DAC8562

REV. A

–11–

15

16

DGND

AGND

DATA

DAC-8562

13

10µF

0.1µF

–5V

+5V

10

CE

CLR

20

12

14

REFOUT

R1

10k

R2

12.7k

–2.5V

2

3

4

8

A1

+5V

–5V

1

P2

500

FULL SCALE

ADJUST

R4

23.7k

P1

10k

ZERO SCALE

ADJUST

R3

247k

R5

10k

R6

10k

6

5

A2

7

A1, A2 = 1/2 OP-295

Ω

Ω

Ω

Ω

Ω

Ω

Ω

Figure 33. Bipolar Output Operation

Bipolar Output Operation

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

≤ V

OUT

≤ +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.

The transfer function of the circuit is given by:

V

R4

R1









+ 2.5 × R4

R2









and, for the circuit values shown, becomes:

V

Table IV. Bipolar Code Table

Hexadecimal Number

Decimal Number

Analog Output

in DAC Register

in DAC Register

Voltage (V)

FFF

4095

–4 9976

801

2049

–2.44E–3

800

2048

0

7FF

2047

+2.44E–3

000

0

+5

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.

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:

V

R4

R3

+ R4









× 1+

R2

R1









– REFOUT

×

R2

R1









For the

±2 5 V output range and the circuit values shown in the

table, the transfer equation becomes:

V

Similarly, for the

±5 V output range, the transfer equation be-

comes:

V

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.

15

16

DATA

DAC-8562

13

CE

CLR

DGND

AGND

10

12

0.1µF

+5V

20

14

REFOUT

R1

R5

4.99k

A1 = 1/2 OP-295

R4

R3

R2

2

3

4

8

A1

+5V

–5V

1

RANGE

±2.5V

±5V

R1

10k

10k

R2

10k

20k

R3

10k

10k

R4

15.4k + 274

43.2k + 499

Ω

Figure 34. Bipolar Output Operation Without

Trim Version 1