Datasheet

AD7834/AD7835
Rev. D | Page 16 of 28
BIPOLAR CONFIGURATION
In Figure 20, full-scale and bipolar zero adjustments are
provided by varying the gain and balance on the
AD588. R2
varies the gain on the AD588 while R3 adjusts the offset of both
the +5 V and –5 V outputs together with respect to ground.
+15V
+5V
V
OUT
(–5V TO +5V)
V
CC
6
3
4
C1
1μF
AGND
DGND
V
DD
V
OUT
V
REF
(+)
V
REF
(–)
V
SS
–15V
1
ADDITIONAL PINS OMITTED FOR CLARITY
R2
100kΩ
AD7834/
AD7835
1
SIGNAL
GND
2
14
15
16
12 8
13
11
10
5
9
7
R3
100kΩ
R1
39kΩ
1
AD588
01006-020
For bipolar-zero adjustment, the DAC is loaded with
1000 . . . 0000 and R3 is adjusted until V
OUT
= 0 V. Full scale
is adjusted by loading the DAC with all 1s and adjusting R2
until V
OUT
= 5(8191/8192) V = 4.99939 V.
When bipolar zero and full-scale adjustment are not needed, R2
and R3 are omitted. Pin 12 on the
AD588 should be connected to
Pin 11, and Pin 5 should be left floating.
Figure 20. Bipolar ±5 V Operation
Figure 20 shows the AD7834/AD7835 setup for ±5 V operation.
The
AD588 provides precision ±5 V tracking outputs that are
fed to the V
REF
(+) and V
REF
(−) inputs of the AD7834/AD7835.
The code table for bipolar operation of the AD7834/AD7835 is
shown in
Tabl e 13.
Table 13. Code Table for Bipolar Operation
1, 2
Binary Number in DAC Latch
MSB LSB Analog Output (V
OUT
)
V
REF
(−) + V
REF
(16383/16384) V
11 1111 1111 1111
V
REF
(−) + V
REF
(8193/16384) V
10 0000 0000 0001
V
REF
(−) + V
REF
(8192/16384) V
10 0000 0000 0000
V
REF
(−) + V
REF
(8191/16384) V
01 1111 1111 1111
V
REF
(−) + V
REF
(1/16384) V
00 0000 0000 0001
V
REF
(−) V
00 0000 0000 0000
1
V
REF
= V
REF
(+) – V
REF
(−).
2
For V
REF
(+) = +5 V and V
REF
(−) = –5 V, 1 LSB = 10 V/2
14
= 10 V/16384 = 610 μV.