DAC7741Y Burr-Brown Corporation, DAC7741Y Datasheet - Page 16

• Manufacturer Part Number: DAC7741Y
• Description: 16-Bit/ Single Channel DIGITAL-TO-ANALOG CONVERTER With Internal Reference and Parallel Interface
• Manufacturer: Burr-Brown Corporation

TABLE IV. Nominal V
OFFSET ADJUSTMENT
Offset adjustment is accomplished by introducing a small
current into the summing junction (SJ) of the DAC7741. The
voltage at SJ, or V
tion of the DAC7741. See Table IV for the required pin
strapping for a given configuration and the nominal values of
V
The current level required to adjust the DAC7741 offset can
be created by using a potentiometer divider as shown in
Figure 7. Another alternative is to use a unipolar DAC in
order to apply a voltage, V
current range applied to SJ will ensure offset adjustment
coverage of the 0.1% maximum offset specification of the
DAC7741.
When in a unipolar configuration (V
resistor, R
a 0V to 10V V
configurations, V
( 5V range), and circuit values chosen to match those given
in Table V will provide symmetrical offset adjust. Please refer
to Figure 7 for component configuration.
TABLE V. Recommended External Component Values for
Figure 8 illustrates the typical and minimum offset adjustment
ranges provided by forcing a current at SJ for a given output
voltage configuration.
GAIN ADJUSTMENT
When using the internal reference of the DAC7741, gain
adjustment is performed by adjusting the internal refer-
ence voltage via the reference adjust pin, REFADJ. The
effect of a reference voltage change on the gain of the
DAC output can be seen in the generic equation (for
unipolar configuration):
where N is represented in decimal format and ranges from 0
to 65535.
REFADJ can be driven by a low impedance voltage source
such as a unipolar, 0V to +10V DAC or a potentiometer (less
16
OUTPUT
CONFIGURATION
0V to +10V
–10V to +10V
–5V to +5V
REFERENCE
CONFIGURATION CONFIGURATION R
Internal
Reference
External
Reference
NOTE: (1) Voltage measured at V
SJ
for each output range.
S
Symmetrical Offset Adjustment (V
, is needed for symmetrical offset adjustment with
OADJ
–V
SJ
–V
V
–10V to +10V
R
REF
10K
10K
10K
0V to +10V
–5V to +5V
0V to V
POT2
OUT
OUTPUT
SJ
is either +3.333v ( 10V range) or +1.666V
REF
range. When in one of the two bipolar
/2 to V
SJ
, is dependent on the output configura-
to V
= V
vs. V
REF
20K
REF
REF
5K
R
0
REFIN
1
SJ
OADJ
/2 to AGND to V
OUT
for a given configuration.
to AGND to V
to V
to V
and Reference Configuration.
• (N/65536)
, to the resistor R
2.5M
1.5M
OFFSET
1M
R
NC
NC
S
REF
REF
PIN STRAPPING
SJ
RANGE
to V
to V
RFB1
= 5V), only a single
2.2 A
1.7 A
NC
NC
2 A
I
SJ
OUT
OUT
OUT
OUT
REF
to V
to V
to V
to V
to V
to V
RFB2
ADJUSTMENT
= 10V).
OUT
OUT
OUT
OUT
OUT
OUT
NOMINAL
S
OFFSET
. A 2uA
25mV
55mV
21mV
+3.333V
+1.666V
V
V
V
V
+5V
REF
REF
REF
SJ
(1)
/2
/3
/6
www.ti.com
than 100k ) as shown in Figure 7. Since the input imped-
ance of REFADJ is typically 50k , the smaller the resistance
of the potentiometer, the more linear the adjustment will be.
A 10k
ence adjustment is of concern.
FIGURE 8. Offset Adjustment Transfer Characteristic.
When the DAC7741 internal reference is not used, gain
adjustments can be made via trimming the external refer-
ence applied to the DAC at REF
through using a potentiometer, unipolar DAC, or other means
of precision voltage adjustment to control the voltage pre-
sented to the DAC7741 by the external reference. Figure 9
and Table VI summarize the range of adjustment of the
internal reference via REFADJ.
FIGURE 9. Internal Reference Adjustment Transfer Charac-
TABLE VI. Minimum Internal Reference Adjustment Range.
NOTE: "NC" is "Not Connected"
VOLTAGE AT REFADJ
–25
–50
–10
–20
–30
–40
REFADJ = 5V or NC
50
25
40
30
20
10
0
0
potentiometer is suggested if linearity of the refer-
–2
REFADJ = 10V
REFADJ = 0V
0
0V to 10V and –5V to +5V
V
typ
min (75% of typ)
Adjustment Range
Minimum REF
teristic.
OUT
Configuration
2
–1
typ
Adjustment Range
(1)
Typical REF
OUT
OFFSET ADJUST RANGE
REF
–10V to +10V V
Configuration
OUT
4
REFADJ (V)
min (75% of typ)
I
ADJUST RANGE
SJ
IN
OUT
0
( A)
. This can be accomplished
OUT
6
REF
10V – 25mV (max)
10V + 25mV (min)
OUT
10V
1
VOLTAGE
DAC7741
8
SBAS248A
10
2