AD587KQ Analog Devices Inc, AD587KQ Datasheet - Page 6

• Manufacturer Part Number: AD587KQ
• Manufacturer: Analog Devices Inc

Specifications of AD587KQ

• Fixed / Adjust / Prog: Precision
• Output Voltage (max): 10V
• Temperature Coefficient: 10ppm/°C
• Reference Voltage Accuracy (max): 5
• Line Regulation: 100uV/V
• Load Regulation: 100uV/mA
• Input Voltage (max): 36V
• Operating Temp Range: 0C to 70C
• Operating Temperature Classification: Commercial
• Mounting: Through Hole
• Pin Count: 8
• Package Type: CDIP
• Lead Free Status / Rohs Status: Not Compliant

AD587
THEORY OF OPERATION
The AD587 consists of a proprietary buried Zener diode
reference, an amplifier to buffer the output, and several high
stability thin-film resistors, as shown in Figure 3. This design
results in a high precision monolithic 10 V output reference
with initial offset of 5 mV or less. The temperature compensa-
tion circuitry provides the device with a temperature coefficient
of less than 5 ppm/°C.
A capacitor can be added at the NOISE REDUCTION pin
(Pin 8) to form a low-pass filter with R
contribution of the Zener to the circuit.
APPLYING THE AD587
The AD587 is simple to use in virtually all precision reference
applications. When power is applied to Pin 2 and Pin 4 is
grounded, Pin 6 provides a 10 V output. No external compo-
nents are required; the degree of desired absolute accuracy is
achieved simply by selecting the required device grade. The
AD587 requires less than 4 mA quiescent current from an
operating supply of 15 V.
Fine trimming may be desired to set the output level to exactly
10.000 V (calibrated to a main system reference). System cali-
bration may also require a reference voltage that is slightly
different from 10.000 V, for example, 10.24 V for binary
applications. In either case, the optional trim circuit shown in
Figure 4 can offset the output by as much as 300 mV with
minimal effect on other device characteristics.
REDUCTION
CAPACITOR
OPTIONAL
NOISE
NOTE
PINS 1, 3, AND 7 ARE INTERNAL TEST POINTS.
NO CONNECTIONS TO THESE POINTS.
1µF
Figure 4. Optional Fine Trim Configuration
C
N
+V
Figure 3. Functional Block Diagram
2
IN
8
REDUCTION
R
NOISE
REDUCTION
S
R
NOISE
GND
I
AD587
4
8
GND
+V
V
2
4
IN
IN
A1
R
TRIM
T
AD587
V
R
O
F
6
5
S
to reduce the noise
6
5
TRIM
V
OUT
10kΩ
OUTPUT
Rev. G | Page 6 of 12
NOISE PERFORMANCE AND REDUCTION
Noise generated by the AD587 is typically less than 4 µV p-p
over the 0.1 Hz to 10 Hz band. Noise in a 1 MHz bandwidth is
approximately 200 µV p-p. The dominant source of this noise is
the buried Zener, contributing approximately 100 nV/√Hz. By
comparison, the contribution of the op amp is negligible.
Figure 5 shows the 0.1 Hz to 10 Hz noise of a typical AD587.
The noise measurement is made with a band-pass filter made
of a 1-pole high-pass filter with a corner frequency at 0.1 Hz
and a 2-pole low-pass filter with a corner frequency at 12.6 Hz
to create a filter with a 9.922 Hz bandwidth.
If further noise reduction is desired, an external capacitor may
be added between the NOISE REDUCTION pin and ground, as
shown in Figure 4. This capacitor, combined with the 4 kΩ R
and the Zener resistances, forms a low-pass filter on the output
of the Zener cell. A 1 µF capacitor has a 3 dB point at 40 Hz and
reduces the high frequency (to 1 MHz) noise to about 160 µV
p-p. Figure 6 shows the 1 MHz noise of a typical AD587, both
with and without a 1 µF capacitor.
Figure 6. Effect of 1 µF Noise Reduction Capacitor on Broadband Noise
C
N
NO C
1µV
– 1µF
N
100
0%
90
10
100
0%
90
10
200µV
Figure 5. 0.1 Hz to 10 Hz Noise
1µV
50µs
5s
S