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 sup-
ply resistor R
S
so that the net current through the AD587 is be-
tween 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 mul-
tiple DACs. Figure 13 shows the AD587, the AD7628 dual
DAC and the AD712 dual op amp hooked up for single supply
operation 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.
AD587
GND
4
1nF
←
I
L
R
S
2.5mA <
–15V
5V
–I
L
<10mA
R
S
–10V
Figure 13. AD587 as a 10 V Reference for a CMOS Dual
DAC
PRECISION CURRENT SOURCE
Figure 11. AD587 as a Negative 10 V Reference
USING THE AD587 WITH CONVERTERS
The AD587 is an ideal reference for a wide variety of 8-, 12-,
14- and 16-bit A/D and D/A converters. Several representative
examples follow.
10 V REFERENCE WITH MULTIPLYING CMOS D/A OR
A/D 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,
you 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
500Ω
MIN
I
L
=
10V
+ I
BIAS
R
C
The AD587 is ideal for applications with 10- and 12-bit multi-
plying CMOS D/A converters. In the standard hookup, as
shown in Figure 12, the AD587 is paired with the AD7545
12-bit multiplying 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 on the individual product data
sheets.
AD587
GND
4
Figure 14. Precision Current Source
Figure 12. Low Power 12-Bit CMOS DAC Application
REV. D
–7–
AD [ ANALOG DEVICES ]
