ADR525 Analog Devices, ADR525 Datasheet - Page 12

• Manufacturer Part Number: ADR525
• Description: High Precision Shunt Mode Voltage References
• Manufacturer: Analog Devices

ADR520/ADR525/ADR530/ADR540/ADR550
Stacking ADR5xx for User-Definable Outputs
Multiple ADR5xx parts can be stacked together to allow the
user to obtain a desired higher voltage. Figure 22a shows three
ADR550s configured to give 15 V. The bias resistor, R
chosen using Equation 3, noting that the same bias current will
flow through all the shunt references in series. Figure 22b shows
three ADR550s stacked together to give –15 V. R
in the same manner as before. Parts of different voltages can
also be added together, i.e., 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 tempco and output
voltage change versus input current.
R
+V
GND
(a)
Figure 22. 15 V Output with Stacked ADR550s
DD
ADR550
ADR550
ADR550
+15V
GND
R
–V
(b)
DD
ADR550
ADR550
ADR550
–15V
BIAS
is calculated
BIAS
, is
Rev. A | Page 12 of 16
Adjustable Precision Voltage Source
The ADR5xx, combined with a precision low input bias op amp,
such as the AD8610, can be used to output a precise adjustable
voltage. Figure 23 illustrates the implementation of this
application using the ADR5xx. The output of the op amp, V
is determined by the gain of the circuit, which is completely
dependant on the resistors, R1 and R2 .
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.
ADR5xx
R
V
BIAS
REF
GND
V
CC
Figure 23. Adjustable Voltage Source
R1
V
OUT
AD8610
(OPTIONAL)
= (1 + R2/R1 ) V
R2
C1
V
REF
OUT
= V
REF
(1+R2/R1)
OUT
,