5962-8982502PA Datasheet, PDF (10/12 Pages) Analog Devices – High Precision 10 V Reference

AD587
APPLICATIONS INFORMATION
USING THE AD587 WITH CONVERTERS
The AD587 is an ideal reference for a variety of 8-bit, 12-bit,
14-bit, and 16-bit ADCs and DACs. Several 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, shown in
Figure 18, 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
+V_IN
AD587
V_OUT
TRIM
GND
+15V
R2
0.1µF
10kΩ
V_DD
V_REF
R_FB
OUT1
AD7545 _AGND
DGND
C1 ^+15V
33pF _0.1µF
AD711
V_OUT
0V TO –10V
0.1µF
DB11 TO DB0
–15V
Figure 18. Low Power 12-Bit CMOS DAC Application
The AD587 can also be used as a precision reference for multi-
ple DACs. Figure 19 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 temperature
coefficients (TCs).
+15V
+V_IN
V_OUT
AD587
GND
0.1µF
+15V
V_REFA
RFB A
OUT A
DAC A
DATA
INPUTS
DB0 _AD7628
DB7
18
V_REFB
DAC B
AGND
RFB B
OUT B
DGND
AD712
V_OUTA =
0 TO –10V
V_OUTB =
0 TO –10V
Figure 19. AD587 as a 10 V Reference for a CMOS Dual DAC
Precision Current Source
The design of the AD587 allows it to be easily configured as a cur-
rent source. By choosing the control resistor (RC) via the equation
shown in Figure 20, 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}
AD587
GND
4
R_C
500Ω
MIN
10V
I_L = _RC + I_BIAS
Figure 20. Precision Current Source
Precision High Current Supply
For higher currents, the AD587 can easily be connected to a
power PNP or power Darlington PNP device. The circuits in
Figure 21 and Figure 22 can deliver up to 4 A to the load. The
0.1 μF capacitor is required only if the load has a significant
capacitive component. If the load is purely resistive, improved
high frequency supply rejection results can be obtained by
removing the capacitor.
+V_IN
220Ω
2N6285
0.1µF
2
+V_IN
AD587 ^{VOUT 6}
GND
4
10V
R_C
I_L = _RC + I_BIAS
Figure 21. Precision High Current Source
+V_IN
220Ω
2N6285
0.1µF
2
+V_IN
AD587 ^{VOUT 6}
GND
4
V_OUT
+10V @ 4A
Figure 22. Precision High Current Voltage Source
Rev. H | Page 10 of 12