AD1864

–9–

REV. A

AD1864

S

+V

L

–V

TRIM

MSB

SJ

DL

LL

DGND

AGND

OUT

V

OUT

I

OUT

I

OUT

V

TRIM

MSB

LR

CLK

DR

AGND

SJ

1

2

3

4

5

6

7

8

9

10

11

12

24

23

22

21

20

19

18

17

16

15

14

13

+5V ANALOG

SUPPLY

–5V ANALOG

SUPPLY

VOICE 1

OUTPUT

AD1864

S

+V

L

–V

TRIM

MSB

SJ

DL

LL

DGND

AGND

OUT

V

OUT

I

OUT

I

OUT

V

TRIM

MSB

LR

CLK

DR

AGND

SJ

1

2

3

4

5

6

7

8

9

10

11

12

24

23

22

21

20

19

18

17

16

15

14

13

AD1864

S

+V

L

–V

TRIM

MSB

SJ

DL

LL

DGND

AGND

OUT

V

OUT

I

OUT

I

OUT

V

TRIM

MSB

LR

CLK

DR

AGND

SJ

1

2

3

4

5

6

7

8

9

10

11

12

24

23

22

21

20

19

18

17

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13

VOICE 1 LOAD

ANALOG

COMMON

VOICE 3 LOAD

DATA

VOICE 2 LOAD

CLOCK

VOICE 2

OUTPUT

VOICE 3

OUTPUT

VOICE 4

OUTPUT

VOICE 5

OUTPUT

VOICE 6

OUTPUT

VOICE 6 LOAD

VOICE 5 LOAD

VOICE 4 LOAD

DIGITAL COMMON

–5V DIGITAL COMMON

+5V DIGITAL COMMON

Figure 12. Cascaded AD1864s in a Multichannel Keyboard Instrument

MULTICHANNEL DIGITAL KEYBOARD DESIGN

Figure 12 illustrates how to cascade AD1864s to add multiple

voices to an electronic musical instrument. In this example, the

data and clock signals are shared between all six DACs. As the

data representing an output for a specific voice is loaded, the

appropriate DAC is updated. For example, after the 18 bits

representing the next output value for Voice #4 is clocked out

on the data line, then “Voice 4 Load” is pulled low. This produces

a new output for Voice 4. Furthermore, all voices can be

returned to the same output by pulling all six load signals low.

In this application, the advantages of choosing the AD1864 are

clear. Its flexible digital interface allows the clock and data to

be shared among all DACs. This reduces printed circuit board

area requirements and also simplifies the actual layout of the

board. The low power requirement of the AD1864 (typically

215 mW) is an advantage in a multiple DAC system where its

power advantage is multiplied by the number of DACs used.

The AD1864 requires no external components, simplifying the

design, reducing the total number of components required and

enhancing reliability.

ADDITIONAL APPLICATIONS

Figures 13 through 16 show connection diagrams for the

AD1864 and a number of standard digital filter chips from

Yamaha, NPC and Sony. Figure 13 shows the SM5814AP

operating with pipelined data. Cophase operation is not

available with the SM5814AP in 18-bit mode. Figures 14

through 16 are all examples of cophase operation. Each

application operates at 8

× F

Rauch low-pass filters shown in Figure 11 can be used with all

of the applications shown in this data sheet. The AD711 single

op amp can also be used in these applications in order to ensure

maximum channel separation.