ADR5040/ADR5041/ADR5043/ADR5044/ADR5045
Data Sheet
Adjustable Precision Voltage Source
Programmable Current Source
The ADR5040/ADR5041/ADR5043/ADR5044/ADR5045,
combined with a precision low input bias op amp such as the
AD8610, can be used to output a precise adjustable voltage.
Figure 22 illustrates the implementation of this application
using the ADR5040/ADR5041/ADR5043/ADR5044/ADR5045.
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.
By using just a few ultrasmall and inexpensive parts, it is possible
to build a programmable current source, as shown in Figure 23.
The constant voltage on the gate of the transistor sets the current
through the load. Varying the voltage on the gate changes the
current. The AD5247 is a digital potentiometer with I2C® digital
interface, and the AD8601 is a precision rail-to-rail input op
amp. Each incremental step of the digital potentiometer increases
or decreases the voltage at the noninverting input of the op amp.
Therefore, this voltage varies with respect to the reference
voltage.
V
OUT = (1 + R2/R1)VREF
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
DD
R
R
SENSE
BIAS
V
CC
R
BIAS
V
REF
ADR5040/
ADR5041/
ADR5043/
ADR5044/
ADR5045
V
= V (1 + R2/R1)
REF
AD8610
R2
OUT
ADR5040/ADR5041/
ADR5043/ADR5044/
ADR5045
V+
AD8601
V–
AD5247
R1
I
LOAD
C1
(OPTIONAL)
GND
Figure 22. Adjustable Voltage Source
Figure 23. Programmable Current Source
Rev. B | Page 12 of 16
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