AD5280BRUZ200 Analog Devices Inc, AD5280BRUZ200 Datasheet - Page 22

• Manufacturer Part Number: AD5280BRUZ200
• Description: IC,Digital Potentiometer,TSSOP,14PIN,PLASTIC
• Manufacturer: Analog Devices Inc

Specifications of AD5280BRUZ200

• Taps: 256
• Resistance (ohms): 200K
• Number Of Circuits: 1
• Temperature Coefficient: 30 ppm/°C Typical
• Memory Type: Volatile
• Interface: I²C, 2-Wire Serial
• Voltage - Supply: 4.5 V ~ 16.5 V, ±4.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 14-TSSOP
• Resistance In Ohms: 200K
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD5280/AD5282
PROGRAMMABLE CURRENT SOURCE
A programmable current source can be implemented with the
circuit shown in Figure 61.
headroom and high current handling precision reference that
can deliver 20 mA at 2.048 V. The load current is simply the
voltage across Terminal B to Terminal W of the digital
potentiometer divided by R
The circuit is simple, but attention must be paid to two things.
First, dual-supply op amps are ideal because the ground
potential of REF191 can swing from −2.048 V at zero scale to V
at full scale of the potentiometer setting. Although the circuit
works under single supply, the programmable resolution of the
system is reduced.
For applications that demand higher current capabilities, a
few changes to the circuit in Figure 61 produce an adjustable
current in the range of hundreds of milliamps. First, the voltage
reference needs to be replaced with a high current, low dropout
regulator, such as the ADP3333, and the op amp needs to be
swapped with a high current dual-supply model, such as the
AD8532. Depending on the desired range of current, an
appropriate value for R
current flowing to the load, the user must pay attention to the
load impedance so as not to drive the op amp beyond the
positive rail.
I
L
=
3
V
+5V
2
V
SLEEP
GND
–2.048V TO V
4
R
IN
REF
S
REF191
×
Figure 61. Programmable Current Source
×
2
AD5280
U
N
D
1
V
OUT
L
6
S
must be calculated. Because of the high
0 TO (2.048 + V
REF191
C1
1µF
S
.
V+
V–
OP8510
OP8510
+5V
5V
U2
U2
L
is a unique, low supply
B
A
)
W
100Ω
R
L
R
102Ω
S
V
L
I
L
Rev. C | Page 22 of 28
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L
PROGRAMMABLE BIDIRECTIONAL CURRENT
SOURCE
AD5280
For applications that require bidirectional current control or
higher voltage compliance, a Howland current pump can be a
solution (see Figure 62). If the resistors are matched, the load
current is
In theory, R2
current needed within the A
In this circuit, the
and the voltage compliance approaches 15 V. It can be shown
that the output impedance is
This output impedance can be infinite if Resistor R1' and
Resistor R2' match precisely with R1 and R2
respectively. On the other hand, it can be negative if the
resistors are not matched. As a result, C1 must be in the range
of 1 pF to 10 pF to prevent the oscillation.
I
Z
L
O
–5V
A
+5V
=
=
Figure 62. Programmable Bidirectional Current Source
W
(
R1
R2
B
×
R1
A
can be made as small as needed to achieve the
R2
R1
R2'
+
OP2177
'
+15V
–15V
×
B
R2
OP2177
V+
V–
R2
−
B
R1'
B
A
)
1
(
R1
×
(
R2
V
+
W
can deliver ±5 mA in either direction,
A
2
R2
150kΩ
output current driving capability.
+
R1
A
R2
150kΩ
)
R1
B
I
)
OP2177
+15V
–15V
15kΩ
R2
V+
V–
14.95kΩ
I
A
R2
+ R2
C1
10pF
A
A
2
B
,
R2
50kΩ
R
500kΩ
L
B
V
L
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L
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