DAC8562
+5V
20
0.1µF
FULL SCALE
ADJUST
R4
23.7k
10µF
Ω
P2
500
Ω
+5V
R1
10k
V
DD
Ω
DATA
8
4
V
13
2
OUT
A1
1
R2
R3
–5V
≤ V ≤ +5V
O
DAC-8562
12.7k
247k
Ω
3
16
15
CE
CLR
REFOUT 14
–2.5V
R6
10k
–5V
AGND
12
DGND
10
Ω
P1
Ω
10k
R5
10kΩ
ZERO SCALE
ADJUST
6
5
A1, A2 = 1/2 OP-295
7
A2
Figure 33. Bipolar Output Operation
R4
R2
R1
Bipolar Output Operation
VO = 1mV × Digital Code ×
–REFOUT ×
× 1+
Although the DAC8562 has been designed for single supply op-
eration, bipolar operation is achievable using the circuit illus-
trated in Figure 33. The circuit uses a single supply, rail-to-rail
OP295 op amp and the DAC’s internal +2.5 V reference to gen-
erate the –2.5 V reference required to level-shift the DAC out-
put voltage. The circuit has been configured to provide an
output voltage in the range –5 V ≤ VOUT ≤ +5 V and is coded in
complementary offset binary. Although each DAC LSB corre-
sponds to 1 mV, each output LSB has been scaled to 2.44 mV.
Table IV provides the relationship between the digital codes and
output voltage.
R3 + R4
R2
R1
For the ±2 5 V output range and the circuit values shown in the
table, the transfer equation becomes:
VO = 1. 22 mV × Digital Code – 2.5V
The transfer function of the circuit is given by:
Similarly, for the ±5 V output range, the transfer equation be-
comes:
R4
R1
R4
R2
VO = −1mV × Digital Code ×
+ 2.5 ×
VO = 2.44 mV × Digital Code – 5V
Note that, for ±5 V output voltage operation, R5 is required as a
pull-down for REFOUT. Or, REFOUT can be buffered by an
op amp configured as a follower that can source and sink cur-
rent.
and, for the circuit values shown, becomes:
VO = –2.44 mV × Digital Code + 5V
+5V
Table IV. Bipolar Code Table
0.1µF
Hexadecimal Number
in DAC Register
Decimal Number
in DAC Register
Analog Output
Voltage (V)
R2
20
V
DD
FFF
801
800
7FF
000
4095
2049
2048
2047
0
–4 9976
–2.44E–3
0
+2.44E–3
+5
R1
+5V
8
14
13
REFOUT
DATA
R5
2
3
4.99kΩ
DAC-8562
A1
V
1
O
CE
16
15
4
R3
V
CLR
OUT
–5V
AGND
12
DGND
10
To maintain monotonicity and accuracy, R1, R2, R4, R5, and
R6 should be selected to match within 0.01% and must all be of
the same (preferably metal foil) type to assure temperature coef-
ficient matching. Mismatching between R1 and R2 causes offset
and gain errors while an R4 to R1 and R2 mismatch yields gain
errors.
R4
A1 = 1/2 OP-295
V
OUT
RANGE
±2.5V
±5V
R1
10k
10k
R2
10k
20k
R3
R4
10k
10k
15.4k + 274
43.2k + 499
For applications that do not require high accuracy, the circuit il-
lustrated in Figure 34 can also be used to generate a bipolar
output voltage. In this circuit, only one op amp is used and no
potentiometers are used for offset and gain trim The output
voltage is coded in offset binary and is given by:
Figure 34. Bipolar Output Operation Without
Trim Version 1
REV. A
–11–
ADI [ ADI ]
