AD5231BRUZ100-RL7 Analog Devices Inc, AD5231BRUZ100-RL7 Datasheet - Page 23

• Manufacturer Part Number: AD5231BRUZ100-RL7
• Description: IC,Digital Potentiometer,TSSOP,16PIN,PLASTIC
• Manufacturer: Analog Devices Inc

Specifications of AD5231BRUZ100-RL7

• Taps: 1024
• Resistance (ohms): 100K
• Number Of Circuits: 1
• Temperature Coefficient: 600 ppm/°C Typical
• Memory Type: Non-Volatile
• Interface: 4-Wire SPI Serial
• Voltage - Supply: 2.7 V ~ 5.5 V, ±2.25 V ~ 2.75 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-TSSOP
• Resistance In Ohms: 100K
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS
BIPOLAR OPERATION FROM DUAL SUPPLIES
The AD5231 can be operated from dual supplies ±2.5 V, which
enables control of ground referenced ac signals or bipolar
operation. AC signals as high as V
across Terminal A to Terminal B with output taken from
Terminal W. See Figure 46 for a typical circuit connection.
HIGH VOLTAGE OPERATION
The digital potentiometer can be placed directly in the feedback
or input path of an op amp for gain control, provided that the
voltage across Terminals A–B, Terminals W–A, or Terminals
W–B does not exceed |5 V|. When high voltage gain is needed,
users should set a fixed gain in an op amp operated at a higher
voltage and let the digital potentiometer control the adjustable
input. Figure 47 shows a simple implementation.
BIPOLAR PROGRAMMABLE GAIN AMPLIFIER
There are several ways to achieve bipolar gain. Figure 48 shows
one versatile implementation. Digital potentiometer U1 sets the
adjustment range; the wiper voltage V
programmed between V
linear adjustment, configure A2 as a noninverting amplifier and
the transfer function becomes
where:
K is the ratio of R
D is the decimal equivalent of the input code.
µC
V
GND
DD
V
V
O
I
SCLK
=
MOSI
SS
⎛
⎜
⎝
AD5231
Figure 46. Bipolar Operation from Dual Supplies
1
+
R2
R1
Figure 47. 15 V Voltage Span Control
WB
⎞
⎟
⎠
/R
5V
×
A
B
CS
CLK
SDI
GND
WA
⎛
⎜
⎝
AD5231
W
1024
R
i
D
that is set by U1.
and −KV
2
×
1 (
–
+
A1
+
DD
i
V
V
2.2pF
15V
K
2R
at a given U2 setting. For
DD
SS
V+
V–
C
/V
W
A
B
C
)
W2
−
SS
±1.25V p-p
can, therefore, be
K
can be applied directly
0V TO 15V
⎞
⎟
⎠
D = MIDSCALE
V
O
±2.5V p-p
+2.5V
–2.5V
Rev. C | Page 23 of 28
(4)
In the simpler (and much more usual) case where K = 1,
a pair of matched resistors can replace U1. Equation 4 can be
simplified to
Table 20 shows the result of adjusting D with A2 configured as a
unity gain, a gain of 2, and a gain of 10. The result is a bipolar
amplifier with linearly programmable gain and 1024-step
resolution.
Table 20. Result of Bipolar Gain Amplifier
D
0
256
512
768
1023
10-BIT BIPOLAR DAC
If the circuit in Figure 48 is changed with the input taken from a
voltage reference and A2 configured as a buffer, a 10-bit bipolar
DAC can be realized. Compared to the conventional DAC, this
circuit offers comparable resolution but not the precision
because of the wiper resistance effects. Degradation of the
nonlinearity and temperature coefficient is prominent near
both ends of the adjustment range. On the other hand, this
circuit offers a unique nonvolatile memory feature that in some
cases outweighs any shortfall in precision.
The output of this circuit is
Vi
V
V
V
AD5231
AD5231
O
O
I
=
=
U2
U1
R1 = ∞, R2 = 0
−1
−0.5
0
0.5
0.992
⎛
⎜
⎝
⎛
⎜
⎝
Figure 48. Bipolar Programmable Gain Amplifier
1
1024
2
A
A
+
D
R2
R1
2
W
B
W
B
−
OP2177
A
⎞
× ⎟
⎠
1
⎞
× ⎟
⎠
V+
V–
⎛
⎜
⎝
V
V
DD
1024
SS
2
V
D
REF
2
−
1
⎞
⎟
⎠
–KVi
R1 = R2
−2
−1
0
1
1.984
A2
OP2177
V+
V–
V
V
DD
SS
R2
R1
R2 = 9 × R1
−10
−5
0
5
9.92
AD5231
C
2.2pF
C
V
O
(5)
(6)