AD587
NEGATIVE REFERENCE VOLTAGE FROM AN AD587
The AD587 can be used to provide a precision –10.000 V output
as shown in Figure 11. The +V
IN
pin is tied to at least a +3.5 V
supply, the output pin is grounded, and the AD587 ground pin is
connected through a resistor, R
S
, to a –15 V supply. The –10 V
output is now taken from the ground pin (Pin 4) instead of
V
OUT
. It is essential to arrange the output load and the supply
resistor R
S
so that the net current through the AD587 is between
2.5 mA and 10.0 mA. The temperature characteristics and long-
term stability of the device will be essentially the same as that of
a unit used in the standard +10 V output configuration.
3.5V
→
26V
2
V
IN
V
OUT
6
The AD587 can also be used as a precision reference for multi-
ple DACs. Figure 13 shows the AD587, the AD7628 dual DAC,
and the AD712 dual op amp hooked up for single-supply opera-
tion to produce 0 V to –10 V outputs. Because both DACs are
on the same die and share a common reference and output
op amps, the DAC outputs will exhibit similar gain TCs.
+15V
+15V
0.1 F
V
IN
V
OUT
V
REFA
RFB A
OUT A
DAC A
DATA
INPUTS
18
AD587
GND
DB0
DB7
DAC B
DGND
AGND
V
OUT
A =
0 TO – 10V
AD7628
RFB B
OUT B
AD712
V
REFB
AD587
GND
4
1nF
←
I
L
R
S
2.5mA <
–15V
V
OUT
B =
0 TO – 10V
–10V
Figure 13. AD587 as a 10 V Reference for a CMOS Dual DAC
Precision Current Source
5V
– I
L
< 10mA
R
S
Figure 11. AD587 as a Negative 10 V Reference
USING THE AD587 WITH CONVERTERS
The design of the AD587 allows it to be easily configured as a
current source. By choosing the control resistor R
C
in Figure 14,
the user can vary the load current from the quiescent current
(2 mA typically) to approximately 10 mA.
+V
IN
2
V
IN
V
OUT
6
R
C
500
MIN
I
L
=
10V
+ I
BIAS
R
C
The AD587 is an ideal reference for a wide variety of 8-, 12-,
14-, and 16-bit ADCs and DACs. Several representative examples
follow.
10 V Reference with Multiplying CMOS DACs or ADCs
The AD587 is ideal for applications with 10-bit and 12-bit
multiplying CMOS DACs. In the standard hookup, as shown in
Figure 12, the AD587 is paired with the AD7545 12-bit multi-
plying DAC and the AD711 high speed BiFET op amp. The
amplifier DAC configuration produces a unipolar 0 V to –10 V
output range. Bipolar output applications and other operating
details can be found in the individual product data sheets.
+15V
+15V
0.1 F
V
IN
C1
33pF
V
DD
V
REF
10k
R
FB
OUT1
R2
+15V
0.1 F
AD587
GND
4
Figure 14. Precision Current Source
AD587
V
OUT
TRIM
GND
AD711K
AGND
DGND
0.1 F
V
OUT
0 TO
–
10V
AD7545K
DB11–DB0
–15V
Figure 12. Low Power 12-Bit CMOS DAC Application
REV. F
–7–
AD [ ANALOG DEVICES ]
