AD7545

–7–

REV. A

A1

R1

10K

Ω

CMOS DATA BUS

C1

33pF

AD544L

AD544J

A2

R5

20k

Ω

R3

10k

Ω

R6

5k

Ω

+2V

R2

2k

Ω

1

2

8

4

R4

33.3k

Ω

AD7545

18

19

20

1

2

DB10–DB0

OUT1

AGND

4

MSB

3

DGND

AD584J

+5V

Figure 10. Single Supply “Bipolar” Twos Complement

D/A

Converter

MICROPROCESSOR INTERFACING OF THE AD7545

The AD7545 can directly interface to both 8- and 16-bit micro-

processors via its 12-bit wide data latch using standard CS and

WR control signals.

A typical interface circuit for an 8-bit processor is shown in

Figure 11. This arrangement uses two memory addresses, one

for the lower eight bits of data to the DAC and one for the up-

per four bits of data into the DAC via the latch.

4

4

LATCH

CS

WR

8

AD7545

CS

DB11

DB8

WR

DB7

DB0

8

ADDRESS BUS

8-BIT DATA BUS

ADDRESS

DECODE

CPU

A15

A0

WR

D7

D0

Figure 11. 8-Bit Processor to AD7545 Interface

Figure 12 shows an alternative approach for use with 8-bit

processors which have a full 16-bit wide address bus such as

6800, 8080, Z80 This technique uses the 12 lower address lines

of the processor address bus to supply data to the DAC, thus

each AD7545 connected in this way uses 4k bytes of address

locations. Data is written to the DAC using a single memory

write instruction. The address field of the instruction is orga-

nized so that the lower 12 bits contain the data for the DAC and

the upper 4 bits contain the address of the 4k block at which the

DAC resides.

12

AD7545

CS

DB11

DB0

WR

16-BIT ADDRESS BUS

DATA BUS

ADDRESS

DECODE

CPU

A15

A0

WR

D7

D0

4

Figure 12. Connecting the AD7545 to 8-Bit Processors via

the Address Bus

SUPPLEMENTAL APPLICATION MATERIAL

For further information on CMOS multiplying D/A converters

the reader is referred to the following texts:

Application Guide to CMOS Multiplying D/A converters

available from Analog Devices, Publication Number G479.

Gain Error and Gain Temperature Coefficient of CMOS

Multiplying DACS—Application Note, Publication Number

E630–10–6/81 available from Analog Devices.