9

®

DAC813

FIGURE 5. Power Supply, Gain, and Offset Connections.

200

Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

28

27

26

25

24

23

22

21

20

19

18

17

16

15

1k

Ω

V

OUT

3M

Ω

1

2

3

4

5

6

7

8

9

10

11

12

13

14

28

27

26

25

24

23

22

21

20

19

18

17

16

15

1k

Ω

V

OUT

–V

CC

10k

to

100k

BIPOLAR

UNIPOLAR

(2)

(1) 10µF tantalum for

optimum settling

performance.

(2) Unipolar offset is

not necessary in most

applications and can

lead to noise pickup.

(3) Note that for the

ceramic package

the lid is connected

to –V

Ω

Ω

++

0.01µF

0.01µF

+V

CC

L

REF OUT

REF IN

CC

OUT

CC

V

20V Range

20V Range

BPO

ACOM

V

V

+V

V

–V

WR

LDAC

Reset

LMSB

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

DCOM

LLSB

(1)

0.01µF

(1)

0.01µF

0.01µF

L

REF OUT

REF IN

CC

OUT

CC

V

20V Range

20V Range

BPO

ACOM

V

V

+V

V

–V

WR

LDAC

Reset

LMSB

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

DCOM

LLSB

+V

CC

+V

CC

–V

CC

(3)

–V

CC

(3)

DAC813 features separate digital and analog power supply

returns to permit optimum connections for low noise and

high speed performance. It is recommended that both Ana-

log Common (ACOM, Pin 5) and Digital Common (DCOM,

Pin 16) be connected directly to a ground plane under the

package. If a ground plane is not used, connect the ACOM

and DCOM pins together close to the package. Since the

is also important to connect the load directly to the ACOM

pin. Refer to Figure 5.

The change in current in the Analog Common pin (ACOM,

OUTPUT RANGE CONNECTIONS

Internal scaling resistors provided in the DAC813 may be

connected to produce bipolar output voltage ranges of

±10V

and

±5V or unipolar output voltage range of 0 to +10V.

Refer to Figure 6.

The internal feedback resistors (25k

Ω) and the bipolar offset

resistor (24.9k

Ω) are trimmed to an absolute tolerance of

less than

±2%. Therefore, one can change the range by

adding a series resistor in various feedback circuit configu-

rations. For example, a 600

Ω resistor in series with the 20V

range terminal can be used to obtain a 20.48V (

±10.24V)

range (5mV LSB). A 7.98k

Ω resistor in series with the 10V

range connection (20V ranges in parallel) gives a 16.384V

(

±8.192V) bipolar range (4mV LSB). Gain drift will be

affected by the mismatch of the temperature coefficient of

the external resistor with the internal D/A resistors.

APPLICATIONS

MICROCOMPUTER BUS INTERFACING

The DAC813 interface logic allows easy interface to micro-

computer bus structures. The control signal is derived from

external device select logic and the I/O Write or Memory

Write (depending upon the system design) signals from the

microcomputer.

The latch enable lines LMSB, LLSB, and LDAC determine

which of the latches are selected. It is permissible to enable

two or more latches simultaneously, as shown in some of the

following examples.

The double-buffered latch permits data to be loaded into the

input latches of several DAC813s and later strobed into the

D/A latch of all D/As, simultaneously updating all analog

outputs. All the interface schemes shown below use a base

address decoder. If blocks of memory are used, the base

address decoder can be simplified or eliminated altogether.

8-BIT INTERFACE

The control logic of DAC813 permits interfacing to right-

justified data formats, illustrated in Figure 7. When a 12-bit

D/A converter is loaded from an 8-bit bus, two bytes of data

are required. Figure 8 illustrates an addressing scheme for

right-justified data. The base address is decoded from the

high-order address bits. A0 and A1 address the appropriate

ously transfers input latch data to the D/A latch. Addresses