R
OFS
Figure 10. Bipolar Configuration with External Reference
Bipolar Operation (Two’s Complement Data Format)
The AD7243 is configured for two’s complement data format
by connecting BIN/COMP (Pin 4) high. The analog output vs.
digital code is shown in Table II.
V
OUT
DAC
0V TO + 10V
BIN/
COMP
Table II. Two’s Complement Bipolar Code Table
Input Data Word
V
SS
AGND
DGND
0V OR V
SS
MSB
LSB Analog Output, VOUT
*ADDITIONAL PINS OMITTED FOR CLARITY
XXXX 0111 1111 1111
XXXX 0000 0000 0001
XXXX 0000 0000 0000
XXXX 1111 1111 1111
XXXX 1000 0000 0001
XXXX 1000 0000 0000
+REFIN × (2047/2048)
+REFIN × (1/2048)
0 V
–REFIN × (1/2048)
–REFIN × (2047/2048)
–REFIN × (2048/2048) = –REFIN
Figure 9. Unipolar (0 V to +10 V) Configuration
Table I. Unipolar Code Table (0 V to +10 V Range)
Input Data Word
MSB
LSB Analog Output, VOUT
X = Don’t Care.
Note: 1 LSB = REFIN/2048.
XXXX 1111 1111 1111 +2 REFIN × (4095/4096)
XXXX 1000 0000 0001 +2 REFIN × (2049/4096)
XXXX 1000 0000 0000 +2 REFIN × (2048/4096)= +REFIN
XXXX 0111 1111 1111 +2 REFIN × (2047/4096)
XXXX 0000 0000 0001 +2 REFIN × (1/4096)
XXXX 0000 0000 0000 0 V
Bipolar Operation (Offset Binary Data Format)
The AD7243 is configured for Offset Binary data format by
connecting BIN/COMP (Pin 4) low. The analog output vs. digi-
tal code may be obtained by inverting the MSB in Table II.
X = Don’t Care.
Note: 1 LSB = 2 REFIN/4096.
REV. A
–8–
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