DAC8043FZ View Datasheet(PDF) - Analog Devices
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DAC8043FZ Datasheet PDF : 12 Pages
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Table II. Bipolar (Offset Binary) Code Table
Digital Input
MSB
LSB
Nominal Analog Output
(VOUT as Shown in Figure 7)
1111 1111 1111
2047
+VREF 2048
1000 0000 0001
1000 0000 0000
0111 1111 1111
1
+VREF 2048
0
1
–VREF 2048
0000 0000 0001
2047
–VREF 2048
0000 0000 0000
2048
–VREF 2048
NOTES
1Nominal full scale for the circuit of Figure 7 is given by
2047
FS = VREF 2048 .
2Nominal LSB magnitude for the circuit of Figure 7 is given by
1
LSB = VREF 2048 .
BIPOLAR OPERATION (4-QUADRANT)
Figure 7 details a suggested circuit for bipolar, or offset binary
operation. Table II shows the digital input to analog output re-
lationship. The circuit uses offset binary coding. Two’s comple-
ment code can be converted to offset binary by software
inversion of the MSB or by the addition of an external inverter
to the MSB input.
DAC8043
Resistors R3, R4, and R5 must be selected to match within 0.01%
and must all be of the same (preferably metal foil) type to assure
temperature coefficient matching. Mismatching between R3 and
R4 causes offset and full scale errors while an R5 to R4 and R3
mismatch will result in full-scale error.
Calibration is performed by loading the DAC register with 1000
0000 0000 and adjusting R1 until VOUT = 0 V. R1 and R2 may
be omitted, adjusting the ratio of R3 to R4 to yield VOUT = 0 V.
Full scale can be adjusted by loading the DAC register with
1111 1111 1111 and either adjusting the amplitude of VREF or
the value of R5 until the desired VOUT is achieved.
ANALOG/DIGITAL DIVISION
The transfer function for the DAC8043 connected in the multi-
plying mode as shown in Figures 5, 6 and 7 is:
VO
=
–VIN
A1
21
+
A2
22
+
A3
23
+...
A12
212
where AX assumes a value of 1 for an “ON” bit and 0 for an
“OFF” bit.
The transfer function is modified when the DAC is connected in
the feedback of an operational amplifier as shown in Figure 8
and becomes:
–V IN
VO
=
A1
21
+
A2
22
+
A3
23
+.
..
A12
24
The above transfer function is the division of an analog voltage
(VREF) by a digital word. The amplifier goes to the rails with all
bits “OFF” since division by zero is infinity. With all bits “ON,”
the gain is 1 (± 1 LSB). The gain becomes 4096 with the LSB,
bit 12 “ON.”
Figure 7. Bipolar Operation (4-Quadrant, Offset Binary)
REV. C
–9–
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