REV. B

ADDAC80/ADDAC85/ADDAC87

–11–

VOLTAGE OUTPUT MODELS

Internal scaling resistors provided in the ADDAC80 may be

connected to produce bipolar output voltage ranges of

±10 V,

±5 V or ±2.5 V or unipolar output voltage ranges of 0 V to +5 V

or 0 V to +10 V (see Figure 9).

REF

INPUT

TO REF

CONTROL

CIRCUIT

FROM

WEIGHTED

RESISTOR

NETWORK

SUMMING

JUNCTION

6.3k

5k

5k

18

20

16

+

–

OUTPUT

COM

BIPOLAR

OFFSET

21

15

19

17

Figure 9. Output Amplifier Voltage Range Scaling Circuit

Gain and offset drift are minimized in the ADDAC80 because

of the thermal tracking of the scaling resistors with other device

components. Connections for various output voltage ranges are

shown in Table III. Settling time is specified for a full-scale

range change: 4 s for a 10 k

Ω feedback resistor; 3 s for a 5 kΩ

feedback resistor when using the compensation capacitor shown

in Figure 3a.

The equivalent resistive scaling network and output circuit of

resistors are required to produce exactly 0 V to –2 V or

± 1 V

output. TCR of these resistors should be

±100 ppm/°C or less

to maintain the ADDAC80 output specifications. If exact output

ranges are not required, the external resistors are not needed.

17

TO REF CONTROL CIRCUIT

6.3k

3k

2k

19

20

16

18

REF IN

5k

15

Figure 10. Internal Scaling Resistors

6.3k

BIPOLAR OFFSET

REFERENCE

INPUT

COMMON

REFERENCE OUT

6.6k

V

TO REF

CONTROL

CIRCUIT

17

16

I

0 TO 2mA

6.3V

24

21

15

+

–

Figure 11. ADDAC80 Current Model Equivalent Output Circuit

Internal resistors are provided to scale an external op amp or to

configure a resistive load to offer two output voltage ranges of

±1 V

°C) are an

integral part of the ADDAC80 and maintain gain and bipolar

offset drift specifications. If the internal resistors are not used, exter-

±25 ppm/°C or

less to minimize drift. This will typically add

±50 ppm/°C + the

Table III. Output Voltage Range Connections, Voltage Model ADDAC80

Output

Digital

Connect

Connect

Connect

Connect

Range

Input Codes

Pin 15 to

Pin 17 to

Pin 19 to

Pin 16 to

±10 V

COB or CTC

19

20

15

24

±5 V

COB or CTC

18

20

NC

24

±2.5 V

COB or CTC

18

20

20

24

0 V to 10 V

CSB

18

21

NC

24

0 V to 5 V

CSB

18

21

20

24

0 V to 10 V

CCD

19

NC

15

24

NC = No Connect

DRIVING A RESISTIVE LOAD UNIPOLAR

VmA

kR

kR

OUT

L

L

=

×

+









–

.

.

2

66

66

Ω

Ω

(1)

Ω and V

To achieve specified drift, connect the internal scaling resistor

0 TO

2mA

CURRENT CONTROLLED

BY DIGITAL INPUT

6.6k

968

COMMON

+

–

15

18

21

Figure 12. Equivalent Circuit ADDAC80-CBI-I Connected

for Unipolar Voltage Output with Resistive Load