ADR550_15 Datasheet, PDF (12/16 Pages) Analog Devices – High Precision Shunt Mode Voltage References

ADR520/ADR525/ADR530/ADR540/ADR550
Stacking the ADR520/ADR525/ADR530/ADR540/ADR550
for User-Definable Outputs
Multiple ADR520/ADR525/ADR530/ADR540/ADR550 parts
can be stacked to allow the user to obtain a desired higher voltage.
Figure 22 shows three ADR550s configured to give 15 V. The bias
resistor, RBIAS, is chosen using Equation 3; note that the same
bias current flows through all the shunt references in series.
Figure 23 shows three ADR550s stacked to give −15 V. RBIAS
is calculated in the same manner as before. Parts of different
voltages can also be added together. For example, an ADR525
and an ADR550 can be added together to give an output of
+7.5 V or −7.5 V, as desired. Note, however, that the initial
accuracy error is now the sum of the errors of all the stacked
parts, as are the temperature coefficients and output voltage
change vs. input current.
+V_DD
R
+15V
ADR550
ADR550
ADR550
GND
Figure 22. +15 V Output with Stacked ADR550s
GND
R
ADR550
ADR550
ADR550
–15V
–V_DD
Figure 23. −15 V Output with Stacked ADR550s
Adjustable Precision Voltage Source
The ADR520/ADR525/ADR530/ADR540/ADR550, combined
with a precision low input bias op amp, such as the AD8610,
can be used to output a precise adjustable voltage. Figure 24
illustrates the implementation of this application using the
ADR520/ADR525/ADR530/ADR540/ADR550. The output
of the op amp, VOUT, is determined by the gain of the circuit,
which is completely dependent on the resistors, R1 and R2.
VOUT = VREF (1 + R2/R1)
An additional capacitor, C1, in parallel with R2, can be added to
filter out high frequency noise. The value of C1 is dependent on
the value of R2.
V_S
R
V_REF
ADR5xx
AD8610
R2
V_OUT = V_REF (1+R2/R1)
R1
GND
C1
(OPTIONAL)
Figure 24. Adjustable Voltage Source
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