Datasheet
AD7839
–8–
REV. 0
Unipolar Configuration
Figure 11 shows the AD7839 in the unipolar binary circuit
configuration. The V
REF
(+) input of the DAC is driven by the
AD586, a +5 V reference. V
REF
(–) is tied to ground. Table II
gives the code table for unipolar operation of the AD7839.
Other suitable references include the REF02, a precision +5 V
reference, and the REF195, a low dropout, micropower preci-
sion +5 V reference.
AD7839*
V
DD
V
CC
V
REF
(+)
V
OUT
DUTGND
GND
V
SS
V
REF
(–)
SIGNAL
GND
–15V
V
OUT
(0 TO +10V)
+5V+15V
AD586
R1
10kV
2
6
5
4
8
C1
1mF
SIGNAL
GND
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 11. Unipolar +10 V Operation
Offset and gain may be adjusted in Figure 11 as follows: To
adjust offset, disconnect the V
REF
(–) input from 0 V, load the
DAC with all 0s and adjust the V
REF
(–) voltage until V
OUT
= 0 V.
For gain adjustment, the AD7839 should be loaded with all 1s
and R1 adjusted until V
OUT
= 2 V
REF
(+) – 1 LSB = 10 V(8191/
8192) = 9.99878 V.
Many circuits will not require these offset and gain adjustments.
In these circuits R1 can be omitted. Pin 5 of the AD586 may be
left open circuit and Pin 2 (V
REF
(–)) of the AD7839 tied to 0 V.
Table II. Code Table for Unipolar Operation
Binary Number in DAC Register Analog Output
MSB␣␣␣␣␣␣␣␣ LSB (V
OUT
)
1 1111 1111 1111 2 V
REF
(8191/8192) V
1 0000 0000 0000 2 V
REF
(4096/8192) V
0 1111 1111 1111 2 V
REF
(4095/8192) V
0 0000 0000 0001 2 V
REF
(1/8192) V
0 0000 0000 0000 0 V
NOTES
V
REF
= V
REF
(+); V
REF
(–) = 0 V for unipolar operation.
For V
REF
(+) = +5 V, 1 LSB = +10 V/2
13
= +10 V/8192 = 1.22 mV.
Bipolar Configuration
Figure 12 shows the AD7839 set up for ±10 V operation. The
AD588 provides precision ±5 V tracking outputs that are fed to
the V
REF
(+) and V
REF
(–) inputs of the AD7839. The code table
for bipolar operation of the AD7839 is shown in Table III.
In Figure 12, full-scale and bipolar zero adjustments are pro-
vided 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.
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
= 10(4095/4096) V = 9.997559 V.
When bipolar-zero and full-scale adjustment are not needed, R2
and R3 can be omitted. Pin 12 on the AD588 should be con-
nected to Pin 11 and Pin 5 should be left floating.
AD7839*
V
DD
V
CC
V
REF
(+)
V
OUT
DUTGND
GND
V
SS
V
REF
(–)
SIGNAL
GND
–15V
V
OUT
(–10V TO +10V)
+5V+15V
*ADDITIONAL PINS OMITTED FOR CLARITY
R1
39kV
C1
1mF
R2
100kV
R3
100kV
AD588
46
2
3
1
14
15
16
7
9
5
10
11
12 8 13
Figure 12. Bipolar
±
10 V Operation
Table III. Code Table for Bipolar Operation
Binary Number in DAC
Register Analog Output
MSB LSB (V
OUT
)
1 1111 1111 1111 2[V
REF
(–) + V
REF
(8191/8192)] V
1 0000 0000 0001 2[V
REF
(–) + V
REF
(4097/8192)] V
1 0000 0000 0000 2[V
REF
(–) + V
REF
(4096/8192)] V
0 1111 1111 1111 2[V
REF
(–) + V
REF
(4095/8192)] V
0 0000 0000 0001 2[V
REF
(–) + V
REF
(1/8192)] V
0 0000 0000 0000 2[V
REF
(–)] V
NOTES
V
REF
= (V
REF
(+) – V
REF
(–)).
For V
REF
(+) = +5 V, and V
REF
(–) = –5 V, V
REF
= 10 V, 1 LSB = 2 V
REF
V/2
13
=
20 V/8192 = 2.44 mV.
CONTROLLED POWER-ON OF THE OUTPUT STAGE
A block diagram of the output stage of the AD7839 is shown in
Figure 13. It is capable of driving a load of 5 kΩ in parallel with
50 pF. G
1
to G
6
are transmission gates used to control the
power on voltage present at V
OUT
. On power up G
1
and G
2
are
also used in conjunction with the CLR input to set V
OUT
to the
user defined voltage present at the DUTGND pin. When CLR
is taken back high, the DAC outputs reflect the data in the DAC
registers.
G
1
G
2
G
4
G
3
G
6
G
5
DUTGND
V
OUT
R
R = 60kV
14kV
DAC
Figure 13. Block Diagram of AD7839 Output Stage