Datasheet

AD581
Rev. C | Page 6 of 12
APPLYING THE AD581
The AD581 is easy to use in virtually all precision reference
applications. The three pins are simply: primary supply, ground,
and output, with the case grounded. No external components
are required even for high precision applications; the degree of
desired absolute accuracy is achieved simply by selecting the
required device grade. The AD581 requires less than 1 mA quies-
cent current from an operating supply range of 13 V to 30 V.
+V
S
V
OUT
GND
AD581
10V
13V TO 30
V
08014-002
Figure 2. Pin Configuration (Bottom View)
An external fine trim may be desired to set the output level to
exactly 10.000 V within less than a millivolt (calibrated to a
main system reference). System calibration may also require a
reference slightly different from 10.00 V. In either case, the
optional trim circuit shown in Figure 3 can offset the output by
up to ±30 mV (with the 22  resistor), if needed, with minimal
effect on other device characteristics.
+V
S
V
OUT
6.8kΩ
10kΩ
4.3kΩ
GND
AD581
+10V
R
+15
V
–15V
R
TRIM
RANGE
MAX
Δ TCR
22Ω ±30mV 3.5ppm/°C
12Ω ±10mV 2.0ppm/°C
3.9Ω ±5mV 0.6ppm/°C
08014-003
Figure 3. Optional Fine Trim Configuration
V+
10V
V–
Q12
Q14
Q11
Q20
C52
Q6
Q16 Q13
C50
C51
Q10
R40 R41
Q7
Q8
Q15
R42
R34
R37
R35
R36R30
R31
R39
Q4Q3
Q5
Q1Q2
R32R33
0
8014-004
Figure 4. Simplified Schematic
VOLTAGE VARIATION vs. TEMPERATURE
Some confusion exists in the area of defining and specifying
reference voltage error over temperature. Historically, references
have been characterized using a maximum deviation per degree
Celsius; that is, 10 ppm/°C. However, because of nonlinearities
in temperature characteristics, which originated in standard
Zener references (such as S-type characteristics) manufacturers
opt for the maximum limit error band approach to specify devices.
This technique involves measurement of the output at three,
five, or more different temperatures to guarantee that the output
voltage falls within the given error band. The temperature charac-
teristic of the AD581 consistently follows the S-curve shown in
Figure 5. Three-point measurement of each device guarantees
the error band over the specified temperature range.
10.005
9.995
TEMPERATURE (°C)
V
OUT
(V)
10.000
–50–55 –40 –30 –20 –10 0 10 20 30 40 50 60 70 80 90 100 110 120 125
08014-005
Figure 5. Typical Temperature Characteristic