1
2
3
4
5
6
7
8
9
DB15 (MSB)
DB14
DB13
DB12
DB11
DB10
DB9
NC 48
NC 47
NC 46
NC 45
V
OUTA Sense 44
–10V to +10V
VOUT
A
43
VREFL AB Sense 42
VREFL AB 41
–10V
+10V
DB8
Data
Bus
DB7
VREFH AB 40
10 DB6
VREFH AB Sense 39
VOUTB Sense 38
11 DB5
–10V to +10V
–10V to +10V
12 DB4
VOUT
OUTC Sense 36
VOUT
35
B
37
DAC7744
13 DB3
V
14 DB2
C
15 DB1
VREFH CD Sense 34
VREFH CD 33
+10V
–10V
16 DB0 (LSB)
17 RSTSEL
18 RST
19 LOADDACS
20 R/W
+5V
Reset DACs
VREFL CD 32
V
REFL CD Sense 31
VOUTD Sense 30
Load DAC Registers
READ/WRITE
–10V to +10V
VOUT
D
29
–15V
+15V
+5V
21 A1
VSS 28
AGND 27
VCC 26
Address
0.1µF
1µF
1µF
+
+
22 A0
Chip Select
23 CS
0.1µF
0.1µF
24 DGND
VDD 25
NC = No Connection
+
1µF
FIGURE 3. Basic Dual-Supply Operation of the DAC7744.
ANALOG OUTPUTS
allows the loop around the output amplifier to be closed at
the load, thus ensuring an accurate output voltage, as shown
in Figure 4.
When VSS = –15V (dual supply operation), the output ampli-
fier can swing to within 4V of the supply rails, guaranteed
over the –40°C to +85°C temperature range. With VSS = 0V
(single-supply operation), and with RLOAD also connected to
ground, the output can swing to ground. Care must also be
taken when measuring the zero-scale error when VSS = 0V.
Since the output voltage cannot swing below ground, the
output voltage may not change for the first few digital input
codes (0000H, 0001H, 0002H, etc.), if the output amplifier has
a negative offset. At the negative limit of –5mV, the first
specified output starts at code 0021H.
DAC7744
NC 48
NC 47
NC 46
NC 45
RW1
V
OUTA Sense 44
OUTA 43
REFL AB Sense 42
REFL AB 41
REFH AB 40
REFH AB Sense 39
OUTB Sense 38
OUTB 37
RW2
VOUT
RLOAD
V
V
Due to the high accuracy of these D/A converters, 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 (RW2) 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.
V
+V
V
+10V
V
RW1
V
V
RW2
VOUT
RLOAD
FIGURE 4. Analog Output Closed-Loop Configuration
(1/2 DAC7744). RW represents wiring resis-
tances.
The DAC7744 offers a force and sense output configuration
for the high open-loop gain output amplifiers. This feature
®
17
DAC7744
TI [ TEXAS INSTRUMENTS ]
