Datasheet
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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
DAC7634
Reset DAC Registers
Chips Select
Serial Data Out
Serial Data In
Clock
Load DAC Registers
Load
NC = No Connection
–2.5V to +2.5V
–2.5V to +2.5V
–2.5V to +2.5V
–2.5V to +2.5V
+2.5V
+2.5V
–2.5V
–2.5V
+5V
+5V
–5V
–5V
+5V
+
+
1 µF
1 µF
0.1 µF
0.1 µF
0.1 µF1 µF
ANALOG OUTPUTS
DAC7634
SBAS134B – JULY 2004 – REVISED DECEMBER 2005
Figure 50. Basic Dual-Supply Operation of the DAC7634
converter with a 2.5 V full-scale range has a 1-LSB
value of 38 µV. With a load current of 1 mA, series
wiring and connector resistance of only 40 m Ω (R
W2
)
When V
SS
= –5V (dual supply operation), the output
causes a voltage drop of 40 µV, as shown in
amplifier can swing to within 2.25 V of the supply
Figure 51 . To understand what this means in terms of
rails, specified over the –40°C to 85°C temperature
a system layout, the resistivity of a typical 1-ounce
range. When V
SS
= 0 V (single-supply operation), and
copper-clad printed-circuit board is 1.2 m Ω per
with R
LOAD
also connected to ground, the output can
square. For a 1-mA load, a 10-mil wide printed-circuit
swing to ground. Care must also be taken when
conductor 600 mil long results in a voltage drop of 30
measuring the zero-scale error when V
SS
= 0 V.
µV.
Because the output voltage cannot swing below
The DAC7634 offers a force and sense output
ground, the output voltage may not change for the
configuration for the high open-loop gain output
first few digital input codes (0000
H
, 0001
H
, 0002
H
,
amplifier. This feature allows the loop around the
etc.) if the output amplifier has a negative offset. At
output amplifier to be closed at the load (as shown in
the negative limit of –2 mV, the first specified output
Figure 51 ), thus ensuring an accurate output voltage.
starts at code 0040
H
.
Due to the high accuracy of these D/A converters,
system design problems such as grounding and
contact resistance become important. A 16-bit
18