Datasheet
DAC7734
17
SBAS138A
www.ti.com
FIGURE 3. Basic Dual-Supply Operation of the DAC7734.
ANALOG OUTPUTS
When V
SS
= –15V (dual-supply operation), the output am-
plifier can swing to within 4V of the supply rails, ensured
over the –40°C to +85°C temperature range. When
V
SS
= 0V (single-supply operation), and with R
LOAD
also
connected to ground, the output can swing to ground. Care
must also be taken when measuring the zero-scale error
when V
SS
= 0V. Since the output voltage cannot swing
below ground, the output voltage may not change for the
first few digital input codes (0000
H
, 0001
H
, 0002
H
, etc.) if
the output amplifier has a negative offset. At the negative
limit of –5mV, the first specified output starts at code 0021
H
.
Due to the high accuracy of these DACs, system design
problems such as grounding and contact resistance become
very important. A 16-bit converter with a 10V full-scale
range has a 1LSB value of 152µV. With a load current of
1mA, series wiring and connector resistance of only 150mΩ
(R
W2
) will cause a voltage drop of 150µV, as shown in
Figure 4. To understand what this means in terms of a
system layout, the resistivity of a typical 1-ounce copper-
clad printed circuit board is 1/2 mΩ per square. For a 1mA
load, a 20 milli-inch wide printed circuit conductor 6 inches
long will result in a voltage drop of 150µV.
The DAC7734 offers a force and sense output configuration
for the high open-loop gain output amplifier. This feature
allows the loop around the output amplifier to be closed at
the load (as shown in Figure 4), thus ensuring an accurate
output voltage.
FIGURE 4. Analog Output Closed-Loop Configuration
(1/2 DAC7734). R
W
represents wiring resis-
tances.
NC
NC
SDI
DGND
CLK
DGND
LDAC
DGND
LOAD
DGND
CS
DGND
SDO
DGND
RSTSEL
DGND
RST
DGND
NC
NC
DGND
DGND
V
DD
V
DD
V
OUT
A Sense
V
OUT
A
AGND
V
SS
V
REF
L AB Sense
V
REF
L AB
V
REF
H AB
V
REF
H AB Sense
V
OUT
B Sense
V
OUT
B
V
OUT
C Sense
V
OUT
C
V
REF
H CD Sense
V
REF
H CD
V
REF
L CD
V
REF
L CD Sense
V
OUT
D Sense
V
OUT
D
V
SS
V
SS
AGND
AGND
V
CC
V
CC
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
DAC7734
Reset DAC Registers
Chips Select
Serial Data Out
Serial Data In
Clock
Load DAC Registers
Load
NC = No Connection
–10V to +10V
–10V to +10V
–10V to +10V
–10V to +10V
+10.000V
+10.000V
–10.000V
–10.000V
+5V
+15V
0.1µF
1µF
1µF
+
0.1µF
0.1µF 1µF
–15V
–15V
+5V
+
+
V
OUT
A Sense
V
OUT
A
AGND
V
SS
V
REF
L AB Sense
V
REF
L AB
V
REF
H AB
V
REF
H AB Sense
V
OUT
B Sense
V
OUT
B
48
47
46
45
44
43
42
41
40
39
DAC7734
R
W1
R
W2
+10V
+V
V
OUT
R
W1
R
W2
V
OUT