AD1865 Analog Devices, AD1865 Datasheet - Page 9

• Manufacturer Part Number: AD1865
• Description: Complete Dual 18-Bit 16 x Fs Audio DAC
• Manufacturer: Analog Devices

VOICE 1 LOAD
VOICE 2 LOAD
VOICE 3 LOAD
+5V ANALOG
–5V ANALOG
REV. 0
MULTICHANNEL DIGITAL KEYBOARD DESIGN
Figure 11 illustrates how to cascade AD1865’s 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 ap-
propriate DAC is updated. For example, after the 18-bits repre-
senting 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.
SUPPLY
SUPPLY
CLOCK
COMMON
ANALOG
DATA
OUTPUT
VOICE 1
10
12
11
1
2
3
4
5
6
7
8
9
+V
–V
MSB
AGND
SJ
TRIM
I
R
V
DR
LR
CLK
OUT
OUT
F
S
L
AD1865
Figure 11. Cascaded AD1865s in a Multichannel Keyboard Instrument
AGND
DGND
TRIM
V
MSB
I
+V
OUT
OUT
NC
R
DL
LL
SJ
S
F
24
23
22
20
19
18
17
16
15
14
13
21
OUTPUT
VOICE 2
VOICE 3
OUTPUT
10
11
12
1
2
3
4
5
6
7
8
9
–V
MSB
SJ
+V
I
AGND
R
V
DR
LR
TRIM
CLK
OUT
OUT
F
S
L
AD1865
–9–
DGND
AGND
TRIM
V
MSB
I
+V
OUT
OUT
NC
SJ
R
DL
LL
S
In this application, the advantages of choosing the AD1865 are
clear. Its flexible digital interface allows the clock and data to be
shared among all DACs. This reduces PC board area require-
ments and also simplifies the actual layout of the board. The low
power requirements of the AD1865 (approximately 225 mW) is
an advantage in a multiple DAC system where any power advan-
tage is multiplied by the number of DACs used. The AD1865
requires no external components, simplifying the design, reduc-
ing the total number of components required and enhancing
reliability.
F
24
23
22
21
20
19
18
17
16
15
14
13
OUTPUT
VOICE 4
OUTPUT
VOICE 5
10
11
12
1
2
3
4
5
6
7
8
9
–V
MSB
SJ
+V
I
AGND
R
V
DR
LR
TRIM
CLK
OUT
F
OUT
AD1865
S
L
DGND
AGND
TRIM
V
MSB
I
+V
OUT
OUT
NC
SJ
R
DL
LL
S
F
24
23
22
21
20
19
18
17
16
15
14
13
OUTPUT
VOICE 6
AD1865
+5V DIGITAL SUPPLY
VOICE 6 LOAD
VOICE 5 LOAD
VOICE 4 LOAD
DIGITAL COMMON