ADDAC80 Analog Devices, ADDAC80 Datasheet - Page 12

• Manufacturer Part Number: ADDAC80
• Description: Complete Low Cost Hybrid 12-Bit D/A Converter 0 to +70 C
• Manufacturer: Analog Devices

ADDAC80/ADDAC85/ADDAC87
DRIVING A RESISTOR LOAD BIPOLAR
The equivalent output circuit for a bipolar output voltage range
is shown in Figure 13, R
where R
To achieve specified drift, connect the internal scaling resistors
(R
an external metal film resistor (R
output range of ± 1 V. In this configuration, with R
zero, the full scale range will be ± 0.874 V.
DRIVING AN EXTERNAL OP AMP
The current model ADDAC80 will drive the summing junction
of an op amp used as a current to voltage converter to produce
an output voltage. As seen in Figure 14,
where I
back resistor. Using the internal feedback resistors of the current
model ADDAC80 provides output voltage ranges the same as
the voltage model ADDAC80. To obtain the desired output
voltage range when connecting an external op amp, refer to
Table V and Figure 14.
Digital
Input Codes
CSB
COB or CTC ± 1 V
CCD
V
LI
V
OUT
) as shown in Table IV for the COB or CTC codes and add
OUT
OUT
L
= ±
=
CURRENT CONTROLLED
BY DIGITAL INPUT
max = 11.18 kΩ and V
I
is the ADDAC80 output current and R
1
OUT
mA
Output
Range
0 to –2 V 0.968
0 to ± 2 V 3
1mA
×



R
R
R
F
L
L
3.22k
×
+
L
3 22
3 22
.
.
= R
Internal
Resistance Resistance Connect
R
1.2
LI
k
k
LI
R
1.2k
Ω
Ω
(k )
LI
+ R
LS
OUT



) in series to obtain a full scale
LS
max = ± 2.5 V
15
20
21
. V
Table IV. Current Model/Resistive Load Connections
COMMON
OUT
1%
Metal Film
External
R
210 Ω
249 Ω
N/A
R
LS
LS
is determined by:
V
F
LS
OUT
is the feed-
+
equal to
–
Pin 15 to Pin 18 to
20
18
NC
(2)
(3)
R
LI
Connect
19 and R
19
21
Connections
OUTPUT LARGER THAN 20 V RANGE
For output voltage ranges larger than ± 10 V, a high voltage op
amp may be employed with an external feedback resistor. Use
I
unipolar voltage ranges (see Figure 15). Use protection diodes
when a high voltage op amp is used.
The feedback resistor, R
as low as possible. Using an external feedback resistor, overall
drift of the circuit increases due to the lack of temperature track-
ing between R
typically add 50 ppm/°C + R
OUT
FOR FAST SETTLING TIME
FOR OUTPUT VOLTAGE SWINGS UP TO 140V p-p
values of ± l mA for bipolar voltage ranges and –2 mA for
–
+
5k
LS
V
0 TO 2mA
0 TO 2mA
V
Connect Connect
15
I
6.3V
Pin 20 to Pin 16 to
R
NC
REF
I
F
LS
and the internal scaling resistor network. This will
5k
CBI
Reference
24
24
24
F
6.6k
, should have a temperature coefficient
6.3k
6.6k
F
drift to total drift.
17
16
15
21
24
19
18
15
21
Connect
Pin 17 to
Com (21)
15
NC
20V RANGE
10V RANGE
Bipolar Offset
AD509KH
171K
R
F
R
Between
Pin 18 and
Com (21)
Between
Pin 20 and
Com (21)
N/A
LS
V
V
OUT
OUT
A