ADR440/ADR441/ADR443/ADR444/ADR445 Data Sheet
Rev. F | Page 16 of 18
Table 9. Digital Potentiometer Parts
Part No.
No. of
Channels
No. of
Positions ITF R (kΩ)
V
DD
1
(V)
AD5251 2.00 64.00 I
2
C 1, 10, 50, 100 5.5
AD5207 2.00 256.00 SPI 10, 50, 100 5.5
AD5242 2.00 256.00 I
2
C 10, 100, 1M 5.5
AD5262 2.00 256.00 SPI 20, 50, 200 15
AD5282 2.00 256.00 I
2
C 20, 50, 100 15
AD5252 2.00 256.00 I
2
C 1, 10, 50, 100 5.5
AD5232 2.00 256.00 SPI 10, 50, 100 5.5
AD5235 2.00 1024.00 SPI 25, 250 5.5
ADN2850 2.00 1024.00 SPI 25, 250 5.5
1
Can also use a negative supply.
Adding a negative supply to the operational amplifier allows
the user to produce a negative programmable reference
by connecting the reference output to the inverting terminal
of the operational amplifier. Choose feedback resistors to
minimize errors over temperature.
PROGRAMMABLE CURRENT SOURCE
It is possible to build a programmable current source using a
setup similar to the programmable voltage source, as shown in
Figure 38. The constant voltage on the gate of the transistor sets
the current through the load. Varying the voltage on the gate
changes the current. This circuit does not require a dual digital
potentiometer.
ADR440/
ADR441/
ADR443/
ADR444/
ADR445
V
IN
V
OUT
GND
I
LOAD
CC
R
SENSE
AD5259
2
6
4
0.1µF
0.1µF
05428-039
Figure 38. Programmable Current Source
HIGH VOLTAGE FLOATING CURRENT SOURCE
Use the circuit in Figure 39 to generate a floating current source
with minimal self heating. This particular configuration can
operate on high supply voltages, determined by the breakdown
voltage of the N-channel JFET.
ADR440/
ADR441/
ADR443/
ADR444/
ADR445
V
IN
V
OUT
GND
OP90
+
S
SST111
VISHAY
2N3904
–V
S
05428-040
2
6
4
Figure 39. Floating Current Source
PRECISION OUTPUT REGULATOR
(BOOSTED REFERENCE)
ADR440/
ADR441/
ADR443/
ADR444/
ADR445
6
2
V
IN
V
OUT
R
L
200Ω
C
L
1µF
2N7002
–V
15V
V
O
C
IN
0.1µF
C
OUT
0.1µF
IN
GND
4
5428-041
Figure 40. Boosted Output Reference
Higher current drive capability can be obtained without
sacrificing accuracy by using the circuit in Figure 40. The
operational amplifier regulates the MOSFET turn-on, forcing
V
O
to equal the V
REF
. Current is then drawn from V
IN
, allowing
increased current drive capability. The circuit allows a 50 mA
load; if higher current drive is required, use a larger MOSFET.
For fast transient response, add a buffer at V
O
to aid with
capacitive loading.
